Bacteria – classification, Definition, structure, Types, examples, diseases

Questions Related to microbiology & Bacteria – EduLesson

Bacteria are classified into five groups according to their basic shapes: spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochaetes). They can exist as single cells, in pairs, chains or clusters. Bacteria are found in every habitat on Earth: soil, rock, oceans and even arctic snow. Bacteria are classified into five groups according to their basic shapes: spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochaetes). They can exist as single cells, in pairs, chains or clusters. Bacterial growth is proliferation of bacterium into two daughter cells, in a process called binary fission. Providing no event occurs, the resulting daughter cells are genetically identical to the original cell. Hence, bacterial growth occurs. Both daughter cells from the division do not necessarily survive. There are three notable common traits of bacteria, 1) lack of membrane-bound organelles, 2) unicellular and 3) small (usually microscopic) size. Not all prokaryotes are bacteria, some are archaea, which although they share common physicals features to bacteria, are ancestrally different from bacteria.


Pili and inclusion of Volutin in bacteria.

Pili are small hairs that enable some pathogens to attach and adhere easily to cell surface particularly mucous membranes. Bacteria possessing pili include  Neisseria gonorrhea and some strains of Escherichia coli, Salmonella, and Shigella species.,

Granules of Valyutin –Volutin. intracellular inclusions in microorganisms; a temporary reserve of nutrients similar to fatty inclusions and glycogen granules in animals. Volutin is strained by basic dyes. It is usually composed of high-molecular polyphosphates and less commonly of poly-β-hydroxybutyric acid or other compounds.

Types of pili –Fimbriae (pili) are shorter, straighter and more numerous than bacterial flagella and are composed by subunits of protein called pilin.

Types: Two general types of Pili are known they are:

 a) Sex pili (long conjugation pili or F pili) and.

 b) Common pili (short attachment pili also called fimbriae).

The composition of pili– The fimbriae and pili have a shaft composed of a protein called pilin.

Pili function – They can have a role in movement, but are more often involved in adherence to surfaces, which facilitates infection and is a key virulence characteristic.

Volutin granules – chemical composition and functions – Volutiintracellular inclusions in microorganisms; a temporary reserve of nutrients similar  to fatty inclusions and  glycogen granules in animals. Volutin is strained by basic dyes. It is usually  composed of high-molecular polyphosphates and less commonly of poly-β-hydroxybutyric acid or other compounds.

Methods for staining Volutin inclusions (name the bacterium containing volutin granules)–  Polyphosphate granules display the metachromatic effect, appearing red when stained with methylene blue  and  Differential staining techniques commonly used in clinical settings include Gram staining, acid-fast staining, endospore staining, flagella staining, and capsule staining.

Example– a) Corynebacterium diphtheriae, b) Yersinia pestis, and c) Mycobacterium tuberculosis.

Capsules and spores of bacteria

Indicate capsule – The bacterial capsule is a very large structure of many bacteria. It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell. It is a well-organized layer, not easily washed off, and it can be the cause of various diseases. in the figure.

The composition and properties of the capsule – It usually consists of polysaccharides, but can be composed of other materials such as glycoprotein, polypeptide D-glutamic acid in B. anthracis, and peptidoglycan and muramic acid found in E. coli bacterial capsule.

Function of the capsule – The capsule is considered a virulence factor because it enhances the ability of bacteria to cause disease (e.g. prevents phagocytosis). The capsule can protect cells from engulfment by eukaryotic cells, such as macrophages. A capsule-specific antibody may be required for phagocytosis to occur.

Capsule staining methods (Examples of capsule-forming microorganisms) – Capsule staining can be done by two methods, namely positive and negative staining methods. Positive staining method either stain a capsule only or can stain both the capsule and bacterial cell. Negative staining method stains both the bacterial cell and its background.

The capsule is found most commonly among gram-negative bacteria:

·      Escherichia coli (in some strains)

·      Neisseria meningitidis.

·      Klebsiella pneumoniae.

·      Haemophilus influenzae.

·      Pseudomonas aeruginosa.

·      Salmonella.

Method of staining spores in bacteria – A differential staining technique (the Schaeffer-Fulton method) is used to distinguish between the vegetative cells and the endospores. A primary stain (malachite green) is used to stain the endospores.

Examples of spore-forming bacteria –

Types of Spore Forming Bacteria

·Bacillus : Anthrax and Research. Bacillus is a genus of spore forming, aerobic, rod-shaped bacteria.

·Clostridium : Disease and Production.

·Sporolactobacillus : Lactic Acid Makers.

·Sporosarcina: Breaking down Urine.


Flagella of bacteria

Indicate flagella – Flagella are long, thin, whip-like appendages attached to a bacterial cell that allow for bacterial movement. Some bacteria have a single flagellum, while others have many flagella surrounding the entire cell.

This type of movement is called chemotaxis and is how a bacterium uses its flagellum to find food.

Flagella composition – The bacterial flagellum is made up of the protein flagellin. Its shape is a 20-nanometer-thick hollow tube. It is helical and has a sharp bend just outside the outer membrane; this “hook” allows the axis of the helix to point directly away from the cell.

Structure of flagella – A bacterial flagellum has 3 basic parts: a filament, a hook, and a basal body. 1) Filament: it is thin hair like structure arises from hook. 2) Hook: it is the wider region at the base of filament, it connects filament to the motor protein in the base, length of hook is longer in gram +ve bacteria than gram –ve bacteria. 3) Basal body: it is composed of central rod inserted into series of rings which is attached to cytoplasmic memvbrane and cell wall.

§L-ring: it is the outer ring present only in Gram -ve bacteria, it anchored in lipopolysaccharide layer

§P-ring: it is second ring anchored in peptidoglycan layer of cell wall.

§M-S ring: anchored in cytoplasmic membrane

§C ring: anchored in cytoplasm

Functions of flagella – flagella provide movement and propulsion. 

Methods for the detection of flagella –Two techniques for staining flagella are in use: a)  A wet-mount procedure (Ryu method)b) Dried-smear preparation (Leifson staining technique)

An example of monotrich – (Monotrichous) – Single polar flagellum – Example: Vibrio cholerae 

An example of peritrich ( Peritrichous) – Numerous falgella all over the bacterial body – Example: Salmonella Typhi

 The cell wall of Bacteria

Give a detailed description of the presented cell wall – both in structure, in composition and function – Peptidoglycan is made up of a polysaccharide backbone consisting of alternating N-Acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) residues in equal amounts. Peptidoglycan is responsible for the rigidity of the bacterial cell wall and for the determination of cell shape.cell wall is a layer located outside the cell membrane found in plants, fungi, bacteria, algae, and archaea. A peptidoglycan cell wall composed of disaccharides and amino acids gives bacteria structural support. The bacterial cell wall is often a target for antibiotic treatment.  the cell wall is composed of peptidoglycanGram positive bacteria have cell walls composed of thick layers of peptidoglycan. Gram positive cells stain purple when subjected to a Gram stain procedure and teichonic acid ;- teichonc acid  is a major  surface  antigen of gram positive bacteria containing ribitol or glycerol polymers Gram negative bacteria have cell walls with a thin layer of peptidoglycan.

Cell wall function – The primary function of the cell wall is to maintain the shape and integrity of the cell in the face of high osmotic pressurecell wall are to provide structure, support, and protection for the cell.

The staining method used to differentiate the cell wall – Gram staining is a bacteriological laboratory technique used to differentiate bacterial species into two large groups (Gram-positive and Gram-negative) based on the physical properties of their cell walls.

What is protoplast – Protoplasts and spheroplasts are altered forms of bacteria or yeast , in which the principal shape-maintaining structure of the bacteria is weakened. The term protoplast refers to the spherical shape assumed by Gram-positive bacteria. Spheroplast refers to the spherical shape assumed by Gram-negative bacteria.

The term protoplast refers to the spherical shape assumed by Gram-positive bacteria. Spheroplast refers to the spherical shape assumed by Gram-negative bacteria. The difference is essentially the presence of a single membrane, in the case of the protoplast, and the two membranes (inner and outer) of the Gram-negative spheroplasts. It is also possible to generate a gram-negative protoplast by the removal of the outer membrane. Thus, in essence, protoplast refers to a bacterial sphere that is bounded by a single membrane and spheroplast refers to a sphere that is bounded by two membranes.

What is a spheroplast – Spheroplast refers to the spherical shape assumed by Gram-negative bacteria. The difference is essentially the presence of a single membrane, in the case of the protoplast, and the two membranes (inner and outer) of the Gram-negative spheroplasts. It is also possible to generate a gram-negative protoplast by the removal of the outer membrane. Thus, in essence, protoplast refers to a bacterial sphere that is bounded by a single membrane and spheroplast refers to a sphere that is bounded by two membranes.

Nature of the growth of microorganisms (Bacteria)

     Growth Requirements for Microorganisms. A characteristic of microorganisms is their ability to grow and form a population of organisms. One of the results of microbial metabolism is an increase in the size of the cell. The many requirements for successful growth include those both chemical and physical. the growth of bacteriahave 4 phase . In batch culture can be modeled with four different phases: lag phase (A), log phase or exponential phase (B), stationary phase (C), and death phase (D).

Bacterial growth is proliferation of bacterium into two daughter cells, in a process called binary fission. Providing no event occurs, the resulting daughter cells are genetically identical to the original cell. Indicate which in the figure.

Facultative anaerobes because – An organism which is capable of producing energy through aerobic respiration and then switching back to anaerobic respiration depending on the amounts of oxygen and fermentable material in the environment. Example: – Staphylococcus spp., Streptococcus spp., Escherichia coli, Salmonella, Listeria spp., Shewanella oneidensis and Yersinia pestis.

Obligatory anaerobes, because – Obligate anaerobes are organism which can only live in environments which lack oxygen. Example: – obligately anaerobic bacterial genera include Actinomyces, Bacteroides, Clostridium, Fusobacterium, Peptostreptococcus, Porphyromonas, Prevotella, Propionibacterium, and Veillonella.

Microaerophiles, because ;-Microaerophiles need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen. They gather in the upper part of the test tube but not the very top. Example: –Campylobacter species are microaerophilic.Helicobacter pylori, a species of proteobacteria

Aero tolerant because;-  Aerotolerant organisms do not require oxygen as they metabolise energy anaerobically. Unlike obligate anaerobes however, they are not poisoned by oxygen. They can be found evenly spread throughout the test tube.

Obligatory aerobes because;-Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest.

Antibiotics according to their mechanism of action :  

Penicillin G, Amoxicillin, Flucloxacillin, Cefoxitin,  Cefotaxime, Ceftriaxone, Imipenem, Norfloxacin, Ciprofloxacin, Enoxacin,  Ofloxacin, Gentamicin, Amikacin, Tetracycline, Sulphonamides, Rifamycinum

Inhibits bacterial cell wall synthesis– Penicillin G, Amoxicillin, Flucloxacillin, Cefoxitin, Cefotaxime, Ceftriaxone, Imipenem,

Inhibits bacterial protein synthesis– Gentamicin, Amikacin, Tetracycline,

Blocks bacterial cell metabolism by inhibiting enzymes– Sulphonamides, , Rifamycinum

Inhibits bacterial DNA replication and synthesis– Norfloxacin , Ciprofloxacin , Enoxacin, ,  Ofloxacin

Inhibits the synthesis of bacterial mRNA– Amikacin,

 A Clinical Question on Infection of Bacteria

    The infectious process is (give definition) – Infection is the invasion of an organism’s body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxins they produce. The six links include: the  infectious agent, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host.

1.How to determine the incubation period – The time from the moment of exposure to an infectious agent until signs and symptoms of the disease appear. For example, the incubation period of chickenpox is 14-16 days. In biology, the incubation period is the time needed for any particular process of development to take place.

Transmission ways for various  infection – 

  1. Direct contact is person-to-person transmission of pathogens through touching, biting, kissing, or sexual intercourse.
  2. Indirect contact
    1. Airborne transmission: – Some infectious agents can travel long distances and remain suspended in the air for an extended period of time. …
    2. Contaminated objects. …
    3. Food and drinking water. …
    4. Animal-to-person contact. …
    5. Animal reservoirs. …
    6. Insect bites (vector-borne disease) …
    7. Environmental reservoirs.

Source of infection – Man as a source: A person can be the source of infection in the following cases: 

  1. During the incubation period of a disease– in some infections the agent is secreted during the incubation period this is important as the infection is usually not known (e.g. Hep A and B).
  2. Sick man– in clinical, abortive ( short and mild without usual pronounced clinical symptoms) , atypical or apparent forms. 
  3. Convalescent – secretion of agents occurs during convalescence (gradual recovery of health and strength after illness) ie. as in pertussis. 
  4. Carriers– short term ( salmonalla), long term ( typhoid fever) or intermittent (secretions at certain certain periods)

Patient as source : via airbornevia bloodbornesexually transmitteddirect contactfecal oral transmission

Define what an epidemic is – An epidemic is the rapid spread of infectious disease to a large number of people in a given population within a short period of time, usually two weeks or less. For example, in meningococcal infections, an attack rate in excess of 15 cases per 100,000 people for two consecutive weeks is considered an epidemic.

Infectious Disease Prevention – Preventing the Spread of Infectious Diseases, Wash your hands often, Get vaccinated, Use antibiotics sensibly, Stay at home if you have signs and symptoms of an infection, Be smart about food preparation, Disinfect the ‘hot zones’ in your residence, Practice safer sex, Don’t share personal items.

Features of morphology and cultural properties of bacteria

Spherical bacteria – A coccus (plural cocci) is any bacterium or archaeon that has a spherical, ovoid, or generally round shape. EXAMPLE ;- Streptococcus pneumoniae, Moraxella catarrhalis, Neisseria gonorrhea. 

(Streptococcus pneumoniae and Neisseria gonorrhoeaeStreptococci are chains of cocci (e.g. Streptococcus pyogenes). Staphylococci are irregular (grape-like) clusters of cocci (e.g. Staphylococcus aureus). Rod-shaped bacteria _ A bacillus (plural bacilli) or bacilliform bacterium is a rod-shaped bacterium or archaeon . Diplobacilli: Two bacilli arranged side by side with each other. Streptobacilli: Bacilli arranged in chains. Coccobacillus: Oval and similar to coccus (circular shaped bacterium). Examples of Gram positive bacilli: – ActinomycesBacillusClostridiumCorynebacteriumListeriaPropionibacteriumExamples of Gram negative bacilli: – BacteroidesCitrobacterEnterobacterEscherichiaKlebsiellaPseudomonasProteusSalmonellaSerratiaShigellaVibrioYersinia.

Inoculation method according to Drigalsky – Spread plate technique (Superficial dispersions by Drigalsky’s technique) is more perfect method which is widely in everyday microbiological practice. There is quantitative technique that allows the determination of the number of bacteria in a sample.

Stages: Pipette the required amount of bacteria (from your dilution) on the     surface of the Petri plate. 2) Spread the inoculum over the surface of the agar medium using a hockey stick (spatula). 3) Repeat this action on 3-4 Petri plates without sterilization of the hockey stick. 4) Incubate the plate inverted at 37 oC.

Gould’s inoculation method – Gould’s S1 media are often used for the isolation, enumeration and diversity evaluation of £uorescent Pseudomonas .The selectivity of Gould’s S1 medium is based on an iron limitation, and high glycerol and sucrose contents.It is also based on other compounds such as sodium lauroyl sarcosine (which inhibits the growth of Gram-positive bacteria) and trimethoprim (an antibiotic limiting the growth of non-£uorescent Pseudomonas.

forms of colonies S – type – Common examples are Entire (S)(smooth), irregular, Undulate (wavy), Lobate, Curled, Filiform etc. Colonies that are irregular in shape and/or have irregular margins are likely to be motile organisms. Highly motile organism swarmed over the culture media.

Methods for detecting the structural components of a bacterial cell.


Purpose Gram methods – Gram staining is a common technique used to differentiate two large groups of bacteria based on their different cell wall constituents. The Gram stain procedure distinguishes between Gram positive and Gram negative groups by coloring these cells red or violet.

Purpose of  Burri-Gins methods

The purpose of the methods Romanovsky – Giemsa – Giemsa stain is a type of Romanowsky stain, named after Gustav Giemsa, a German chemist who created a dye solution. It was primarily designed for the demonstration of malarial parasites in blood smears, but it is also employed in histology for routine examination of blood smear.

Uses of Giemsa Stain: – Apart from staining malarial parasites, Giemsa stain has a variety of applications in Microbiology and Pathology:

  • Giemsa stain is used to obtain differential white blood cell counts.
  • It is also used to differentiate nuclear and cytoplasmic morphology of the various blood cells like platelets, RBCs, WBCs.
  • In Microbiology, Giemsa stain is used for staining inclusion bodies in Chlamydia trachomatisBorrelia species, and if Wayson’s stain is not available, to stain Yersinia pestis. Giemsa stain also is used to stain Histoplasma capsulatumPneumocystis jiroveci,Klebsiella granulomatis, Penicillium marneffei and occasionally bacterial capsules.
  • This stain is also used in cytogenetics to stain the chromosomes and identify chromosomal aberrations. It is commonly used for G-banding (Giemsa-Banding)

Purpose of the Ozheska method  The cytoplasmic membrane plays the role of an osmotic barrier that controls …. For coloring spores, the Ozheska method is used, based on their acid resistance.

The purpose of the Ziel – Nielsen method – ZiehlNeelsen (ZN) method of Acid Fast staining technique is used to stain Mycobacterium species including M. tuberculosis, M. Ulcerans .The cellwall of Mycobacteria contain high concentration of lipid making them waxy, hydrophobic, and impermeable to routine stain such as the Gram Stain.

Organisms such as Mycobacteria are extremely difficult to stain by ordinary methods like Gram Stain because of the high lipid content of the cell wall. The phenolic compound carbol fuchsin is used as the primary stain because it is lipid soluble and penetrates the waxy cell wall.

Sterilization, disinfection, aseptic and antiseptic. Antibiotics.

Definitions of sterilization –Sterilization: Killing or removing all forms of microbial life (including endospores) in a material or an object. Heating is the most commonly used method of sterilization.Usually involves the removal of vegetative or non-endospore forming pathogens.

Definitions of disinfection – Water disinfection means the removal, deactivation or killing of pathogenic microorganisms. Microorganisms are destroyed or deactivated, resulting in termination of growth and reproduction.Sterilization is a process related to disinfection.

Definitions of aseptic – Bacteria, viruses, and other microorganisms that cause disease are called pathogens.Aseptic technique means using practices and procedures to prevent contamination from pathogens. It involves applying the strictest rules to minimize the risk of infection.

Definitions of antiseptics –antiseptic. noun. Definition of antiseptic (Entry 2 of 2) : a   substance that inhibits the growth or action of microorganisms especially in or on living tissue clean the wound with an antiseptic also : germicide.

What are the methods used to determine the sensitivity of microorganisms to antibiotics – Tests for antibiotic sensitivity include:

  1. Kirby-Bauer method. Small wafers containing antibiotics are placed onto a plate upon which bacteria are growing
  2. Stokes method
  3. Etest (also based on antibiotic diffusion)
  4. Agar and Broth dilution methods for minimum inhibitory concentration (MIC) determination.  

S aureus belongs to staphylococcus

Morphology and tinctorial properties ;-Saureus is a facultatively anaerobic, Gram-positive coccus, which appears as grape-like clusters when viewed through a microscope, and has round, usually golden-yellow colonies, often with hemolysis, when grown on blood agar plates.

Cultural properties;-

  1. culture media;-Staph. aureus will grow on general culture media such as Blood Agar and chocolated Blood Agar and therefore can be isolated from direct plating of clinical specimens. More specialised media, such as Staph/Strep Selective Medium contain antimicrobials.
  2. cultivation conditions ;- Growth conditionsTemperature range: 4-46 °C (39-115°F) for growth and toxin production. Optimum Temperature: 37°C (98.6°F) pH range: 4.8-8.0.

Virulence factors;- The virulence factors of Staphylococcus aureus include antigens, enzymes and toxins like: -Antigens: – Capsule, Adhesins. Enzymes: – Coagulase, Lipase, Hyaluronidase, Staphylokinase.

Principles and features of the laboratory Diagnostics;- Laboratory diagnosis: – Gram staining: Gram positive cocci in clusters is the characteristics, cocci may appear singly in pairs or in short chains.

Yellow colonies of S. aureus in Mannitol Salt Agar 

Culture: – 

  1. Blood Agar:  growth occurs abundantly within 18 to 24 hours, yellow or golden yellow colonies with or without Beta hemolysis are seen. 
  2. Mannitol Salt Agar (MSA)  is a selective media  commonly used for the isolation of S. aureus. After inoculation, MSA plates were incubated at 35°C for 24 to 48 hours. S. aureus is Mannitol fermenting bacteria and gives yellow or gold colonies. 

Biochemical tests: 

Diseases caused by S aureus;- S. aureus can cause a range of illnesses, from minor skin infections, such as pimples, impetigo, boils, cellulitis, folliculitis, carbuncles, scalded skin syndrome, and abscesses, to life-threatening diseases such as pneumonia, meningitis, osteomyelitisendocarditis, toxic shock syndrome, bacteremia, and sepsis.

Streptococcuspyogenes – streptococci

Morphology and tinctorial properties;- The individual cocci are spherical or ovoid, 0.5-1 µm in diameter and are arranged in chains. The length of chain vary widely with cultural conditions. Larger chain are formed in liquid or broth than in solid agar. Streptococci are gram positive but they may become gram negative in ageing when bacteria die. 

Cultural properties:

  1. culture media ;- Streptococci are generally grown on agar media supplemented with blood. Selective media for culturing Gram-positive bacteria (such as agar media that contains phenylethyl alcohol, or Columbia agar with colistin and nalidixic acid) also provide adequate culturing conditions for S. pyogenes. 
  2. cultivation conditions ;- S. pyogenes is a facultative anaerobe and is grown at 37°C in either ambient air or in 5–10% CO2. Like all streptococci, GAS is both catalase and oxidase negative. pyogenes (GAS) in alternative environments such as chemically defined medium, low glucose and peptide rich medium, and human blood are also described. Ph-7.5 

Virulence factors ;- Virulence factors of Group A streptococci include: (1) M protein, fibronectin-binding protein (Protein F) and lipoteichoic acid for adherence; (2) hyaluronic acid capsule as an immunological disguise and to inhibit phagocytosis; M-protein to inhibit phagocytosis (3) invasins such as streptokinase, streptodornase (DNase…) 

Principles and features of the laboratory Diagnostics;-

  1. Gram Staining (Gram positive cocci in chains)
  2. Catalase Test (Negative)Culture on Blood Agar
  3. β-Hemolysis): – Grown anaerobically, 100% of strains are beta-hemolyticGrown aerobically, 85% of strains are beta hemolytic (15% are non-hemolytic)two hemolysins (streptolysins) – O and S O = encoded by 100% of strains; O2 labileS = encoded by 85% of strains; O2 stable
  4. Bacitracin sensitivity test (Sensitive)
  5. Pyrrolidonyl Arylamidase (PYR) Test (+ve): 

Diseases caused by Streptococcus pyogenes ;-Diseases caused by S.pyogenes Mnemonic: Diseases caused by Streptococcus pyogenes : NIPPLES: Necrotising fasciitis and myositis, Impetigo, Pharyngitis, Pneumonia, Lymphangitis, Erysipelas and cellulitis, Scarlet fever/ Streptococcal TSS


Morphology and tinctorial properties; Mycobacterium tuberculosis is a fairly large nonmotile rod-shaped bacterium distantly related to the Actinomycetes. Many non pathogenic mycobacteria are components of the normal flora of humans, found most often in dry and oily locales. The rods are 2-4 micrometers in length and 0.2-0.5 um in width.

Cultural properties – 

  1. culture media; The Löwenstein–Jensen medium, more commonly known as LJ medium, is a growth medium specially used for culture of Mycobacterium species, notably Mycobacterium tuberculosis. When grown on LJ mediumMtuberculosis appears as brown, granular colonies (sometimes called “buff, rough and tough”). 
  2. cultivation conditions;- tuberculosis must acquire sufficient Mg2+ in order to grow in a mildly acidic environment such as within the phagosome of macrophages. Mtuberculosis grows within the phagocytic vacuoles of macrophages (2), where it is exposed to a relatively hostile environment.

Virulence factors ;- PDIM and PLG are major virulence factors of mycobacteria. PDIM and PGL are molecules required for bacterial duplication during the acute phase . PDIM is involved in mycobacterial resistance to detergents, and also is linked with the permeability and envelope solidity

Principles and features of the laboratorydiagnostics;– The Mantoux tuberculin skin test (TST) or the TB blood test can be used to test for Mtuberculosis infection. Additional tests are required to confirm TB disease. The Mantoux tuberculin skin test is performed by injecting a small amount of fluid called tuberculin into the skin in the lower part of the arm. 

Diseases caused by ; Examples of diseases spread from faeces: Campylobacter infection. Cryptosporidium infection. Giardia infection. hand, foot and mouth disease. hepatitis A. meningitis (viral), rotavirus infection. Salmonella infection.

Brucella melitensis

Morphology and tinctorial properties;- Brucella melitensis is a Gram-negative coccobacillus bacterium from the Brucellaceae family. The bacterium causes ovine brucellosis, along with Brucella ovis. It can infect sheepcattle, and sometimes humans, and it can be transmitted by the stable fly. It is zoonotic, unlike B. ovis, causing Malta fever or localized brucellosis in humans.

Cultural properties – 

  1. culture media;- BD Brucella Agar with 5% Horse Blood is used for the isolation and growth of fastidious and nonfastidious bacterial species, including Brucella, from clinical and nonclinical specimens. 
  2. cultivation conditions ;-In a rich medium with yeast extract, all Brucella species grew at 18 degrees C and 42.5 degrees (except one) while most B. suis (14/17) grew also at 15 degrees C and 44 degrees C, in contrast to other brucellae of which a few strains only grew at these temperatures. 

Principles and features of the laboratory Diagnostics ;- Doctors usually confirm a diagnosis of brucellosis by testing blood or bone marrow for the brucella bacteria or by testing blood for antibodies to the bacteria. To help detect complications of brucellosis, your doctor may order additional tests, including: X-rays. The alternate methods predominantly include serological tests such as enzyme-linked immunosorbent assay, serum agglutination testing and molecular tests with varying advantages and drawbacks suited to various clinical situations . 

Diseases caused by Brucella melitensis;-This disease is known as ovine brucellosis, and is a reportable disease in the USA. In goats and sheep, B. melitensis can cause abortion, stillbirth, and weak offspring for the first gestation after the animal is infected. Mastitis can happen, but is uncommon. The infection can also reduce milk yield by at least 10%. (human disease/animal disease): Malta fever/Bang’s disease, Undulant fever/enzootic abortion, Mediterranean fever/epizootic abortion, Rock fever of Gibraltar/slinking of calves, Gastric fever/ram epididymitis, Contagious abortion/spontaneous abortion.

Corynebacterium diphtheriae

Morphology and tinctorial properties: –Corynebacterium diphtheriae is the bacterium that causes the disease diphtheriaCorynebacterium diphtheriae is a rod-shaped, Gram positive, non spore-forming, and nonmotile bacterium.The portals of entry for Corynebacterium diphtheriae are the nose, tonsils, and throat. Bacteriology.  And the usually with one end being wider, thus giving the often-described club-shaped appearance. On culture, particularly under suboptimal conditions, characteristic bands or granules appear.

Cultural properties –

  1. culture media;- The clinical diagnosis of diphtheria requires bacteriologic laboratory confirmation of toxigenic C diphtheriae in throat or lesion cultures. For primary isolation, a variety of media may be used: Loeffler agar, Mueller-Miller tellurite agar, or Tinsdale tellurite agar.
  2. cultivation conditions ;- Most strains require nicotinic and pantothenic acids for growth; some also require thiamine, biotin, or pimelic acid. For optimal production of diphtheria toxin, the medium should be supplemented with amino acids and must be deferrated. Temp –optimum – 37 c (range , 15 – 40). pH – 7.2  

Virulence factors ;- The main virulence factor of C. diphtheriae is diphtheria toxin (DT), an exotoxin, released by the bacteria after entering the human body. DT is classified as an AB toxin because it has two components, one for activation and one for binding.

Principles and features of the laboratory diagnostics;- Corynebacterium diphtheriae – Diphtheria. Classic diphtheria is characterized by the formation of a pseudomembrane on respiratory mucous membranes. Initial testing includes CBC and a rapid strep test. A diphtheria culture is usually diagnostic if disease symptoms are present. They can use a swab from the back of the throat and test it for the bacteria that cause diphtheria. A doctor can also take a sample from a skin lesion (like a sore) and try and grow the bacteria. If the bacteria grow, the doctor can be sure a patient has diphtheria. They can use a swab from the back of the throat and test it for the bacteria that cause diphtheria. A doctor can also take a sample from a skin lesion (like a sore) and try and grow the bacteria. If the bacteria grow, the doctor can be sure a patient has diphtheria

Diseases caused by Corynebacterium diphtheria;- Diphtheria is an infection caused by the bacterium Corynebacterium diphtheriae. Diphtheria causes a thick covering in the back of the throat. It can lead to difficulty breathingheart failureparalysis, and even death. CDC recommends vaccines for infants, children, teens and adults to prevent diphtheria.

Salmonella enterica serotype typhi

Morphology and tinctorial properties;- Salmonella enterica serovar Typhi is a gram-negative, rod-shaped facultative anaerobe that only infects humans. It is unclear to scientists as to why this pathogen does not infect other organisms and has such a selective host behavior. Salmonella has adapted to grow under both an aerobic and anaerobic conditions. Salmonella’s most common source of electron acceptors is nitrogen. Examples of other electron acceptors are: nitrate, nitrite, fumarate, and dimethlysulphoxide.

Cultural properties ;-

  1. culture media;- The most commonly used media selective for Salmonella are SS agar, bismuth sulfite agar, Hektoen enteric (HE) mediumMacConky agar , brilliant green agar and xylose-lisine-deoxycholate (XLD) agar.Salmonella serotype Typhimurium (phage type DT104) and Salmonella serotype Enteritidis (phage types 4, 8, and 13) were used in cell culture infection experiments and routinely grown on modified Luria-Bertani (LB) broth or agar and xylose lysine deoxycholate (XLD) agar at 37°C.
  2. cultivation conditions;- Salmonella species lead predominantly host-associated lifestyles, but the bacteria were found to be able to persist in a bathroom setting for weeks following contamination, and are frequently isolated from water sources, which act as bacterial reservoirs and may help to facilitate transmission between hosts.Salmonella is notorious for its ability to survive desiccation and can persist for years in dry environments and foods. pH 6-8 , temp – 15- 41 ( optimium – 37 c ). 

Virulence factors ;- Many of the Salmonella virulence factors, such as adhesion, invasion, and toxin genes are clustered in certain areas of the chromosome known as “Salmonella pathogenicity islands” (SPI).

Principles and features of the laboratory diagnostics;- Salmonella infection can be detected by testing a sample of your stool. However, most people have recovered from their symptoms by the time the test results return. If your doctor suspects that you have a salmonella infection in your bloodstream, he or she may suggest testing a sample of your blood for the bacteria. Diagnosing Salmonella infection requires testing a specimen (sample), such as stool (poop) or blood. Testing can help guide treatment decisions. Infection is diagnosed when a laboratory test detects Salmonella bacteria in stool, body tissue, or fluids. 

Diseases caused by Salmonella enterica serotype typhi;- The differential diagnosis of those infected with Salmonella enterica serotype typhi should include: Malaria, Q fever, Amebiasis, Leptospirosis, Dengue fever, Yellow fever, Leishmaniasis, Filariasis, Viral hemorrhagic fever.

Yersinia pestis

Morphology and tinctorial properties;-General characteristicsYpestis is a nonmotile, stick-shaped, facultative anaerobic bacterium with bipolar staining (giving it a safety pin appearance) that produces an antiphagocytic slime layer. Similar to other Yersinia species, it tests negative for urease, lactose fermentation, and indole. Yersinia pestis is a oval  , rod shaped gram-negative bacteria that can also have a spherical shape. It is also covered by a slime envelope that is heat labile. When the bacteria is in a host, it is nonmotile (incapable of self-propelled movement), but when isolated it is motile

Cultural properties

  1. culture media ;-  according to Current WHO regulations for isolation of Ypestis recommend the use of brain heart infusion agar (BHIA), sheep blood agar, and MacConkey agar . However, since MacConkey medium was originally developed for isolation of enteric bacteria in general, it allows growth of a large number of gram-negative organisms.
  2. cultivation conditions The Ypestis strains were grown on solid medium for 48 h at 5°C, 10°C, or 40°C or for 24 h at 15°C to 37°C. pH –( 5-9.6 ) optimium , – 7.2 temp;-  2 – 45 c   the optimum temperature  for the growth (unlike most pathogens ) is 27 c but the envelope develops best at 37 c. 

Virulence factors The anti-phagocytic antigens Factor 1 (F1) and V-antigen (LcrV) also contribute to the virulence of Ypestis. The bacterium exports F1, and it is assembled into a capsule-like structure. LcrV also increases resistance to phagocytosis as well as downregulation of the inflammatory response.

Principles and features of the laboratory diagnostics If your doctor suspects plague, he or she may look for the Yersinia pestis bacteria in samples taken from your: Buboes. If you have the swollen lymph nodes (buboes) typical of bubonic plague, your doctor may use a needle to take a fluid sample from them (aspiration). BloodIf your doctor suspects plague, he or she may look for the Yersinia pestis bacteria in samples taken from your: A) Buboes. If you have the swollen lymph nodes (buboes) typical of bubonic plague, your doctor may use a needle to take a fluid sample from them (aspiration). B) Blood. You’ll generally have Yersinia pestis bacteria present in your bloodstream only if you have septicemic plague. C) Lungs. To check for pneumonic plague, your doctor will take mucus (sputum) or fluid from your airways using a thin, flexible tube inserted through your nose or mouth and down your throat (endoscopy). 

Diseases caused byYersinia pestis ;- It causes the disease plague, which takes three main forms: pneumonicsepticemic, and bubonic plagues.


Morphology and tinctorial properties;- C. tetani is a bacillus (rod-shaped) gram positive bacterium, which means it possess a thick cell wall made up of multiple layers of peptidoglycan and one inner membrane. C. tetani are motile bacteria and move by the means of rotary flagellum in the peritrichous orientation. Clostridium tetani is a motile, anaerobic, spore forming bacteria ( terminal spores with drum stick appearance) Footnote 1, Footnote 2. Vegetative cells are rod shaped, pleomorphic, and occur in pairs or short chains Footnote.

Cultural properties

  1. culture media ;-Ctetani can be grown on various anaerobic growth media such as thioglycolate media, casein hydrolysate media, and blood agar. Cultures grow particularly well on media at a neutral to alkaline pH, supplemented with reducing agents.
  2. cultivation conditions ;- C. tetani cannot grow in the presence of oxygen. It grows best at temperatures ranging from  33 to 37°C. Upon exposure to various conditionsCtetani spores are extremely hardy and are resistant to heat, various antiseptics, and boiling for several minutes. pH – 7 – 7.4 .

Virulence factors ;- Virulence FactorsCtetani produces two exotoxins, tetanolysin and tetanospasmin, which are encoded by plasmid born genes. Tetanospasmin is a neurotoxin, which is similar to botulinum toxin in structure and mode of action, but they act on different parts of the nervous system. 

Principles and features of the laboratory diagnostics;- The laboratory diagnosis of tetanus involves the isolation and identification of Ctetani and the detection of toxigenicity in the isolate by mouse toxicity testing. The latter is the definitive test for the laboratory diagnosis of tetanus

Diseases caused by Clostridiumtetani;- Tetanus, also called lockjaw, is a serious infection caused by Clostridium tetani. This bacterium produces a toxin that affects the brain and nervous system, leading to stiffness in the muscles. If Clostridium tetani spores are deposited in a wound, the neurotoxin interferes with nerves that control muscle movement .

Treponema pallidum

Morphology and tinctorial properties ;- Treponema pallidum is a spirochaete bacterium with various subspecies that cause the diseases syphilis, bejel, and yaws. It is transmitted only amongst humans. It is a helically coiled microorganism usually 6–15 μm long and 0.1–0.2 μm wide. 

Cultural properties-

  1. culture media ;- Treponema pallidum, cannot be cultured, and there is no single optimal alternative test. Serological testing is the most frequently used approach in the laboratory diagnosis of syphilis.The stage of the disease at which the patient presents has implications for diagnosis and treatment.
  2. Cultivation conditions;- They are found in the human oral cavity, gastrointestinal tracts of humans, mammals, insects, and in marine environments. Effects of temperature and/or pH on VlsE expression in vitro. Spirochetes (B31) were cultured in BSK-H medium at 24 ° C and pH 7.5 (24, 7.5), 34 ° C and pH 7.0 (34, 7), or 34 ° C and pH 8.0.

Virulence factors ;The Tpallidum genome sequence does not reveal any obvious classical virulence factors that could account for syphilis signs and symptoms. Tpallidum lacks lipopolysaccharide (LPS) (105), the endotoxin found in the outer membranes of many gram-negative bacteria that causes fever and inflammation. 

Principles and features of the laboratory diagnostics;- Direct diagnostic methods include the detection of T pallidum by microscopic examination of fluid or smears from lesions, histological examination of tissues or nucleic acid amplification methods such as polymerase chain reaction (PCR). Indirect diagnosis is based on serological tests for the detection of antibodies.

Diseases caused by Treponemapallidum;Treponema pallidum is a spirochaete bacterium with various subspecies that cause the diseases syphilisbejel, and yaws.

Flu Infectious Agents

Morphology and tinctorial properties ;- Influenza is caused by infection of the respiratory tract with influenza viruses, RNA viruses of the Orthomyxovirus genus. Influenza viruses are classified into 4 types: A, B, C, and D. Only virus types A and B commonly cause illness in humans. The flu is a common infectious disease caused by influenza (flu) viruses. The flu usually affects a person’s breathing system. Seasonal flu generally occurs in the fall and winter and is caused by human influenza viruses

Cultural properties – 

  1. culture media ;- 
  2. cultivation conditions ;- Depending on environmental conditions (e.g. humidity and temperature), however, it can survive up to several hours and in water at low temperatures (e.g. <20 °C) also considerably longer (up to several months). Influenza viruses are sensitive to lipid solvents and detergents. They are also vulnerable to heat and a low pH, depending on the virus type. Influenza A viruses with uncleaved HA are obviously more stable (loss of infectivity at pH <4.5) than viruses with cleaved HA (loss of infectivity at pH <5).

Virulence factors ;- Viral culture is a laboratory test in which samples are placed with a cell type that the virus being tested for is able to infect. If the cells show changes, known as cytopathic effects, then the culture is positive. Traditional viral culture has been generally superseded by shell vial culture, in which the sample is centrifuged onto a single layer of cells and viral growth is measured by antigen detection methods. This greatly reduces the time to detection for slow growing viruses such as cytomegalovirus, for which the method was developed. 

Principles and features of the laboratory diagnostics: – Laboratory Diagnostic Procedures A number of tests can help in the diagnosis of influenza.Diagnostic tests available for influenza include viral culture, serology, rapid antigen testing, reverse transcription polymerase chain reaction (RT-PCR), immune fluorescence assays, and rapid molecular assays. 

Diseases caused by influenza ;- nfluenza, commonly known as the flu, is an infectious disease caused by an influenza virus. Symptoms can be mild to severe. The most common symptoms include: high fever, runny nose, sore throat, muscle and joint pain, headache, coughing, and feeling tired.

Distribute antibiotics according to their mechanism of action: Penicillin G, Amoxicillin, Flucloxacillin, Cefoxitin, Cefotaxime, Ceftriaxone, Imipenem, Norfloxacin, Ciprofloxacin, Ofloxacin, Gentamicin, Amikacin, Tetracycline, Sulphamamides, Sulphamamin

Inhibits the synthesis of the bacterial cell wall: – Penicillin G, Amoxicillin, Flucloxacillin, Cefoxitin, Cefotaxime, Ceftriaxone, Imipenem,  

Inhibits bacterial protein synthesis: – Tetracycline, Gentamicin,  

It blocks the metabolism of bacterial cells by inhibiting enzymes :- Sulphamamides, Sulphamamin 

Inhibits bacterial DNA synthesis: – Norfloxacin, Ciprofloxacin, Ofloxacin,  

Inhibits RNA synthesis: – Amikacin,

Hepatitis D virus (HDV);

1. Explain why this virus cannot reproduce on its own ;- Virus do not have their own enzyme systemthat why  Viruses can only replicate themselves by infecting a host cell and therefore cannot reproduce on their own. A primary reason is that viruses do not possess a cell membrane or metabolise on their own – characteristics of all living organisms.

2. Routes of transmission of HDV  – HDV is transmitted by the same methods as HBV: exposure to infected blood and serous body fluids; and contaminated needles, syringes, blood and plasma product transfusions. Sexual transmission may also occur but is less common than with HBV. 

3. Material for research – A team of researchers has discovered how one crucial step occurs in the lifecycle of the hepatitis D virus (HDV), which causes the widespread and hard to treat liver inflammation called hepatitis D. The study, which was published recently in the Journal of Virology, could help develop antiviral therapy to control this disease. 

4. Methods of laboratory (microbiological) diagnosis of HDV – Laboratory Testing: – Diagnosis. Hepatitis D virus (HDV) RNA. Presence of anti-HDV antibodies. Test only HBV-positive patients. Testing. HDV total antibodies (IgG and IgM) Qualitative only. Can be used in acute or chronic HDV. Confirms presence of HDV in individual with chronic HBV infection. Polymerase chain reaction (PCR) test. 

5. Is HbS antigen a marker for HDV- Serologic markers of hepatitis B virus (HBV) and hepatitis D virus infection in carriers of hepatitis B surface antigen who are frequently exposed to HBV.Serologic evidence of HDV infection was detected in 35% of drug addicts, 50% of thalassemia patients and in 9.4% of hemodialysis patients.Hepatitis D Virus (HDV) causes accelerated liver diseases in patients with Hepatitis B Virus (HBV) infection. There is lack of data about its prevalence, related risk factors and interaction with HBV carriers in our country.

Respiratory syncytial virus is the main cause of bronchiolitis and community-acquired pneumonia in newborns.

1. Describe the virus genome: –Human respiratory syncytial virus (HRSV), known to be a leading cause of severe respiratory infections in neonates and children, belongs to the Pneumovirus genus within the family Paramyxoviridae (1). HRSVs have enveloped, negative-sense, single-stranded RNA genomes of approximately 15 kb that encode 11 viral proteins. 

2. Virus taxonomy: –RSV is a single-stranded RNA enveloped virus of the family Paramyxoviridae, genus Pneumovirus; it is related to human metapneumovirus. 

3. Routes of transmission of the virus: – it is in direct contact with the environment and its continually exposed to microorganisms suspended in the air. 

4. Laboratory diagnostic methods: –Respiratory syncytial virus (RSV) can be detected by rapid antigen detection tests (RADTs), direct fluorescent antibody (DFA) and polymerase chain reaction (PCR) testing, and culture. If RSV is the main concern, DFA testing or RADTs may be used, particularly in infants and children. 

5. Specific prevention: – Cover your coughs and sneezes with a tissue or your upper shirt sleeve, not your hands, Wash your hands often with soap and water for 20 seconds, Avoid close contact, such as kissing, shaking hands, and sharing cups and eating utensils, with others. Avoid close contact with sick peoples, Wash their hands often with soap and water

Avoid touching their face with unwashed hands, Limit the time they spend in child-care centers or other potentially contagious settings, especially during fall, winter, and spring. This may help prevent infection and spread of the virus during the RSV season.


1. Describe the genome of the virus: –a single-stranded, linear RNAgenome coated by nucleocapsid proteins (NP) in association with an RNA polymerase complex of both large (L) and phosphoprotein (P) sub units. It has been estimated that over 2,000 such NP molecules coat the genome along with about 250 P and 25 L molecules. 

2. Virus taxonomy: –Rubulavirus is a former genus of viruses in the family Paramyxoviridae, order Mononegavirales. Humans, apes, pigs, and dogs serve as natural hosts. There are currently 17 species in the two genera Orthorubulavirus and Pararubulavirus. Diseases associated with this genus include mumps

3. Routes of transmission of the virus: – The transmission mode is person to person via respiratory droplets and saliva, direct contact, or fomites. 

4. Laboratory diagnostic methods: –RT-PCR and viral culture are used to confirm mumps infection. Buccal swabs are most commonly used for RT-PCR testing, but urine and CSF may also be used in specific situations. IgM serology can also be used to aid in diagnosing mumps infection. 

5. Specific prevention: – The most common preventive measure against mumps is a vaccination with a mumps vaccine, invented by American microbiologist Maurice Hilleman at Merck. The vaccine may be given separately or as part of the MMR vaccine given between 12-15 months old or MMRV vaccine given between the age 4 -6.

Whooping cough

1. Describe the morphology of the bacterium: – Bordetella pertussis is a Gram-negative, aerobic, pathogenic, encapsulated coccobacillus of the genus Bordetella, and the causative agent of pertussis or whooping cough. Like B. bronchiseptica, B. pertussis is motile and expresses a flagellum-like structure. 

2. Features of the cultivation of bacteria: –pertussis is motile and expresses a flagellum-like structure. Its virulence factors include pertussis toxin, adenylate cyclase toxin, filamentous hæmagglutinin, pertactin, fimbria, and tracheal cytotoxin. The bacterium is spread by airborne droplets; its incubation period is 7–10 days on average (range 6–20 days). 

3. Routes of transmission: –Pertussis spreads from person to person. People with pertussis usually spread the disease to another person by coughing or sneezing or when spending a lot of time near one another where you share breathing space. 

4. Laboratory diagnostic methods: –Clinicians commonly use several types of  laboratory tests to diagnose Bordetella pertussis. Scientists consider culture the gold standard because it is the only 100% specific method for identification. Other tests that can be performed include polymerase chain reaction (PCR) and serology. 

5. Specific prevention: –The best way to prevent pertussis (whooping cough) among babies, children, teens, and adults is to get vaccinated. Also, keep babies and other people at high risk for pertussis complications away from infected people. In the United States, the recommended pertussis vaccine for babies and children is called DTaP.

Filatov-Koplik spots are on the mucosa of the buccal surface and upper palate. Preliminary diagnosis: “Measles, catarrhal period of development”?

1. Describe the virus genome: – Measles virus is a spherical, nonsegmented, single-stranded, negative-sense RNA virus and a member of the Morbillivirus genus in the family of Paramyxoviridae. The measles virus RNA genome consists of approximately 16,000 nucleotides and is enclosed in a lipid-containing envelope derived from the host cell. 

2. Virus taxonomy: –Measles morbillivirus, formerly called measles virus (MeV), is a single-stranded, negative-sense, enveloped, non-segmented RNA virus of the genus Morbillivirus within the family Paramyxoviridae. It is the cause of measles. Humans are the natural hosts of the virus; no animal reservoirs are known to exist. 

3. Routes of transmission of the virus: – Measles is a highly contagious virus that lives in the nose and throat mucus of an infected person. It can spread to others through coughing and sneezing. Also, measles virus can live for up to two hours in an airspace where the infected person coughed or sneezed.

4. Laboratory diagnostic methods: – Detection of measles-specific IgM antibody in serum and measles RNA by real-time polymerase chain reaction (RT-PCR) in a respiratory specimen are the most common methods for confirming measles infection. For people unable to have their blood drawn, saliva can be collected for salivary measles-specific IgA testing.  

5. Specific prophylaxis:– Measles can be prevented with measles-containing vaccine, which is primarily administered as the combination measles-mumps-rubella (MMR) vaccine.

Microscopy of the cerebrospinal fluid revealed a large number of neutrophils containing bean-shaped diplococci.

1. Describe the morphology of the bacterium: – A diplococcus (plural diplococci) is a round bacterium (a coccus) that typically occurs in the form of two joined cells. Examples of gram-negative diplococci are Neisseria spp., Moraxella catarrhalis, and Acinetobacter spp. Examples of gram-positive diplococci are Streptococcus pneumoniae and Enterococcus spp.

2. Features of the cultivation of bacteria – Thayer-Martin agar (or Thayer-Martin medium) is a Mueller-Hinton agar with 5% chocolate sheep blood and antibiotics. It is used for culturing and primarily isolating pathogenic Neisseria bacteria, including Neisseria gonorrhoeae and Neisseria meningitidis, as the medium inhibits the growth of most other microorganisms

.3. Routes of transmission – A diplococcus (plural diplococci) is a round bacterium (a coccus) that typically occurs in the  N. gonorrhea is transmitted through copulation with a person who is infected. 

4. Laboratory diagnostic methods –Diagnostic Tests – The useful typing methods for determining strain relatedness include auxotyping, serotyping, plasmid profile analysis, DNA sequencing of the porB gene and pulsed-field gel electrophoresis. Quality assurance programs for diagnostic testing and antimicrobial susceptibility testing is reviewed. 

5. Specific prevention Keep the germs away: 1) Wash your hands before eating, or touching your eyes, nose or mouth. 2) Wash your hands after touching anyone who is sneezing, coughing or blowing their nose. 3) Don’t share things like towels, lipstick, toys, or anything else that might be contaminated with respiratory germs.


1. Describe the morphology of the bacterium: – Salmonella are gram-negative, rod-shaped bacilli that can cause salmonellosis, a diarrheal illness in humans. Gram-negative bacteria usually have a cell wall composed of a thin layer of peptidoglycan, covered by a membrane. 

2. Features of the cultivation of bacteria – Xylose Lysine Deoxycholate agar (XLD agar) is a selective growth medium used in the isolation of Salmonella and Shigella species from clinical samples and from food. It has a pH of approximately 7.4, leaving it with a bright pink or red appearance due to the indicator phenol red.

3. Routes of transmission – Mode of transmission of Salmonella,Transmission is usually person-to-person or animal-to-person via the faecal–oral route, through ingestion of the organisms via contaminated or improperly cooked foods. Foodborne transmission occurs particularly with: raw and undercooked eggs and egg products.

4. Laboratory diagnostic methods – Salmonella infection can be detected by testing a sample of your stool. If your doctor suspects that you have a salmonella infection in your bloodstream, he or she may suggest testing a sample of your blood for the bacteria. 

5. Specific prevention – Avoid eating raw or barely cooked eggs. Don’t eat raw or undercooked beef, pork, or poultry. Refrigerate food properly, both before cooking it and after serving it. Wash your hands well with soap and warm water before, and after, handling food.

On the eve of the disease was at a party where he ate canned home-made mushrooms. Based on clinical symptoms, a diagnosis of Botulism was made.

1. Describe the morphology of the bacterium –Clostridium botulinum is a gram-positive bacteria that is typically rod-shaped and arranged as singles, pairs, or chains. C. botulinum lies dormant in the form of spores until the right environmental conditions are met. These spores are very resistant to adverse environmental effects, making them amenable to most environments and very hard to kill. The spores will grow under favorable conditions (anaerobiosis and substrate-rich environments) and will begin to produce their toxins as they rapidly propagate. 

2. Features of the cultivation of bacteria –Conditions that favor botulism include a high-moisture, low-salt, low-acid environment in which food is stored without oxygen or refrigeration. Anaerobic conditions can develop in canned foods, smoked fish, sausages and some cooked foods. 

3. Routes of transmission – Botulism is not transmitted from person to person. Botulism develops if a person ingests the toxin (or rarely, if the toxin is inhaled or injected) or if the organism grows in the intestines or wounds and toxin is released. Food-borne botulism is spread by consuming food contaminated with the botulism toxin or spores.

4. Laboratory diagnostic methods- The routine laboratory diagnostics of botulism is based on the detection of botulinum neurotoxin in the patient. Detection of toxin-producing clostridia in the patient and/or the vehicle confirms the diagnosis. The neurotoxin detection is based on the mouse lethality assay. 

5. Specific prevention- To prevent the occurrence of this bacterium in processed foods, many companies can their food with a pressurized boil to kill the bacterium with high temperatures. Other techniques include high levels of oxygen, high acidity, high ratio of dissolved sugar, or very low levels of moisture.

The foot dangled. Preliminary diagnosis: “Paralytic form of poliomyelitis”?

1. Describe the genome of the virus Poliovirus is composed of an RNA genome and a protein capsid. The genome is a single-stranded positive-sense RNA genome that is about 7500 nucleotides long. Polio, or poliomyelitis, is a disabling and life-threatening disease caused by the poliovirus. 

2. Taxonomy of the virus Poliovirus is a member of the picornavirus viral family, a taxonomic grouping that includes rhino viruses and hepatisis A virus.  

3. Routes of transmission of the virus – Wild poliovirus is spread through faeces and saliva. It is primarily transmitted through faecal–oral spread and is an important consideration where sanitation is poor. ‘Live’ oral polio vaccine (OPV) virus can be shed in the faeces for 6 weeks and may lead to infection in unvaccinated contacts. 

4. Laboratory diagnostic methods – Poliovirus can be detected in specimens from the throat, feces (stool), and occasionally cerebrospinal fluid (CSF) by isolating the virus in cell culture or by detecting the virus by polymerase chain reaction (PCR). CDC laboratories conduct testing for poliovirus, including: Culture. 

5. Specific prevention – Provision of clean water, improved hygienic practices and sanitation are important for reducing the risk of transmission in endemic countries. Immunisation is the cornerstone of polio eradication. Two types of vaccine are available: an inactivated poliovirus vaccine (IPV) and a live attenuated OPV.

Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria,Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria, Bacteria,