Biotypes of Corynebacterium Diphtheriae

Biotypes of Corynebacterium diphtheriae

Corynebacterium diphtheriae is a nonmotile, noncapsulated, club-shaped, gram-positive bacillus. Toxigenic strains are lysogenic for one of a family of corynebacteriophages that carry the structural gene for diphtheria toxin, tox. Corynebacterium diphtheriae is classified into biotypes (mitis, intermedius, and gravis) according to colony morphology, as well as into lysotypes based upon corynebacteriophage sensitivity. McLeod and Anderson …

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Difference between O Antigen and H Antigen

Difference between O Antigen and H Antigen

The antigen used to define serological test of Salmonella include Somatic O antigen, Flagellar H antigen and Vi antigen (Capsular antigen). Some of the differences between O Antigen and H Antigen are as follows: S.N. Characteristics O Antigen H Antigen 1. Types Somatic Antigen Flagellar antigen 2. Composition Polysaccharide Proteinaceous 3. Antibody formation Rapid and …

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Difference between S. pneumoniae and Viridans Streptococci

Difference between S. pneumoniae and Viridans Streptococci

S.N. Characteristics S. pneumoniae Viridans Streptococci 1. Morphology Lanceolate diplococci Oval or round cells in chain 2. Capsule Capsulated Non-capsulated 3. Quellung Test Positive Negative 4. Bile solubility Bile soluble Bile insoluble 5. Inulin fermentation Positive Negative 6. Optochin sensitivity Sensitive Resistant 7. Pathogenicity in mice Pathogenic Non-pathogenic 8. Hemolysis Alpha-hemolytic (under aerobic conditions) or …

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Rapid Plasma Reagin (RPR) Test for the diagnosis of Syphilis

Rapid Plasma Reagin (RPR) Test for the diagnosis of Syphilis

Rapid plasma reagin (RPR) is macroscopic, non treponemal, flocculation card test used to screen for syphilis caused by Treponema pallidum. RPR is simple test can be done within few minutes. This test is less sensitive than treponemal test in early syphilis infection. Two types of antibodies are produced in syphilis i.e. autoantibody (cardiolipin) response and …

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Scrub Typhus- Etiology, Epidemiology, Symptoms, Pathogenesis, Diagnosis and Treatment

Scrub Typhus- Etiology, Epidemiology, Symptoms, Pathogenesis, Diagnosis and Treatment

Scrub Typhus is an acute febrile illness which is caused by an obligate intracellular pathogen called Orientia tsutsugamushi, which is transmitted by the bite of infected larval stage trombiculid mite, Leptotrombidium spp. (Chiggers). The name scrub typhus was applied after discovery of increased frequency of the disease in scrub or wasteland areas. Etiology of Scrub …

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Mannitol Salt Agar for the isolation of Staphylococcus aureus

Mannitol Salt Agar for the isolation of Staphylococcus aureus

Mannitol Salt Agar (MSA) is used as a selective and differential medium for the isolation and identification of Staphylococcus aureus from clinical and non-clinical specimens. It encourages the growth of a group of certain bacteria while inhibiting the growth of others. It is a selective medium prepared according to the recommendations of Chapman for the …

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CAMP Test- Principle, Uses, Procedure and Result Interpretation

CAMP Test- Principle, Uses, Procedure and Result Interpretation

CAMP test is used to distinguish the species Streptococcus agalactiae from other species of beta-hemolytic Streptococcus. S. agalactiae, a member of the Lancefield Group B streptococci, is one of the causative agents of mastitis in cows. CAMP is an acronym for the authors of this test (Christie, Atkinson, Munch, and Peterson) which was identified in …

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Difference between Anthrax Bacilli and Anthracoid Bacilli

Difference between Anthrax Bacilli and Anthracoid Bacilli

S.N. Characteristics Anthrax Bacilli Anthracoid Bacilli 1. Motility Non-Motile Generally Motile 2. Capsule Capsulated Non-Capsulated 3. Shape Grow in long chains Grow in short chains 4. Medusa Head Colony Present Not Present 5. Growth in Penicillin Agar (10 units/ml) No Growth Grow Usually 6. Hemolysis Hemolysis absent or weak. Usually well marked 7. Gelatin Liquefaction …

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Virulence Factors of Staphylococcus

Virulence Factors of Staphylococcus

A.   Cell Wall Associated Virulence Factors Functions Peptidoglycan – Pyrogenicity – Complement Activation – Inhibition of leukocyte migration Techoic Acid – Adherence to mucosal surfaces Capsule – Diffusion Barrier – Prevents Phagocytosis – Capsular serotypes 5 and 8 are most frequently associated with bacteremia and infections B.   Cell Surface Associated Virulence Factors Functions Protein A …

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Difference between Neisseria gonorrhoeae and Neisseria meningitidis

Difference between Neisseria gonorrhoeae and Neisseria meningitidis

Neisseria gonorrhoeae and Neisseria meningitidis are both Gram Negative Bacteria. They are diplococci, non-sporing, non-motile and oxidase positive. But they have some differences which are as follows: S.N. Characteristics Neisseria gonorrhoeae Neisseria meningitidis 1 Referred as Referred to as gonococcus. Referred to as meningococcus. 2 Agents N. gonorrhoeae is the agent of gonorrhoea. N. meningitidis …

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Differences Between Staphylococcus and Streptococcus

Differences Between Staphylococcus and Streptococcus

Staphylococcus and Streptococcus are both Gram positive organisms and cocci in shape. They are Non-motile, Non-Sporing and Facultative anaerobes. But they possess some of the differences which are as follows: S.N Characteristics Staphylococcus Streptococcus 1 Arrangement Grape-like clusters. A chain of round cells. 2 Division Staphylococci divide in various directions (multiple axes). Division occurs in one linear direction (single …

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Lowenstein-Jensen (LJ) Medium- Composition, Principle, Uses, Preparation and Colony Morphology

Colony Morphology on LJ Medium

Lowenstein-Jensen (LJ) is the selective medium which is used for the cultivation and isolation of Mycobacterium species. It was developed by Lowenstein who incorporated congo red and malachite green to inhibit unwanted bacteria. The present formulation, a glycerated egg-based medium, is based upon Jensen’s modification. Jensen’s version eliminates congo red and uses a moderate concentration of malachite green …

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Optochin Susceptibility Test for the identification of Streptococcus pneumoniae

Result Interpretaion of Optochin Susceptibility Test

Differentiation of Streptococcus pneumoniae from other viridans streptococci depends on demonstrating optochin susceptibility, bile solubility, reaction with a specific DNA probe, or detection of species-specific capsular polysaccharides. Most clinical microbiology laboratories today depend on the optochin susceptibility test. Although optochin susceptibility was first described for differentiating pneumococci from other α-hemolytic streptococci in 1915, the test …

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Differences Between Exotoxins and Endotoxins

Differences Between Exotoxins and Endotoxins

Many bacteria produce toxins, enzymes and pigments. Toxins and enzymes play important role in pathogenecity. Toxins are of two types: Exotoxins are usually heat labile proteins secreted by certain species of bacteria which diffuse into the surrounding medium. Endotoxins are heat stable lipopolysaccharide-protein complexes which form structural components of cell wall of Gram Negative Bacteria …

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Differences between Gram Positive and Gram Negative Bacteria

Differences between Gram Positive and Gram Negative Bacteria

S.N. Characteristics Gram Positive Gram Negative 1 Gram Reaction Retain crystal violet dye and stain blue or purple Can be decolorized to accept counterstain (safranin) and stain pink or red 2 Cell Wall Cell Wall is 20-30 nm thick. Cell Wall is 8-12 nm thick. 3 Cell Wall The wall is Smooth. The wall is …

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Different Size, Shape and Arrangement of Bacterial Cells

Different Size, Shape and Arrangement of Bacterial Cells

Bacteria are prokaryotic, unicellular microorganisms, which lack chlorophyll pigments. The cell structure is simpler than that of other organisms as there is no nucleus or membrane bound organelles. Due to the presence of a rigid cell wall, bacteria maintain a definite shape, though they vary as shape, size and structure. When viewed under light microscope, …

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Haemolysis of Streptococci and its types with examples

Haemolysis of Streptococci and its types with examples

Hemolysis is the breakdown of red blood cells (RBC). A substance that causes hemolysis is a hemolysin. Brown (1919) introduced three terms alpha, beta and gamma to indicate three types of streptococci based on haemolytic reactions observed on blood agar plates. Beta-hemolytic Streptococci Beta-hemolysis (β-hemolysis) is associated with complete lysis of red cells surrounding the colony. Beta …

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Haemophilus influenzae: Habitat, Cell Morphology, Cultural Characteristic, Biochemical Tests, Pathogenicity, Diagnosis and Treatment

Haemophilus influenzae

Habitat Mucous membrane of the upper respiratory tract of humans. Found in the nasopharynx of approx. 75% of healthy peoples. Cell Morphology Slender, short, gram negative rods or coccobacillus 3-0.5 um X 0.5-1 um with rounded ends. Prolonged counterstaining for 5-15 minutes with very dilute carbol fuschin often gives satisfactory results. Non-Motile, No flagella or …

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