All Free Microbiology MCQs with Answers

• A. Tissue culture
• B. Chick embryos
• C. Artificial media
• D. Rabbit testis only

Explanation: Pathogenic Treponema pallidum cannot be grown on ordinary artificial media and is classically maintained by passage through rabbit testes.

• A. Mycoplasma
• B. Mycobacteria
• C. Spirochaete
• D. Chlamydia

Explanation: Borrelia vincentii is a spiral-shaped bacterium, so it belongs to the spirochaetes.

• A. Gram staining
• B. Fermentation of mannitol and sorbital
• C. Production of intracellular and extracellular adherent polysacharide
• D. Colony morphology on saliva agar

Explanation: Gram staining cannot distinguish Streptococcus mutans from other oral streptococci because all are Gram-positive cocci.

• A. Pasturella spp
• B. Francisella spp
• C. Bartonella spp
• D. Brucella spp

Explanation: Brucella is a small Gram-negative coccobacillus associated with animal exposure and is oxidase positive, often requiring special culture…

• A. Type of hemolysis
• B. Gram staining
• C. Growth characteristics
• D. Bile solubility

Explanation: Streptococcus pneumoniae is identified among alpha-haemolytic streptococci by its bile solubility, along with optochin sensitivity and a…

• A. M Protein
• B. Cultural characteristics
• C. Bile Solubility
• D. Cell wall carbohydrate

Explanation: The major Lancefield classification of streptococci is based on antigenic differences in cell-wall carbohydrate.

• A. Foot paid on nine branded armadilo
• B. Tail of guinea pig
• C. Testes of albino rats
• D. Testes of guinea pig

Explanation: Mycobacterium leprae cannot be grown on artificial culture media and is experimentally propagated in the footpads of the nine-banded…

• A. Ziel Nelson
• B. Kin Young stain
• C. Auramine-Rhodamine stain
• D. Giemsa stain

Explanation: Auramine-rhodamine staining uses fluorescence to detect acid-fast bacilli and can screen a larger smear area more rapidly than…

• A. M. leprae
• B. M. avium intracellulare
• C. M. tuberculosis
• D. Kansasi

Explanation: Mycobacterium tuberculosis causes the commonest mycobacterial infection worldwide, including tropical countries. M.

• A. Theta toxin
• B. Lecithinase
• C. Desmolase
• D. Cytokinin

Explanation: Lecithinase, or alpha toxin, hydrolyses lecithin in egg-yolk media and produces an opaque, opalescent zone around Clostridium perfringens…

• A. Clostridium tetani
• B. Clostridium welchii
• C. Coli
• D. Strep. Faecalis

Explanation: Gas gangrene is classically caused by Clostridium perfringens, formerly called Clostridium welchii.

• A. Multiply within living cell
• B. Transmitted by arthropod vectors
• C. Respond to tetracycline therapy
• D. All of the above

Explanation: Rickettsiae are obligate intracellular bacteria, commonly spread by arthropods such as ticks, lice and mites, and are generally…

• A. Yaws
• B. Lepromatous Leprosy
• C. Malaria
• D. All of the above

Explanation: VDRL detects reagin antibodies, which may occur in infections or conditions other than syphilis, including yaws, lepromatous leprosy and…

• A. Tellurite Medium
• B. Cary Blair Medium
• C. Venkatraman - Ramakrishnan Medium
• D. B & C

Explanation: Cary-Blair medium is a standard transport medium for stool specimens containing Vibrio cholerae, while Venkatraman-Ramakrishnan medium is…

• A. Bacteroides fragilis
• B. Fusobacterium nucleatum
• C. Peptostreptococcus anaerobius
• D. Actinomyces Israeli
• E. All of the above

Explanation: Bacteroides fragilis, Fusobacterium nucleatum, Peptostreptococcus anaerobius and Actinomyces israelii are non-spore-forming anaerobic…

• A. Compliment fixation tests
• B. Pili agglutination tests
• C. Haemagglutination tests
• D. All of the above tests

Explanation: Older serological approaches to gonorrhoea included complement fixation, agglutination against gonococcal pili and haemagglutination…

• A. Streptococcus viridans
• B. Haemolytic streptococci
• C. Staphylococcus aureus
• D. Nisseria

Explanation: Subacute bacterial endocarditis classically affects previously abnormal valves and is most characteristically caused by the relatively…

• A. Tryptophan
• B. Niacin
• C. B-12
• D. Citrate

Explanation: Salmonella requires tryptophan as a growth factor in certain culture conditions.

• A. Neisseria gonorrhea
• B. Escherichia coli
• C. T-strain mycoplasma
• D. Streptococcus fecalis

Explanation: Escherichia coli is the commonest cause of urinary tract infections, especially uncomplicated community-acquired infections, because it is…

• A. Synapse
• B. Muscle
• C. Brain
• D. Spinal card

Explanation: Tetanospasmin blocks inhibitory neurotransmitter release from interneurons in the spinal cord, particularly glycine and GABA.