All Free Microbiology MCQs with Answers

• A. Clostridium tetani travels via the nerves to the anterior horn dells in spinal cord
• B. The tetanospasmin component of the exotoxin act on the post-synaptic neurones and prevents impulse transmission
• C. The patient should be given tetanus toxoid intravenously
• D. Causes positive Nagler reaction

Explanation: Tetanospasmin travels by retrograde axonal transport to the spinal cord, where it blocks inhibitory interneuron function and causes muscle…

• A. Produces heat stable enterotoxin
• B. Causes Shangai fever
• C. Cannot be destroyed at 55 degree at 1 hr.
• D. Does not produce any pigment

Explanation: Pseudomonas aeruginosa can cause Shanghai fever, an enteric illness especially described in children.

• A. It is non-halophilic
• B. Grows on simple media
• C. Man is the only natural host
• D. Cannot survive in extracellular environment

Explanation: Vibrio cholerae is non-halophilic, grows on ordinary media, and has humans as its main natural host.

• A. Susceptible to many antibiotics
• B. Present mainly in mixed infections
• C. Most common species is B fragilis
• D. Bile resistant anerobes

Explanation: Bacteroides, particularly Bacteroides fragilis, are commonly found in mixed anaerobic infections and are bile resistant.

• A. Most common cause of urethritis is male
• B. All stains are highly susceptible to penicillin
• C. Wide spread axoregnic stains cause disseminated gonococcal infection
• D. Found exclusively in human beings.

Explanation: Penicillin resistance is common among Neisseria gonorrhoeae strains because of beta-lactamase production and altered penicillin-binding…

• A. Dextran
• B. Epithelial cells
• C. Bacteria
• D. Sucrose

Explanation: Streptococcal plaque bacteria produce dextran from dietary sucrose, and this sticky polysaccharide helps the plaque adhere to the tooth…

• A. Gram's stain
• B. H & E stain
• C. Ziehl-Neelsen stain
• D. PAS stain

Explanation: Mycobacterium tuberculosis has a lipid-rich, waxy cell wall that resists ordinary staining and is demonstrated by the acid-fast…

• A. Treponema pallidum
• B. Treponjema pertenue
• C. Borrelia burgdorferi
• D. Borrelia vincenti

Explanation: Fusospirochetosis, classically associated with Vincent infection, involves Borrelia vincenti together with fusiform bacilli.

• A. Streptococcus sanguis
• B. Porphyromonas gingivalis
• C. Treponema denticola
• D. Spirochetes

Explanation: Streptococcus sanguis, now commonly called Streptococcus sanguinis, is part of the relatively harmless early oral flora and may help limit…

• A. H. influenza
• B. Moraxella catarrhalis
• C. Legionella
• D. Burkholderia cepacia

Explanation: Legionella requires the enriched charcoal yeast extract medium, often supplemented with cysteine and iron, for growth.

• A. Shigella sonnei
• B. Salmonella typhi
• C. Proteus mirabilis
• D. Klebsiella pneumonia

Explanation: Shigella sonnei is nonmotile and does not produce gas from glucose, making it anaerogenic.

• A. Chlamydia trachomatis
• B. Donovania granulomatis
• C. Bartonella henselae
• D. Hemophilia ducreya

Explanation: Bartonella henselae is transmitted mainly by scratches or bites from cats, especially kittens, and causes regional lymphadenopathy.

• A. Pseudomonas aerogenosa
• B. coli
• C. Proteus
• D. diphtheria

Explanation: Pseudomonas aeruginosa is an obligate aerobe and uses oxygen for its respiratory metabolism.

• A. Enterotoxin A
• B. Enterotoxin B
• C. Enterotoxin D
• D. Enterotoxin F

Explanation: Staphylococcal toxic shock syndrome is caused by TSST-1, historically called staphylococcal enterotoxin F.

• A. Staph. aureus
• B. Salmonella
• C. B.Cereus
• D. Clostridium botulinum

Explanation: Vomiting and abdominal symptoms within about 6 hours of eating contaminated milk products point to preformed Staphylococcus aureus…

• A. Transduction
• B. Translation
• C. Cell fusion
• D. Conjugation

Explanation: Among the listed bacterial gene-transfer mechanisms, conjugation is the direct transfer of DNA from one living bacterial cell to another…

• A. E.coli
• B. Haemophilus
• C. Proteus
• D. Staphylococcus

Explanation: The Weil-Felix test detects antibodies against Proteus strains OX19, OX2 and OXK because these antigens cross-react with rickettsial…

• A. Vancomycin
• B. Imipenem
• C. Teichoplanin
• D. Linezolid

Explanation: MRSA should be treated with agents active against resistant Gram-positive cocci, such as vancomycin, teicoplanin or linezolid.

• A. Wilson Blair medium
• B. Bile broth
• C. Bordet Gengou medium
• D. Robertson cooked meat medium

Explanation: Bordetella pertussis is classically isolated on Bordet-Gengou medium, often supplemented with blood or replaced by charcoal-based…

• A. Gram positive bacteria
• B. Gram negative bacteria
• C. Yeast
• D. Protozoa

Explanation: Teichoic acids are characteristic polymers of Gram-positive cell walls, where they contribute to wall structure and surface charge.