How Much Do You Really Know About Microbiology?

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Quizzes Created: 37 | Total Attempts: 137,568
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  • 1/10 Questions

    A veterinary doctor had pyrexia of unknown origin. His blood culture in special laboratory media was positive for gram-negative short bacilli which was oxidase positive. Which one of the following is the likely organism grown in culture?

    • Pasteurella spp
    • Francisella spp
    • Bartonella spp
    • Brucella spp
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About This Quiz

There are different organisms on the earth and some we can see with a naked eye while others you cannot. Microbiology gives the student a chance to study microorganisms such as bacteria and viruses. The quiz below is designed to help you figure out how attentive you have been when it comes to microbiology class. Take it up and see just how well you will do!

How Much Do You Really Know About Microbiology? - Quiz

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  • 2. 

    Cholera toxin:

    • Increases the levels of intracellular cylic GMP

    • Acts through the opoid receptors

    • Causes continued activation of adenylate cyclase

    • Lnhibits the enzyme phosphodiesterase

    Correct Answer
    A. Causes continued activation of adenylate cyclase
    Explanation
    Cholera toxin causes continued activation of adenylate cyclase. Adenylate cyclase is an enzyme responsible for producing cyclic adenosine monophosphate (cAMP) from adenosine triphosphate (ATP). Increased levels of cAMP lead to the activation of protein kinase A, which in turn leads to the phosphorylation of various proteins and subsequent cellular responses. Therefore, cholera toxin's ability to cause continued activation of adenylate cyclase results in increased cAMP levels and subsequent cellular effects.

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  • 3. 

    A patient admitted to an ICU is on central venous line for the last one week. He is on ceftazidime and amikacin. After 7 days of antibiotics he develops a spike of fever an his blood culture is positive for gram positive cocci in chains, which are catalase negative. Following this, vancomycin was started but the culture remained positive for the same organism even after 2 weeks of therapy. The most likely organism causing infection is:

    • Staphylococcus aureus

    • Viridans streptococci

    • Enterococcus faecalis

    • Coagulase negative Staphylococcus

    Correct Answer
    A. Enterococcus faecalis
    Explanation
    The most likely organism causing the infection is Enterococcus faecalis. This is indicated by the fact that the patient developed a fever and the blood culture was positive for gram positive cocci in chains, which are catalase negative. Enterococcus faecalis is a gram positive cocci that often forms chains and is catalase negative. Additionally, the fact that the culture remained positive for the same organism even after 2 weeks of therapy with vancomycin suggests that the organism is resistant to this antibiotic, which is a characteristic of Enterococcus faecalis.

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  • 4. 

    A child had pustular lesion on leg. On gram staining gram positive cocci are seen. To establish the diagnosis of Group A streptococcal erythroderma, the test used is

    • Bile solubility test

    • Catalase test

    • Optochin sensitivity

    • Bacitracin sensitivity

    Correct Answer
    A. Bacitracin sensitivity
    Explanation
    The correct answer is Bacitracin sensitivity. This test is used to establish the diagnosis of Group A streptococcal erythroderma. Group A streptococci are sensitive to bacitracin, so if the bacteria are inhibited by bacitracin, it suggests that the infection is caused by Group A streptococci. The other tests listed, such as bile solubility, catalase, and optochin sensitivity, are not specific for Group A streptococci and are used for different purposes.

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  • 5. 

    ln the gut, anaerobic bacteria outnumber the aerobes by a ratio of

    • 10:1

    • 100:1

    • 1000:1

    • 10,000:1

    Correct Answer
    A. 1000:1
    Explanation
    In the gut, there is a higher population of anaerobic bacteria compared to aerobes. This is supported by the fact that the ratio of anaerobic bacteria to aerobes is 1000:1. This means that for every 1 aerobe, there are 1000 anaerobic bacteria present in the gut.

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  • 6. 

    With reference to Bacteroides fragilis the following statements are true except-

    • B. fragilis is the most frequent anaerobe isolated from clinical samples.

    • B. fragilis is not uniformly sensitive to metronidazole

    • The lipopolysaccharide formed by B. fragilis is structurally and functionally different from the conventional endotoxin

    • Shock and disseminated intravascular coagulation are common in Bacteriodes bacteremia

    Correct Answer
    A. Shock and disseminated intravascular coagulation are common in Bacteriodes bacteremia
    Explanation
    Bacteroides:

    Gram negative anaerobic bacilli
    Most common anaerobic pathogen isolated from clinical specimens
    Virulence factors include capsular polysaccharides and lipopolysaccharide endotoxin
    Lipopolysaccharide endotoxin is much less toxic compared to other gram negative bacteria
    Hence infections do not directly produce signs of sepsis, which is common in other gram negative bacteria
    Some are resistant to metronidazole

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  • 7. 

    A young boy had a flea bite while working in a wheat grain godown. After 5 days he developed fever and had axillary lymphadenopathy. A smear was sent to the laboratory to perform a specific staining. Which one of the following staining method would help in the identification of the suspected pathogen:

    • Albert staining

    • Ziehl Neelsen staining

    • McFadyen’s staining

    • Wayson staining

    Correct Answer
    A. Wayson staining
    Explanation
    Flea bite might have been by a rat flea as wheat grain godowns are frequented by rats. Fever and axillary lymphadenopathy are characteristic features of bubonic plague – which is spread by bite of rat flea. Wayson stain is used to demonstrate Yersinia pestis which is the causative organism for plague.

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  • 8. 

    An infant had high grade fever and respiratory distress at the time of presentation to the emergency room. The sample collected for blood culture was subsequently positive showing growth of a haemolytic colonies. On Gram staining these were gram positive cocci. In the screening test for identification, the suspected pathogen is likely to be susceptible to the following agent:

    • Bacitracin

    • Novobiocin

    • Optochin

    • Oxacillin

    Correct Answer
    A. Optochin
    Explanation
    Optochin is likely to be the susceptible agent for the suspected pathogen. This is because the question mentions that the Gram staining showed gram positive cocci, and optochin is a screening test used to identify Streptococcus pneumoniae, which is a common gram positive cocci pathogen. Optochin sensitivity is a characteristic feature of Streptococcus pneumoniae, making it the correct answer in this case.

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  • 9. 

    Which one of the following statement is true regarding pathogenicity of Mycobacteria species?

    • M. tuberculosis is more pathogenic than M. bovis to humans

    • M. Kansasii can cause a disease indistinguishable from tuberculosis

    • M Africanum infection is acquired from an environmental source

    • M. Marinum is responsible for tubercular lymphadenopathy

    Correct Answer
    A. M. Kansasii can cause a disease indistinguishable from tuberculosis
    Explanation
    M. tuberculosis and M. bovis are equally pathogenic to humans. M Africanum is part of M. tuberculosis complex together with M.tuberculosis, M.bovis and M.microti. Environmental sources are present in case of non tuberculous mycobacteria and atypical mycobacteria. They are not seen in case of bacteria belonging to M.tuberculosis complex.

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  • 10. 

    A VDRL reactive mother gave birth to an infant. All of the following would help in determining the risk of transmission to the infant except:

    • TPHA test on the serum sample of the mother

    • TPHA test on the serum sample of the infant

    • VDRL on the paired serum sample of the infant and mother

    • Time interval between the treatment of the mother and her delivery

    Correct Answer
    A. TPHA test on the serum sample of the infant
    Explanation
    Serological testing for syphilis is not reliable in case of neonates. Negative serology does not rule out the possibility of infection.

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  • Current Version
  • Mar 20, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Jul 18, 2011
    Quiz Created by
    Pgblazer
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