General microbiology: history, scope and laboratory safety

17 Kerala PSC Lab Technician Gr II practice questions on General microbiology: history, scope and laboratory safety, part of Microbiology. The first 17 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Easy

   Who introduced carbolic acid (phenol) to prevent wound infection after surgery?

   1. AIgnaz Semmelweis
   2. BRobert Koch
   3. CLouis Pasteur
   4. DJoseph Lister

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   Answer: D · Joseph Lister

   Joseph Lister, building on Pasteur's germ theory, began applying carbolic acid to wounds, dressings and instruments in the 1860s. Infection and deaths after surgery fell sharply, and he is remembered as the father of antiseptic surgery. Phenol later became the reference disinfectant against which others are compared in the Rideal-Walker test.

   • A: Semmelweis reduced puerperal fever with chlorinated lime hand washing, not carbolic acid.
   • B: Koch discovered the tubercle bacillus and set out his postulates.
   • C: Pasteur proved the germ theory and developed vaccines; he did not introduce surgical antisepsis.

2. Question 2 · Easy

   Which class of biological safety cabinet is gas-tight and is worked only through attached rubber gloves?

   1. AClass II A2
   2. BClass II B2
   3. CClass I
   4. DClass III

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   Answer: D · Class III

   A Class III cabinet is a fully enclosed, gas-tight box kept under negative pressure, and material is handled only through glove ports. Supply air enters through a HEPA filter, and exhaust air passes through two HEPA filters or a HEPA filter and an incinerator. It gives the highest protection and is used for risk group 4 agents. Class I and Class II cabinets have an open front through which the worker reaches in.

   • A: A Class II A2 cabinet has an open front protected by an inflow air curtain.
   • B: A Class II B2 cabinet is fully exhausted but still has an open front.
   • C: A Class I cabinet has an open front and protects the worker but not the material.

3. Question 3 · Medium

   Koch's postulates cannot be fulfilled for which bacterium, because it has never been grown on artificial media?

   1. AMycobacterium leprae
   2. BVibrio cholerae
   3. CMycobacterium tuberculosis
   4. DBacillus anthracis

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   Answer: A · Mycobacterium leprae

   Koch's postulates require the organism to be grown in pure culture and to reproduce the disease when inoculated into a susceptible animal. Mycobacterium leprae has never been cultured on artificial media; it is grown only in the mouse footpad or the nine-banded armadillo. Treponema pallidum is a similar exception. Koch himself worked out the postulates with the anthrax bacillus and the tubercle bacillus.

   • B: V. cholerae grows well on ordinary and alkaline media such as TCBS agar.
   • C: M. tuberculosis grows on Lowenstein-Jensen medium and was isolated by Koch in 1882.
   • D: B. anthracis grows readily on ordinary media and was Koch's first model organism.

4. Question 4 · Medium

   A technician pricks a finger with a needle used on an HIV-positive patient. After washing the wound, when should post-exposure prophylaxis begin?

   1. AOnly if the wound continues to bleed
   2. BAs soon as possible, ideally within 2 hours
   3. CWithin 7 days, after a baseline HIV test
   4. DOnly after the source's viral load is known

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   Answer: B · As soon as possible, ideally within 2 hours

   NACO guidelines advise starting post-exposure prophylaxis as early as possible, ideally within 2 hours, and not later than 72 hours after the exposure. First aid is washing the site with soap and running water, without scrubbing or squeezing the wound. A baseline HIV test is taken, but treatment is not delayed for its result. The drugs are taken for 28 days, and the injury is reported and recorded.

   • A: A needle-stick with blood from an HIV-positive patient needs PEP whether or not it bleeds.
   • C: PEP is of little value after 72 hours, and the baseline test must not delay it.
   • D: Waiting for the source's viral load delays a treatment that works best when started early.

5. Question 5 · Medium

   In Pasteur's swan-neck flask experiment, boiled broth stayed clear although air could enter the flask. Why?

   1. ANo oxygen could reach the broth
   2. BBoiling made the broth antimicrobial
   3. CBoiling removed the broth's nutrients
   4. DMicrobes settled in the curved neck

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   Answer: D · Microbes settled in the curved neck

   The long S-shaped neck let air in freely, but dust particles carrying microbes were trapped in its moist bend. The broth stayed clear for months, yet became cloudy soon after the neck was broken off or the broth was tipped into the bend. This showed that microbes arise from microbes already present in the air, and it disproved spontaneous generation.

   • A: Air, including oxygen, entered freely through the open neck.
   • B: The same broth became turbid once it touched the dust in the bend.
   • C: The broth grew microbes as soon as the neck was broken, so its nutrients were intact.

6. Question 6 · Hard

   During centrifugation of sputum samples, a technician hears glass breaking inside the closed centrifuge. The buckets are not sealed. What should be done first?

   1. AOpen the lid and spray alcohol into the bowl
   2. BSwitch off and keep the lid shut for 30 minutes
   3. COpen the lid at once and remove the broken tube
   4. DLet the run finish, then disinfect the buckets

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7. Question 7 · Easy

   Agar was first used to solidify bacterial culture media in Koch's laboratory on the suggestion of:

   1. APaul Ehrlich
   2. BHans Christian Gram
   3. CJulius Petri
   4. DFanny Hesse

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8. Question 8 · Easy

   Who first described bacteria, which he called "animalcules", using simple microscopes of his own making?

   1. ARobert Koch
   2. BRobert Hooke
   3. CLouis Pasteur
   4. DAntonie van Leeuwenhoek

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9. Question 9 · Easy

   Growing and handling cultures of Mycobacterium tuberculosis is classically done at which biosafety level?

   1. ABSL-3
   2. BBSL-2
   3. CBSL-1
   4. DBSL-4

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10. Question 10 · Medium

    A flask of broth culture breaks on the bench. After the spill is covered with paper towels, the disinfectant should be poured:

    1. AOnly onto the middle of the spill
    2. BFrom the edges towards the centre
    3. CFrom the centre towards the edges
    4. DOnly after the towels are removed

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11. Question 11 · Medium

    Why is the blower of a Class II biological safety cabinet run for about 5 minutes before work begins?

    1. ATo let the UV lamp disinfect the surface
    2. BTo warm the HEPA filters to working temperature
    3. CTo dry the disinfectant on the work surface
    4. DTo purge the air and settle the airflow

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12. Question 12 · Hard

    A technician fully vaccinated against hepatitis B, whose anti-HBs was 120 mIU/mL after the course, has a needle-stick injury from an HBsAg-positive sample. After washing the site, what hepatitis B prophylaxis does he need?

    1. AA fresh three-dose vaccine series
    2. BNone; he is a known responder
    3. CHBIG plus one vaccine booster dose
    4. DTwo doses of HBIG one month apart

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13. Question 13 · Medium

    Why is a Class I biological safety cabinet unsuitable when the culture itself must be kept free of contamination?

    1. AIts exhaust air is not HEPA-filtered
    2. BIt has no front opening for the arms
    3. CUnfiltered room air sweeps over the work
    4. DIts airflow blows towards the worker

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14. Question 14 · Medium

    Pasteur called his attenuated preparations "vaccines" to honour:

    1. AIgnaz Semmelweis's handwashing
    2. BEdward Jenner's cowpox work
    3. CJoseph Lister's antisepsis
    4. DRobert Koch's postulates

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15. Question 15 · Hard

    A technician must process 20 sputum samples for AFB culture: NaOH decontamination, vortex mixing and centrifugation. Which set-up is safest?

    1. AClass II cabinet with its UV lamp on during work
    2. BOpen bench near a Bunsen flame; surgical mask
    3. CLaminar-flow clean bench; N95 respirator
    4. DClass II cabinet; sealed buckets opened inside it

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16. Question 16 · Easy

    Routine diagnostic work on blood and serum samples, which may carry HBV or HIV, is normally done at which biosafety level?

    1. ABSL-1
    2. BBSL-4
    3. CBSL-3
    4. DBSL-2

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17. Question 17 · Easy

    Robert Koch identified the causative bacterium of:

    1. AWhooping cough
    2. BTuberculosis
    3. CPlague
    4. DDiphtheria

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