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National Practising Veterinarian Qualification Examination General Veterinary Microbiology: practice questions

National Practising Veterinarian Qualification Examination (全国执业兽医资格考试) · China · Examination committee under the Ministry of Agriculture and Rural Affairs (MARA)

Original practice questions written to the published syllabus · not past papers
10worked here, free
42written to this exam in this subject
10syllabus units

What this subject covers

How bacteria and fungi are built, grown, identified and killed, and how bacteria become resistant to antimicrobials.

In the exams: ICAR AICE-JRF core group 06; ICAR AIEEA-PG 13 (Microbiology); PRC Microbiology & Public Health 14%; China microbiology and immunology 35 (its largest single component); TNPSC Micro/VPH/Preventive Medicine 30

What National Practising Veterinarian Qualification Examination asks from it

China National Practising Veterinarian Qualification Examination — microbiology and immunology

Bacterial structure and special structures, growth conditions and the growth curve, sterilisation and disinfection terms and methods, variation and gene transfer, pathogenicity (toxins, invasiveness), and the principles of bacterial and fungal laboratory diagnosis.

Where the 42 questions fall

How our questions for National Practising Veterinarian Qualification Examination spread across the units of General Veterinary Microbiology. Difficulty: 21 easy, 20 medium, 1 hard.

General mycology7
Culture methods5
Bacterial identification5
Disinfection5
Bacterial structure4
Bacterial growth4
Bacterial genetics4
Bacterial classification3
Sterilisation3
Mechanisms of antimicrobial resistance2

10 practice questions, worked

Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.

1 · Bacterial classification · easy

Taxonomy, as used in bacteriology, comprises:

  1. Staining, culture and serology
  2. Mutation, recombination and selection
  3. Classification, nomenclature and identification
  4. Isolation, identification and susceptibility testing
Answer and working

C. Classification, nomenclature and identification

Taxonomy is the science of arranging organisms into groups (classification), naming them (nomenclature) and assigning an unknown isolate to a named group (identification). The other lists are laboratory or genetic processes.

Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease, 2nd ed.

2 · Bacterial classification · medium

In the name 'Salmonella enterica subsp. enterica serovar Typhimurium', the word Typhimurium denotes:

  1. A subspecies of Salmonella bongori
  2. A serovar, defined by its O and H antigens
  3. A separate species of Salmonella
  4. A biovar defined by carbohydrate fermentation
Answer and working

B. A serovar, defined by its O and H antigens

The genus Salmonella has two species, S. enterica and S. bongori. Most animal and human pathogens belong to S. enterica subsp. enterica and are divided into serovars. A serovar name is written with a capital letter and is not italicised, which is why 'Salmonella typhimurium' as a species name is outdated.

Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease, 2nd ed.

3 · Bacterial growth · easy

The correct order of the phases of a bacterial growth curve in a closed (batch) culture is:

  1. Lag, stationary, exponential, death
  2. Lag, exponential, stationary, death
  3. Exponential, lag, stationary, death
  4. Stationary, lag, exponential, death
Answer and working

B. Lag, exponential, stationary, death

Inoculated cells first adapt (lag), then divide at a constant rate (exponential), then growth equals death as nutrients run out and wastes build up (stationary), and finally viable numbers fall (death or decline).

Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease, 2nd ed.

4 · Culture methods · easy

On MacConkey agar, lactose-fermenting colonies such as Escherichia coli appear pink to red because:

  1. Crystal violet is reduced by the colonies
  2. Bile salts react with lactose to form a red pigment that diffuses into the colony
  3. Acid from lactose fermentation turns the neutral red indicator red
  4. The colonies produce hydrogen sulphide
Answer and working

C. Acid from lactose fermentation turns the neutral red indicator red

MacConkey agar is selective (bile salts and crystal violet inhibit most Gram-positive bacteria) and differential (lactose with neutral red). Fermenters lower the pH and turn pink-red; non-fermenters such as Salmonella and Proteus stay pale.

Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease, 2nd ed.

5 · Culture methods · hard

When collecting quarter milk samples for mastitis culture, the recommended order is to:

  1. Disinfect the near teats first and sample the far teats first
  2. Disinfect teat ends from the far teats, then sample starting with the near teats
  3. Sample all teats first, then disinfect them with a teat dip so the milk is not contaminated by the dip
  4. Collect the first streams of milk into the sample tube
Answer and working

B. Disinfect teat ends from the far teats, then sample starting with the near teats

Scrubbing far teats first and sampling near teats first avoids reaching across, and contaminating, teats already cleaned. Foremilk is discarded, not sampled, and teat ends are scrubbed with 70% alcohol until the swab is clean.

Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease, 2nd ed.

6 · Bacterial genetics · easy

The uptake of free (naked) DNA from the environment by a competent bacterial cell is called:

  1. Transposition
  2. Transduction
  3. Conjugation
  4. Transformation
Answer and working

D. Transformation

Transformation = free DNA; transduction = DNA carried by a bacteriophage; conjugation = transfer through direct cell contact, usually via a sex pilus. Griffith's experiment with pneumococci first demonstrated transformation.

Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease, 2nd ed.

7 · Sterilisation · medium

Ethylene oxide is used to sterilise heat-sensitive instruments such as some plastic endoscopes. Its main practical drawback is that:

  1. It requires temperatures above 160 degrees C, which melt most plastic endoscopes
  2. It is toxic and carcinogenic, so items need a long aeration period to remove residues
  3. It only works on metal instruments
  4. It cannot kill bacterial spores, so it is rated only as a high-level disinfectant and not a sterilant
Answer and working

B. It is toxic and carcinogenic, so items need a long aeration period to remove residues

Ethylene oxide is an alkylating agent that kills spores at low temperature (about 37-63 degrees C) and penetrates packaging, but it is flammable, toxic and carcinogenic. Items must be aerated before use.

Further reading: Rutala, Weber and HICPAC, CDC Guideline for Disinfection and Sterilization in Healthcare Facilities

8 · Disinfection · medium

Ethyl alcohol is a more effective disinfectant at about 70% than at 100% because:

  1. Water converts ethanol into formaldehyde, which is the active killing agent
  2. Water is needed for protein denaturation and slows evaporation, prolonging contact time
  3. Absolute alcohol kills spores too quickly
  4. 70% alcohol is a sterilant while 100% is not, because it penetrates spore coats more deeply
Answer and working

B. Water is needed for protein denaturation and slows evaporation, prolonging contact time

Alcohols act by denaturing proteins and dissolving lipids, which proceeds poorly without water. Neither concentration is sporicidal, so alcohol is not a sterilant.

Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease, 2nd ed.

9 · Mechanisms of antimicrobial resistance · easy

Beta-lactam antibiotics such as penicillins and cephalosporins act by:

  1. Blocking dihydrofolate reductase
  2. Inhibiting DNA gyrase
  3. Binding the 30S ribosomal subunit and causing misreading of mRNA during protein synthesis
  4. Binding penicillin-binding proteins and blocking peptidoglycan cross-linking
Answer and working

D. Binding penicillin-binding proteins and blocking peptidoglycan cross-linking

Penicillin-binding proteins are the transpeptidases that cross-link peptidoglycan. The 30S target belongs to aminoglycosides and tetracyclines, DNA gyrase to fluoroquinolones, and dihydrofolate reductase to trimethoprim.

Further reading: CLSI VET01/VET01S; WOAH Terrestrial Manual ch. 2.1.1; Giguere et al., Antimicrobial Therapy in Veterinary Medicine, 5th ed.

10 · General mycology · easy

Brooder pneumonia, with yellowish nodules in the lungs and air sacs of young chicks, is caused mainly by:

  1. Microsporum gallinae
  2. Cryptococcus neoformans
  3. Candida albicans
  4. Aspergillus fumigatus
Answer and working

D. Aspergillus fumigatus

Chicks inhale large numbers of A. fumigatus conidia from mouldy litter or contaminated hatcheries. Candida albicans causes crop mycosis ('thrush'), and Microsporum gallinae (now Lophophyton gallinae) causes favus of the comb.

Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease, 2nd ed.

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Read the subject

General Veterinary MicrobiologyThe full study manual, free National Practising Veterinarian Qualification ExaminationFormat, sections and how it has changed

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General Veterinary Microbiology for other exams

ASRB NET and ARS / SMS / STO · IndiaICAR AIEEA · IndiaRPSC Veterinary Officer · IndiaTNPSC Animal Husbandry & Veterinary Science, Code 396 · IndiaVeterinarian National Examination · South KoreaNational Licensure Examination for Veterinarians · NepalVeterinarian Licensure Examination · PhilippinesAustralasian Veterinary Examination, formerly the National Veterinary Examination · Australia / New ZealandBCSE · USA / CanadaNAVLE · USA / CanadaRCVS Statutory Membership Examination · UKSAVC Registration Examination · South Africa

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