TNPSC Animal Husbandry & Veterinary Science (Degree Standard), Code 396 · India · Tamil Nadu Public Service Commission
Original practice questions written to the published syllabus · not past papersThe bacteria and fungi that cause disease in animals, genus by genus: what they are, where they live, what they cause and how they are identified.
In the exams: ICAR AICE-JRF core group 06; ICAR AIEEA-PG 13 (Microbiology); China preventive paper
How our questions for TNPSC Animal Husbandry & Veterinary Science, Code 396 spread across the units of Systematic Veterinary Bacteriology & Mycology. Difficulty: 22 easy, 12 medium, 1 hard.
| Aspergillus and Candida | 4 | |
| Bacillus anthracis | 3 | |
| Brucella | 3 | |
| Burkholderia mallei (glanders) | 3 | |
| Staphylococcus | 2 | |
| Streptococcus | 2 | |
| Mycobacterium: tuberculosis and Johne's disease | 2 | |
| Pasteurella and Mannheimia | 2 | |
| Salmonella | 2 | |
| Escherichia coli | 2 | |
| Leptospira | 2 | |
| Mycoplasma | 2 | |
| Rickettsia and Chlamydia | 2 | |
| Dermatophytes | 2 | |
| Clostridium | 1 | |
| Listeria | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Which single bench test most quickly separates a Gram-positive coccus isolated from mastitic milk into Staphylococcus or Streptococcus?
D. Catalase test: staphylococci bubble, streptococci do not
Staphylococci are catalase positive and release bubbles from hydrogen peroxide; streptococci are catalase negative. Coagulase is used after catalase, to split staphylococci into coagulase-positive and coagulase-negative groups, and streptococci do not clot plasma. Oxidase and indole are tests for Gram-negative rods.
Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease; WOAH Terrestrial Manual
Weaned pigs show paddling, opisthotonos and sudden death, and a pig farmer later develops meningitis with hearing loss. Which organism links the two?
C. Streptococcus suis serotype 2
S. suis, classically serotype 2, causes meningitis, arthritis and septicaemia in weaners and is a zoonosis of people handling pigs and pork, with meningitis and deafness. Glaesserella (Haemophilus) parasuis causes polyserositis and meningitis in pigs but is not a zoonosis; F18 E. coli causes oedema disease with neurological signs but not human meningitis.
Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease; WOAH Terrestrial Manual
A cow is found dead with dark, unclotted blood oozing from the nostrils and anus. What should the veterinarian do first?
C. Take a blood smear from an ear vein and keep the carcass unopened
The picture suggests anthrax. Opening the carcass exposes the bacilli to air, so they sporulate and contaminate the site for decades; the diagnosis is made from a peripheral blood smear stained by the M'Fadyean method. Moving the carcass spreads contamination; treating in-contacts may be part of control, but not with a necropsy afterwards.
Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease; WOAH Terrestrial Manual
Mycobacteria resist decolourisation by acid-alcohol in the Ziehl-Neelsen stain because their cell wall is rich in:
C. Mycolic acids
Long-chain mycolic acids make the wall waxy, so carbol fuchsin is retained after acid-alcohol and the bacilli stay red. Teichoic acids are features of ordinary Gram-positive walls, and lipopolysaccharide is the outer membrane of Gram-negative bacteria; neither confers acid-fastness.
Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease; WOAH Terrestrial Manual
Chicks under three weeks old die in large numbers with white, pasty diarrhoea, and the infection is traced to the breeder flock. The organism is:
B. Salmonella Pullorum
Pullorum disease (bacillary white diarrhoea) is caused by S. Pullorum, which is transmitted through the egg and kills young chicks. Breeder flocks are tested by plate agglutination and reactors removed. S. Typhimurium is not host-adapted and less often causes this pattern.
Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease; WOAH Terrestrial Manual
Leptospires are best seen alive in a fresh sample using:
C. Dark-field microscopy
Leptospires are very thin and stain poorly with Gram stain, so live organisms are seen as motile, coiled, hooked spirochaetes by dark-field microscopy; silver stains or immunohistochemistry are used in tissue. India ink shows the capsule of Cryptococcus.
Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease; WOAH Terrestrial Manual
Growing pigs fed mouldy maize develop poor growth, jaundice and bleeding, and dairy cows on the same farm have a toxin in their milk. Which mycotoxin is involved?
D. Aflatoxin, appearing in milk as aflatoxin M1
Aflatoxins from Aspergillus flavus and A. parasiticus are hepatotoxic, causing jaundice, poor growth and coagulopathy, and aflatoxin B1 is converted to M1, which is excreted in milk and is regulated by milk limits. Zearalenone is oestrogenic, deoxynivalenol causes feed refusal and vomiting, and ergot causes gangrene of the extremities; none of these is the classic cause of liver damage with a milk residue.
Further reading: Quinn et al., Veterinary Microbiology and Microbial Disease; WOAH Terrestrial Manual
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