Q20. What is a bacteriophage?
[WBCS Prelims 2017]
- (A) A virus that infects bacteria
- (B) A bacterium grown on agar
- (C) A fungus that causes illness
- (D) A protozoan that engulfs bacteria
Answer: (A) A virus that infects bacteria
Explanation: A bacteriophage is a virus that infects bacterial cells, sometimes destroying them through a lytic cycle. Because phages can target bacteria, researchers investigate their possible roles in treating certain antibiotic-resistant infections, although clinical applications require careful evaluation.
Q19. Which of the following diseases is caused by a protozoan rather than a bacterium?
[MPPSC State Service Prelims 2017, General Science]
- (A) Cholera
- (B) Diphtheria
- (C) Pneumonia
- (D) Malaria
Answer: (D) Malaria
Explanation: Malaria is caused by protozoan parasites belonging to Plasmodium. Cholera is caused by Vibrio cholerae, diphtheria by Corynebacterium diphtheriae, and bacterial pneumonia may be caused by Streptococcus pneumoniae. The question tests recognition of distinct infectious agents.
Q18. Which pairing is incorrect?
[UP Review Officer/Assistant Review Officer Prelims 2016]
- (A) Autoimmune disorder — rheumatoid arthritis
- (B) Genetic disorder — tuberculosis
- (C) Scabies — mite
- (D) Mental disorder — schizophrenia
Answer: (B) Genetic disorder — tuberculosis
Explanation: Tuberculosis is an acquired infectious disease caused by Mycobacterium tuberculosis, not a genetic disorder. Rheumatoid arthritis is autoimmune; scabies results from a parasitic mite infestation; and schizophrenia is a psychiatric illness. The question contrasts distinct categories of disease.
Q17. Which illness is commonly transmitted by contaminated water?
[UPPSC PCS Prelims, 10 May 2015]
- (A) Smallpox
- (B) Malaria
- (C) Cholera
- (D) Pulmonary tuberculosis
Answer: (C) Cholera
Explanation: Cholera spreads mainly through food or water contaminated with Vibrio cholerae. Smallpox was a viral infection spread principally through close contact; malaria is mosquito-borne; and pulmonary tuberculosis is airborne. Water safety and sanitation are essential for cholera prevention.
Q16. Which classical skin test is associated with detecting immune sensitisation to tuberculosis?
[UP Lower Subordinate Mains 2015]
- (A) Robert’s test
- (B) Widal test
- (C) Kahn test
- (D) Mantoux test
Answer: (D) Mantoux test
Explanation: The Mantoux tuberculin skin test checks delayed-type immune reactivity to tuberculosis antigens. It indicates TB infection or sensitisation, not necessarily active disease. Further clinical assessment and microbiological testing are needed before diagnosing active tuberculosis.
Q15. Of diphtheria, chickenpox and smallpox, which had been eradicated in India by 2014?
[UPSC Civil Services Prelims 2014]
- (A) Diphtheria and chickenpox only
- (B) Smallpox only
- (C) All three
- (D) None
Answer: (B) Smallpox only
Explanation: Smallpox, caused by variola virus, was eradicated globally in 1980 after intensive vaccination and surveillance. Diphtheria is bacterial and remains vaccine-preventable but not eradicated. Chickenpox is a viral infection and has not been globally eradicated.
Q14. Botulism is linked to which bacterial genus?
[UP Lower Subordinate Prelims 2013]
- (A) Azotobacter
- (B) Lactobacillus
- (C) Clostridium
- (D) Rhizobium
Answer: (C) Clostridium
Explanation: Botulism is caused by botulinum neurotoxin, produced mainly by Clostridium botulinum and certain related clostridia. This potent toxin blocks acetylcholine release, causing descending flaccid paralysis. Safe food handling and correct preservation reduce foodborne botulism risk.
Q13. The letters DPT refer to vaccines against which group?
[UPPSC PCS Mains 2013]
- (A) Tetanus, polio, plague
- (B) TB, polio, diphtheria
- (C) Diphtheria, pertussis, tetanus
- (D) Diphtheria, polio, leprosy
Answer: (C) Diphtheria, pertussis, tetanus
Explanation: DPT vaccination protects against three bacterial diseases: diphtheria, pertussis and tetanus. Protection against diphtheria and tetanus principally targets bacterial toxins, while pertussis components protect against Bordetella pertussis infection and its serious consequences.
Q12. The disease tuberculosis is caused by which kind of pathogen?
[CGPSC State Service Prelims 2012 cycle (held 9 July 2013), Q26]
- (A) Virus
- (B) Bacterium
- (C) Fungus
- (D) Protozoan
Answer: (B) Bacterium
Explanation: Tuberculosis is caused principally by Mycobacterium tuberculosis, a slow-growing bacterial pathogen. Pulmonary disease spreads through infectious airborne particles. Common features include prolonged cough, fever, night sweats and weight loss; diagnosis and complete multidrug treatment are important.
Q11. Match the organisms causing plague, AIDS, fungal scalp disease and malaria to their categories.
[UPPSC PCS Prelims 2012]
- (A) Bacterium, virus, fungus, protozoan
- (B) Virus, bacterium, protozoan, fungus
- (C) Protozoan, fungus, virus, bacterium
- (D) Fungus, protozoan, bacterium, virus
Answer: (A) Bacterium, virus, fungus, protozoan
Explanation: Plague is bacterial, AIDS is caused by HIV, many scalp fungal infections arise from dermatophytes, and malaria is protozoan. This comparison is important because treatment and transmission patterns differ sharply among bacteria, viruses, fungi and protozoa.
