Medical Microbiology Q&A Guide – 36 MCQs | Kenya MBChB

36 Year 2: Parasitology exam questions on Medical Microbiology Q&A Guide for medical students. Includes MCQs, answers, explanations and written questions. S

This MCQ set contains 36 questions on Medical Microbiology Q&A Guide in the Year 2: Parasitology unit. Each question includes the correct answer and a detailed explanation for active recall and exam preparation.

Q1: What kinds of roaches might you expect to encounter in Athens? A) German roaches

  1. A. American roaches
  2. B. Smokey brown roaches
  3. C. All of the above
  4. D. None of the above Answer: D) All of the above

Correct answer: A – American roaches

Athens, with its Mediterranean climate and urban environment, supports multiple cockroach species including German roaches (most common indoor species), American roaches (prefer warm, moist areas), and Smokey brown roaches (outdoor species that enter buildings). ---

Q2: What is the main advantage of using larval control against mosquitoes? A) Control will supplement natural control

  1. A. Larvae are restricted to confined aquatic habitats that can be treated
  2. B. Larval habitats do not support sensitive other organisms
  3. C. All of the above
  4. D. None of the above Answer: B) Larvae are restricted to confined aquatic habitats that can be treated

Correct answer: A – Larvae are restricted to confined aquatic habitats that can be treated

Larval control is advantageous because mosquito larvae are confined to specific aquatic breeding sites (pools, containers, marshes) making them easier to target with larvicides or environmental management compared to flying adult mosquitoes that are widely dispersed. ---

Q3: If you found lice eggs (nits) in someone's clothing, what species would they most likely be from? A) Crab lice (Pthirus pubis)

  1. A. Head lice (Pediculus capitis)
  2. B. Body lice (Pediculus humanus)
  3. C. Hog lice
  4. D. All of the above Answer: C) Body lice (Pediculus humanus)

Correct answer: A – Head lice (Pediculus capitis)

Body lice (Pediculus humanus corporis) are the only lice species that lay their eggs (nits) on clothing fibers, particularly along seams of garments. Head lice attach nits to hair shafts, while crab lice attach to coarse body hair. ---

Q4: What are effective non-pesticide ways to control problems from cockroaches? A) Store food in plastic containers

  1. A. Clean your kitchen counter tops nightly
  2. B. Seal up cracks and seams around pipes and cabinets
  3. C. All of the above
  4. D. A and C Answer: D) All of the above

Correct answer: A – Clean your kitchen counter tops nightly

Integrated pest management for cockroaches includes removing food sources (sealed containers), eliminating food residues (cleaning), and blocking entry points (sealing cracks). All these methods work together to make environments less suitable for cockroach survival and reproduction. ---

Q5: The pupal stage is found in: A) Incomplete metamorphosis

  1. A. Complete metamorphosis
  2. B. Both incomplete and complete metamorphosis
  3. C. Neither incomplete nor complete metamorphosis
  4. D. None of the above Answer: B) Complete metamorphosis

Correct answer: A – Complete metamorphosis

The pupal stage only occurs in complete metamorphosis (holometabolism) where insects go through egg → larva → pupa → adult stages. Incomplete metamorphosis (hemimetabolism) has only egg → nymph → adult stages with no pupal stage. ---

Q6: How does insecticide resistance develop? A) By using Integrated Pest Management practices

  1. A. By using low doses of insecticides
  2. B. By using high or prolonged doses of insecticide
  3. C. B and C
  4. D. None of the above Answer: D) B and C

Correct answer: A – By using low doses of insecticides

Insecticide resistance develops through both low doses (sub-lethal doses allow resistant individuals to survive and reproduce) and high/prolonged doses (intense selection pressure favors resistant genotypes). IPM actually helps prevent resistance by reducing selection pressure. ---

Q7: Ceratopogonidae larvae are found in: A) Freshwater marshes

  1. A. Salt marshes
  2. B. Wet muddy areas around cattle watering tanks
  3. C. All of the above
  4. D. A and B Answer: D) All of the above

Correct answer: A – Salt marshes

Ceratopogonidae (biting midges/no-see-ums) larvae are semi-aquatic and found in various moist environments including freshwater marshes, salt marshes, and muddy areas around water sources. Different species adapt to different salinity and moisture conditions. ---

Q8: Integrated Pest Management: A) Relies solely on pesticides

  1. A. Relies solely on biological and natural control
  2. B. Considers the biology of the target pest
  3. C. A and B
  4. D. All of the above Answer: C) Considers the biology of the target pest

Correct answer: A – Relies solely on biological and natural control

IPM is a comprehensive approach that considers pest biology, ecology, and behavior to develop sustainable control strategies. It integrates multiple control methods (biological, cultural, chemical, mechanical) rather than relying solely on any single approach. ---

Q9: Epidemic typhus and Chagas disease can both be vectored via: A) Saliva of a vector

  1. A. Feces (frass) of a vector
  2. B. Mosquitoes
  3. C. Cockroaches
  4. D. A and B Answer: B) Feces (frass) of a vector

Correct answer: A – Feces (frass) of a vector

Both epidemic typhus (Rickettsia prowazekii via body lice) and Chagas disease (Trypanosoma cruzi via triatomine bugs) are transmitted through contaminated vector feces rubbed into bite wounds or mucous membranes, not through vector saliva. ---

Q10: Which of the following groups of Glossina species is insignificant in the transmission of Trypanosoma brucei rhodesiense? A) Palpalis group

  1. A. Morsitans group
  2. B. Fusca group
  3. C. None of the above
  4. D. All of the above Answer: A) Palpalis group

Correct answer: A – Morsitans group

The Palpalis group of tsetse flies primarily transmits T. b. gambiense (West African sleeping sickness), while the Morsitans and Fusca groups are the main vectors for T. b. rhodesiense (East African sleeping sickness). ---

Q11: Which of these habitats would be likely places for mosquito larvae to live? A) Clogged drainage ditch

  1. A. Fast flowing stream
  2. B. Lake or reservoir
  3. C. A and B
  4. D. All of the above Answer: E) All of the above

Correct answer: A – Fast flowing stream

Different mosquito species have adapted to various aquatic habitats. Culex breeds in polluted water (drainage ditches), some Anopheles species in clean flowing water, and many species utilize large water bodies like lakes and reservoirs for breeding. ---

Q12: Which of the above does NOT attract host seeking mosquitoes? A) Carbon dioxide

  1. A. Host odors
  2. B. The color white
  3. C. A and C
  4. D. All of these attract mosquitoes Answer: C) The color white

Correct answer: A – Host odors

Mosquitoes are attracted to CO₂ and host odors (lactic acid, ammonia, etc.) but are generally repelled by light colors like white. They are more attracted to dark colors (black, navy, red) which retain heat and provide visual contrast. ---

Q13: Glossina species are easily controlled by traps impregnated with which colors? A) Red and blue

  1. A. Red and white
  2. B. Blue and black
  3. C. Black and white
  4. D. Any of the above Answer: C) Blue and black

Correct answer: A – Red and white

Tsetse flies are strongly attracted to blue and black colors. This attraction is exploited in tsetse control programs using blue-black cloth traps or targets, often impregnated with insecticides for effective population control. ---

Q14: Which of the following organisms have the characteristics to be an effective mechanical vector of human disease? A) Simulium

  1. A. Culicine
  2. B. Blattella
  3. C. All of the above
  4. D. None of the above Answer: D) All of the above

Correct answer: A – Culicine

All can serve as mechanical vectors: Simulium (blackflies) can carry pathogens on mouthparts, Culicine mosquitoes can mechanically transfer pathogens between hosts, and Blattella (cockroaches) carry pathogens on their bodies and legs from contaminated areas to food/surfaces. ---

Q15: Where might you look if you suspected bedbugs have infested your house? A) Behind the headboard of the bed

  1. A. Between the mattress and the box spring
  2. B. In cavities in the bed frame
  3. C. A and B
  4. D. All of the above Answer: E) All of the above

Correct answer: A – Between the mattress and the box spring

Bedbugs hide in cracks and crevices near sleeping areas during the day. Common hiding places include behind headboards, mattress seams, box spring crevices, bed frame joints, and other furniture cracks within 8 feet of the bed. ---

Q16: Which of the following structure is part of the bacterial cell envelope? A) Peptidoglycan

  1. A. Lipopolysaccharide
  2. B. Capsule
  3. C. Gas vacuole
  4. D. Flagella Answer: A) Peptidoglycan

Correct answer: A – Lipopolysaccharide

The bacterial cell envelope consists of the cell membrane, peptidoglycan layer, and outer membrane (in gram-negatives). While LPS is part of the outer membrane and capsules surround some bacteria, peptidoglycan is the fundamental structural component of the cell wall in the envelope. ---

Q17: Microbial resistance to drugs is acquired through: A) Conjugation

  1. A. Transformation
  2. B. Transduction
  3. C. A and C
  4. D. All of the above Answer: E) All of the above

Correct answer: A – Transformation

Bacteria acquire antibiotic resistance genes through all three horizontal gene transfer mechanisms: conjugation (direct cell-to-cell transfer via pili), transformation (uptake of free DNA), and transduction (bacteriophage-mediated transfer). ---

Q18: The single most important method for classification and speciating Streptococci is: A) Agglutination using antisera against the cell wall group-specific substance

  1. A. Biochemical testing
  2. B. Capsular swelling (Quelling reaction)
  3. C. Haemolytic properties {Alpha (α), Beta (β), non haemolytic}
  4. D. None of the above Answer: A) Agglutination using antisera against the cell wall group-specific substance

Correct answer: A – Biochemical testing

The Lancefield grouping system using antisera against group-specific C carbohydrate antigens (A, B, C, etc.) is the primary method for classifying beta-hemolytic streptococci. This serological typing is more definitive than hemolysis patterns alone. ---

Q19: The specific action of haemolysin is: A) To damage white blood cells

  1. A. Cause fever
  2. B. To damage red blood cells
  3. C. Cause leukocytosis
  4. D. B and C Answer: C) To damage red blood cells

Correct answer: A – Cause fever

Hemolysins are bacterial toxins that specifically lyse red blood cells by creating pores in their membranes. This is their primary and specific action, though secondary effects may include fever due to released cellular contents. ---

Q20: Which of the following is not a symptom of septicemia? A) Fever

  1. A. Respiratory alkalosis
  2. B. Shaking chills
  3. C. High Blood Pressure
  4. D. None of the above Answer: D) High Blood Pressure

Correct answer: A – Respiratory alkalosis

Septicemia typically causes hypotension (low blood pressure) due to vasodilation and capillary leak, not hypertension. Fever, respiratory alkalosis (from hyperventilation), and shaking chills are characteristic symptoms of septicemia. ---

Q21: Certain microorganisms can never be considered to be members of the normal flora. They are always considered to be pathogens. Which of the following is true? A) Commensals

  1. A. Opportunistic pathogens
  2. B. True pathogens
  3. C. Transient pathogens
  4. D. C and D Answer: C) True pathogens

Correct answer: A – Opportunistic pathogens

True (obligate) pathogens like Mycobacterium tuberculosis, Yersinia pestis, and Plasmodium species always cause disease when they infect humans and are never part of normal flora, unlike opportunistic pathogens that can exist as commensals. ---

Q22: Which of the following conditions are associated with Streptococcus pyogenes? A) Pharyngitis

  1. A. Scarlet fever
  2. B. Rheumatic fever
  3. C. All of the above
  4. D. None of the above Answer: D) All of the above

Correct answer: A – Scarlet fever

Streptococcus pyogenes (Group A Strep) causes pharyngitis (strep throat), scarlet fever (when infected with erythrogenic toxin-producing strains), and post-infectious complications including rheumatic fever due to molecular mimicry. ---

Q23: Which of the following organisms is closely associated with dental caries? A) Streptococcus mutans

  1. A. Candida albicans
  2. B. Staphylococcus epidermidis
  3. C. Streptococcus agalactiae
  4. D. Neisseria subflava Answer: A) Streptococcus mutans

Correct answer: A – Candida albicans

Streptococcus mutans is the primary etiologic agent of dental caries. It adheres strongly to tooth surfaces, produces acids from dietary sugars that demineralize tooth enamel, and forms biofilms (dental plaque). ---

Q24: The microbial factor responsible for cholera diarrhea is a toxin that: A) Blocks EF-2

  1. A. Cleaves AMP
  2. B. Cleaves SNARE
  3. C. Yields increase intracellular levels of cAMP
  4. D. Block EF-1 dependent binding of amino-acyl-tRNA to ribosomes Answer: D) Yields increase intracellular levels of cAMP

Correct answer: A – Cleaves AMP

Cholera toxin ADP-ribosylates the Gs protein, permanently activating adenylyl cyclase, leading to massive cAMP accumulation in intestinal epithelial cells. This causes massive secretion of chloride, sodium, and water into the intestinal lumen. ---

Q25: A 20-year old university student complains of dysuria, frequency and urgency on urination for 24 hours. She has become sexually active. Urinalysis shows many polymorphonuclear cells, the most likely organism responsible for the signs and symptoms is: A) Staphylococcus aureus

  1. A. Streptococcus agalactiae
  2. B. Lactobacillus species
  3. C. Gardnerella vaginalis
  4. D. Escherichia coli Answer: E) Escherichia coli

Correct answer: A – Streptococcus agalactiae

E. coli causes 80-90% of uncomplicated urinary tract infections in young, sexually active women. The classic presentation includes dysuria, frequency, urgency, and pyuria (PMNs in urine). Sexual activity increases risk by introducing bacteria into the urinary tract. ---

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