Medical Bacteriology and Parasitology Exam 2024/2025 MCQs

34 clinical MCQs in Microbiology. Fish are second intermediate hosts of?. Kenya, Africa and global revision.

Questions, Answers & Explanations

1. Q1. Fish are second intermediate hosts of?

   • Echinostoma ilocaanum
   • Hepatic fascia
   • Fasciolopsis buski
   • Hymenolepis nana
   • Clonorchis sinensis

   Answer: Clonorchis sinensis

   Explanation: Fish serve as the second intermediate host for Clonorchis sinensis (Chinese liver fluke). Humans get infected by eating raw or undercooked fish containing the parasite's metacercariae. ---

2. Q2. Which of the following secretes defensive secretions to cause irritation on human skin?

   • Millipedes
   • Centipedes
   • American killer
   • Enterobius vermicularis
   • All of the above

   Answer: Millipedes

   Explanation: Millipedes have defensive glands that secrete irritating chemicals (benzoquinones, hydrogen cyanide) causing skin burns and discoloration. ---

3. Q3. Holometabolous insects have?

   • 2 life stages
   • 3 life stages
   • 4 life stages
   • 5 life stages
   • 1 life stage

   Answer: 2 life stages

   Explanation: Holometabolous insects undergo complete metamorphosis with four stages: egg → larva → pupa → adult. ---

4. Q4. Which of the following transmits parasites for river blindness?

   • Culex species
   • Chrysops species
   • Simulium species
   • Toxorhynchitinae species
   • All of the above

   Answer: Simulium species

   Explanation: Simulium species (blackflies) are the vectors of Onchocerca volvulus, causing river blindness (onchocerciasis). ---

5. Q5. Which insecticide targets GABA in its action?

   • DDT
   • DEET
   • Permethrin
   • Bendiocarb
   • Malathion

   Answer: Bendiocarb

   Explanation: Bendiocarb is a carbamate insecticide that inhibits acetylcholinesterase, affecting GABA neurotransmission. ---

6. Q6. Presence of triatomine bugs could predispose the population to?

   • Sleeping sickness
   • Leishmaniasis
   • Malaria
   • Chagas disease
   • River blindness

   Answer: Chagas disease

   Explanation: Triatomine bugs (kissing bugs) transmit Trypanosoma cruzi, which causes Chagas disease. ---

7. Q7. People living in forested areas are at a risk of?

   • Sleeping sickness
   • Leishmaniasis
   • Malaria
   • Encephalitis
   • River blindness

   Answer: Sleeping sickness

   Explanation: Forested areas harbor sandflies (Phlebotomus/Lutzomyia species) that transmit Leishmania parasites. ---

8. Q8. Which of the following insects are commonly found in Latin America?

   • Glossina species
   • Triatomine bugs
   • Cimex species
   • Chrysops species
   • Steam bugs

   Answer: Glossina species

   Explanation: Triatomine bugs are endemic to Latin America where they transmit Chagas disease. Glossina species (tsetse flies) are found in sub-Saharan Africa. ---

9. Q9. Pruritus can be best diagnosed for?

   • Sarcoptes scabiei
   • Leptothrombidium species
   • Blattella species
   • Pediculus species
   • Pthirus species

   Answer: Sarcoptes scabiei

   Explanation: Sarcoptes scabiei (scabies mite) burrows into skin causing intense pruritus (itching), especially at night. ---

10. Q10. If you found lice eggs (nits) in someone's clothing, what species would they most likely be from?

    • Crab lice
    • Pediculus humanus
    • Pediculus capitis
    • Pthirus species
    • All of the above

    Answer: Pediculus humanus

    Explanation: Pediculus humanus (body lice) live and lay eggs in clothing seams, unlike head lice which attach to hair. ---

11. Q11. Which of the following is odd one out in terms of transmission?

    • Vibrio cholerae
    • Entamoeba histolytica
    • Rotavirus
    • Thelazia species
    • None of the above

    Answer: Thelazia species

    Explanation: Thelazia species (eye worm) is transmitted by flies (mechanical vectors), while the others are fecal-oral. ---

12. Q12. Which one of the following is larviparous?

    • Phlebotomus species
    • Lutzomyia species
    • Triatomine bugs
    • Glossina gambiense
    • Dermacentor species

    Answer: Phlebotomus species

    Explanation: Glossina species (tsetse flies) are larviparous—they give birth to live larvae rather than laying eggs. ---

13. Q13. Argasid ticks have?

    • One host
    • Two hosts
    • Three hosts
    • Multiple hosts
    • Four hosts

    Answer: One host

    Explanation: Argasid (soft) ticks are multi-host ticks that feed quickly on different hosts throughout their life stages. ---

14. Q14. Ixodid ticks have nymphal stages.

    • One
    • Two
    • Three
    • Four
    • Multiple

    Answer: One

    Explanation: Ixodid (hard) ticks have a single nymphal stage: egg → larva → nymph → adult. ---

15. Q15. Traps for Aedes mosquitoes are composed of?

    • Aedes mosquitoes
    • Black and blue colors
    • White and blue colors
    • White only
    • Black only

    Answer: Aedes mosquitoes

    Explanation: Aedes mosquitoes are attracted to contrasting black and white patterns. ---

16. Q16. Traps for Glossina species are composed of?

    • Black and white colors
    • Black and blue colors
    • White and blue colors
    • White only
    • Black only

    Answer: Black and blue colors

    Explanation: Tsetse flies (Glossina species) are attracted to black and blue colors. ---

17. Q17. Black water disease is due to presence of in the environment.

    • Blackwater fever
    • Anopheles species
    • Culicoides species
    • Lutzomyia species
    • Musca species

    Answer: Blackwater fever

    Explanation: Blackwater fever is a complication of falciparum malaria, transmitted by Anopheles mosquitoes. ---

18. Q18. Hepatitis B virus has been associated with?

    • Cimex species
    • Xenopsylla species
    • Pthirus species
    • Tabanids species
    • Steam bugs

    Answer: Cimex species

    Explanation: Cimex species (bed bugs) have been studied for potential mechanical transmission of Hepatitis B. ---

19. Q19. Which of the following statements regarding vaccination for Bacillus anthracis is correct? ---

    • It is routinely available for all citizens
    • Recombinant vaccine trials have shown good safety and efficacy
    • The current vaccine is well tolerated
    • A single dose is adequate after exposure to spores
    • Vaccination of animals is not useful

    Answer: It is routinely available for all citizens

20. Q20. Lowenstein Jensen media is used to isolate?

    • LJ medium
    • Proteus species
    • coli
    • Mycobacterium tuberculosis
    • None of the above

    Answer: LJ medium

    Explanation: LJ medium is an egg-based selective medium for culturing mycobacteria. ---

21. Q21. All of the following statements regarding Clostridium perfringens are correct EXCEPT

    • Clostridioides difficile
    • It produces a double zone of β-hemolysis when grown on blood agar
    • Some strains are aerotolerant
    • It is the most common cause of antibiotic-associated diarrhea
    • It can cause intravascular hemolysis

    Answer: Clostridioides difficile

    Explanation: Clostridioides difficile is the primary cause of antibiotic-associated diarrhea. ---

22. Q22. Motility of the bacteria can be observed by ---

    • Hanging drop method
    • Soft agar method
    • Both "A" and "B"
    • Pour plate method
    • All the above

    Answer: Hanging drop method

23. Q23. A 53-year-old woman with breast cancer develops a cough and progressive weakness. Gram stain of sputum shows branching gram-positive rods that were partially acid fast. Which organism is the cause?

    • Actinomyces israelii
    • Corynebacterium pseudodiphtheriticum
    • Aspergillus fumigatus
    • Nocardia farcinica
    • Erysipelothrix rhusiopathiae

    Answer: Actinomyces israelii

    Explanation: Branching gram-positive, partially acid-fast rods in an immunocompromised patient with pulmonary and CNS symptoms are characteristic of Nocardia. ---

24. Q24. The drug of choice to treat Nocardia infection is ---

    • Penicillin G
    • Trimethoprim-sulfamethoxazole
    • Gentamicin
    • Amphotericin B
    • A third-generation cephalosporin

    Answer: Penicillin G

25. Q25. Which can cause food INTOXICATION?

    • S. aureus
    • Streptococcus pyogenes
    • coli
    • Salmonella
    • None above

    Answer: S. aureus

    Explanation: S. aureus produces preformed enterotoxins in food. ---

26. Q26. Helicobacter pylori possesses that helps to neutralize stomach acid (HCl). ---

    • Coagulase
    • Urease
    • Hyaluronidase
    • Catalase
    • Lipase

    Answer: Coagulase

27. Q27. An 8-year-old boy with a grayish pseudomembrane over the tonsils. The cause is most likely

    • A gram-negative bacillus
    • A single-stranded positive-sense RNA virus
    • A catalase-positive gram-positive coccus
    • A club-shaped gram-positive bacillus
    • A double stranded RNA virus

    Answer: A gram-negative bacillus

    Explanation: This describes Corynebacterium diphtheriae. ---

28. Q28. The primary mechanism in the pathogenesis of diphtheria is ---

    • Increase in cAMP
    • Action of superantigen
    • Inactivation of acetylcholine esterase
    • Action of enterotoxin A
    • Inactivation of elongation factor 2

    Answer: Increase in cAMP

29. Q29. Which of the following aerobic gram-positive bacilli is modified acid-fast positive? ---

    • Nocardia brasiliensis
    • Lactobacillus acidophilus
    • Erysipelothrix rhusiopathiae
    • Listeria monocytogenes
    • Occurs only after chronic exposure

    Answer: Nocardia brasiliensis

30. Q30. A fisherman with a violaceous nodule on his finger. Culture shows gram-positive bacilli causing greenish discoloration and long filaments in broth. The cause is ---

    • Lactobacillus acidophilus
    • Erysipelothrix rhusiopathiae
    • Listeria monocytogenes
    • Rhodococcus equi
    • Nocardia brasiliensis

    Answer: Lactobacillus acidophilus

31. Q31. A biochemical reaction useful in the identification of Erysipelothrix rhusiopathiae is ---

    • Catalase positivity
    • Acid fastness
    • Esculin hydrolysis
    • Tumbling motility
    • Production of H2S

    Answer: Catalase positivity

32. Q32. A catheterized patient develops bladder stones. Urine culture grows a short, irregular gram-positive rod. The organism is ---

    • Corynebacterium urealyticum
    • Nocardia brasiliensis
    • Actinomadura
    • Erysipelothrix
    • Usually mediated by non-specific mechanisms

    Answer: Corynebacterium urealyticum

33. Q33. Drug of choice for treatment of mycoplasma infection are ---

    • Tetracycline
    • Erythromycin
    • A and B
    • Penicillin
    • Mostly unchanged in early disease

    Answer: Tetracycline

34. Q34. The mode of spread of tetanus neurotoxin from blood to brain is via

    • Lymphatics
    • Arterial blood
    • Cranial nerve
    • None of the above
    • Reduced by routine feedback control

    Answer: Lymphatics

    Explanation: Tetanus toxin spreads via retrograde axonal transport.