Medical Bacteriology and Entomology Exam 2018/2019 – 32 MCQs | Kenya MBChB

32 Year 2: Microbiology exam questions on Medical Bacteriology and Entomology Exam 2018/2019 for medical students. Includes MCQs, answers, explanations and writ

This MCQ set contains 32 questions on Medical Bacteriology and Entomology Exam 2018/2019 in the Year 2: Microbiology unit. Each question includes the correct answer and a detailed explanation for active recall and exam preparation.

Q1: Question 1 An outbreak of sepsis caused by Staphylococcus aureus has occurred in the newborn nursery. What is the most likely source of the organism? A) Nose

  1. A. Nose
  2. B. Colon
  3. C. Hand
  4. D. Throat
  5. E. Nose

Correct answer: A – Nose

S. aureus is commonly carried asymptomatically in the anterior nares (nose) of 20-40% of healthy individuals. Healthcare workers' nasal carriage is often the source of nosocomial outbreaks in nurseries.

Q2: Question 2 Each of the following agents is a recognized cause of diarrhea except: A) Clostridium perfringens

  1. A. Clostridium perfringens
  2. B. Vibrio cholerae
  3. C. Enterococcus faecalis
  4. D. Escherichia coli
  5. E. Enterococcus faecalis

Correct answer: C – Enterococcus faecalis

Enterococcus faecalis is normal gut flora and typically doesn't cause diarrhea. The others are established diarrheal pathogens: C. perfringens (food poisoning), V. cholerae (cholera), and E. coli (various diarrheal syndromes).

Q3: Question 3 Bacterial identification by serological tests is based on specific antigens. Which component is least likely to contain useful antigens? A) Capsule

  1. A. Capsule
  2. B. Cell wall
  3. C. Flagella
  4. D. Ribosome
  5. E. Ribosome

Correct answer: D – Ribosome

Ribosomes are internal cellular structures not exposed on the bacterial surface, making them poor targets for serological identification. Capsule, cell wall, and flagella are surface-exposed and highly antigenic.

Q4: Question 4 Which Pasteurella species has been associated with female genital tract and newborn infections? A) Pasteurella multocida

  1. A. Pasteurella multocida
  2. B. Pasteurella pneumotropica
  3. C. Pasteurella ureae
  4. D. Pasteurella bettyae
  5. E. Pasteurella bettyae

Correct answer: D – Pasteurella bettyae

P. bettyae is associated with human genital tract infections and can cause neonatal infections. P. multocida typically causes wound infections after animal bites.

Q5: Question 5 Each statement about streptococci classification is correct except: A) Pneumococci are alpha-hemolytic and can be serotyped based on polysaccharide capsule

  1. A. Pneumococci are alpha-hemolytic and can be serotyped based on polysaccharide capsule
  2. B. Enterococci are group D streptococci and grow in 6.5% NaCl
  3. C. Viridans streptococci are identified by Lancefield grouping based on C carbohydrate
  4. D. Pneumococci and viridans streptococci can be differentiated by bile solubility and optochin susceptibility
  5. E. Viridans streptococci are identified by Lancefield grouping based on C carbohydrate

Correct answer: C – Viridans streptococci are identified by Lancefield grouping based on C carbohydrate

Viridans streptococci typically lack the C carbohydrate antigen and are not classified by Lancefield grouping. They are identified by biochemical tests and alpha-hemolysis pattern.

Q6: Staphylococcal scalded skin syndrome is caused by exotoxin produced by: A) Streptococcus pyogenes

  1. A. Streptococcus pyogenes
  2. B. Pseudomonas aeruginosa
  3. C. Staphylococcus aureus
  4. D. Propionibacterium acnes
  5. E. Demodex folliculorum

Correct answer: C – Staphylococcus aureus

Staphylococcal scalded skin syndrome is caused by exfoliative toxins (exfoliatins A and B) produced by certain strains of S. aureus . These toxins cause separation of the epidermis.

Q7: Question 7 A pregnant woman with previous syphilis treatment shows: RPR non-reactive, TP-PA reactive. Which statement is most correct? A) The baby is at risk for congenital syphilis

  1. A. The baby is at risk for congenital syphilis
  2. B. The mother needs lumbar puncture and CSF VDRL for neurosyphilis
  3. C. The mother's previous treatment for syphilis was effective
  4. D. The mother needs immediate re-treatment
  5. E. The mother's previous treatment for syphilis was effective

Correct answer: C – The mother's previous treatment for syphilis was effective

Non-reactive RPR with reactive treponemal test indicates past treated syphilis. The treponemal test remains positive for life, while non-treponemal tests become negative after successful treatment.

Q8: Question 8 Which bacteria has the lowest 50% infective dose (ID50)? A) Campylobacter jejuni

  1. A. Campylobacter jejuni
  2. B. Salmonella typhi
  3. C. Shigella sonnei
  4. D. Vibrio cholerae
  5. E. Shigella sonnei

Correct answer: C – Shigella sonnei

Shigella species have extremely low infectious doses (10-100 organisms), making them highly contagious. Salmonella and V. cholerae require much higher doses (10⁴-10⁶ organisms).

Q9: Which disease is best diagnosed by serologic means? A) Pulmonary tuberculosis

  1. A. Pulmonary tuberculosis
  2. B. Gonorrhea
  3. C. Actinomycosis
  4. D. Typhoid fever
  5. E. Typhoid fever

Correct answer: D – Typhoid fever

Typhoid fever is often diagnosed serologically using the Widal test (though blood culture is gold standard). The others are better diagnosed by direct methods: TB (sputum AFB), gonorrhea (culture/PCR), actinomycosis (direct examination).

Q10: Question 10 A woman has non-bloody diarrhea for 14 hours. Which organism is least likely to cause this? A) Streptococcus pyogenes

  1. A. Streptococcus pyogenes
  2. B. Clostridium difficile
  3. C. Shigella dysenteriae
  4. D. Salmonella enteritidis
  5. E. Streptococcus pyogenes

Correct answer: A – Streptococcus pyogenes

S. pyogenes causes pharyngitis, cellulitis, and invasive infections but not gastroenteritis. The others are established causes of diarrhea.

Q11: A woman develops gonococcal PID. What is the most common sequela? A) Cancer of the cervix

  1. A. Cancer of the cervix
  2. B. Urethral stricture
  3. C. Uterine fibroid tumors
  4. D. Infertility
  5. E. Vaginal-rectal fistula

Correct answer: D – Infertility

Gonococcal PID commonly causes fallopian tube scarring and adhesions, leading to infertility and increased risk of ectopic pregnancy.

Q12: Mycobacterial survival after macrophage ingestion is attributed to: A) Inhibition of complement activation

  1. A. Inhibition of complement activation
  2. B. Poor immunogenicity of cell wall glycolipids
  3. C. Inhibition of phagosome formation and endosomal acidification
  4. D. Resistance to oxygen radicals in phagolysosome
  5. E. Rapid escape from endosome to cytoplasm

Correct answer: C – Inhibition of phagosome formation and endosomal acidification

Mycobacteria prevent phagosome-lysosome fusion and inhibit acidification of the phagosome, allowing survival within macrophages.

Q13: The molecular basis for cholera toxin's effect on duodenal cells is: A) Inactivation of Gi protein

  1. A. Inactivation of Gi protein
  2. B. Increased generation of cyclic AMP
  3. C. Activation of adenylyl cyclase
  4. D. Increased activity of potassium pumps
  5. E. Ribosylation of GTP-binding protein

Correct answer: E – Ribosylation of GTP-binding protein

Cholera toxin ADP-ribosylates the Gs protein, preventing GTPase activity and leading to continuous adenylyl cyclase activation and cAMP production.

Q14: Bacterial capsules function as virulence factors by interfering with: A) Antibiotic penetration

  1. A. Antibiotic penetration
  2. B. Antibody binding
  3. C. B lymphocyte activation
  4. D. Interferon-γ release
  5. E. Phagocytosis

Correct answer: E – Phagocytosis

Bacterial capsules are antiphagocytic, making it difficult for neutrophils and macrophages to engulf and destroy encapsulated bacteria.

Q15: Question 15 Which is NOT a major cause of acute bacterial meningitis? A) Streptococcus pneumoniae

  1. A. Streptococcus pneumoniae
  2. B. Neisseria meningitidis
  3. C. Streptococcus pyogenes
  4. D. Haemophilus influenzae
  5. E. Streptococcus pyogenes

Correct answer: C – Streptococcus pyogenes

S. pyogenes rarely causes meningitis. The classic triad of bacterial meningitis pathogens includes S. pneumoniae , N. meningitidis , and H. influenzae .

Q16: A woman with UTI has gram-negative, lactose-fermenting, indole-positive bacilli. The organism's effectiveness in causing UTI is associated with: A) Exotoxins

  1. A. Exotoxins
  2. B. K antigens
  3. C. P fimbriae
  4. D. Plasmids
  5. E. Metabolic properties

Correct answer: C – P fimbriae

This describes E. coli . P fimbriae allow adherence to uroepithelial cells with P blood group antigens, facilitating ascending UTI and pyelonephritis.

Q17: Question 17 The coagulase test differentiates: A) S. epidermidis from N. meningitidis

  1. A. S. epidermidis from N. meningitidis
  2. B. S. aureus from S. epidermidis
  3. C. S. pyogenes from S. aureus
  4. D. S. pyogenes from E. faecalis
  5. E. S. aureus from S. epidermidis

Correct answer: B – S. aureus from S. epidermidis

The coagulase test distinguishes coagulase-positive S. aureus from coagulase-negative staphylococci like S. epidermidis .

Q18: Snails are both first and second intermediate hosts of: A) Echinostoma ilocanum

  1. A. Echinostoma ilocanum
  2. B. Fasciola hepatica
  3. C. Fasciolopsis buski
  4. D. Hymenolepis nana
  5. E. Paragonimus westermanii

Correct answer: A – Echinostoma ilocanum

E. ilocanum uses the same snail species as both first and second intermediate hosts, unlike other flukes that use different intermediate hosts.

Q19: How can millipedes cause medical problems? A) Stinging

  1. A. Stinging
  2. B. Spraying defensive secretions
  3. C. Transmitting viruses
  4. D. Laying eggs under skin
  5. E. None of the above

Correct answer: B – Spraying defensive secretions

Millipedes secrete defensive chemicals (hydrogen cyanide, quinones, phenols) that can cause skin burns, eye irritation, and respiratory problems.

Q20: Holometabolous insects have: A) 2 life stages

  1. A. 2 life stages
  2. B. 3 life stages
  3. C. 4 life stages
  4. D. 1 life stage
  5. E. None of above

Correct answer: C – 4 life stages

Holometabolous insects undergo complete metamorphosis with four stages: egg → larva → pupa → adult. Examples include flies, beetles, and butterflies.

Q21: Rift Valley fever is mainly transmitted by: A) Culex species

  1. A. Culex species
  2. B. Aedes species
  3. C. Anopheles species
  4. D. Toxorhynchites species
  5. E. All of the above

Correct answer: B – Aedes species

Rift Valley fever is primarily transmitted by Aedes mosquitoes, especially flood-water Aedes species in endemic areas of Africa.

Q22: Autogenous insects: A) Lay eggs without mating

  1. A. Lay eggs without mating
  2. B. Mate but do not lay eggs
  3. C. Are blood seekers
  4. D. Are sugar feeders
  5. E. None of the above

Correct answer: A – Lay eggs without mating

Autogenous insects can produce their first batch of eggs without taking a blood meal, using stored nutrients from their larval development.

Q23: Parthenogenesis is a type of: A) Asexual reproduction with offspring from unfertilized eggs

  1. A. Asexual reproduction with offspring from unfertilized eggs
  2. B. Asexual reproduction with offspring from fertilized eggs
  3. C. Sexual reproduction with offspring from fertilized eggs
  4. D. Sexual reproduction with offspring from unfertilized eggs
  5. E. None of the above

Correct answer: A – Asexual reproduction with offspring from unfertilized eggs

Parthenogenesis is asexual reproduction where embryos develop from unfertilized eggs, producing genetic clones of the parent.

Q24: The best mode of malaria control is: A) Elimination of insect eggs

  1. A. Elimination of insect eggs
  2. B. Bed net use
  3. C. Prompt treatment
  4. D. Integrated vector management
  5. E. All of the above

Correct answer: D – Integrated vector management

IVM combines multiple approaches (bed nets, treatment, environmental management, surveillance) for sustainable malaria control, more effective than single interventions.

Q25: Which insects are included in order Blattaria? A) Cockroaches

  1. A. Cockroaches
  2. B. Lice
  3. C. True flies
  4. D. Beetles
  5. E. All of the above

Correct answer: A – Cockroaches

Order Blattaria (now Blattodea) includes cockroaches and termites. Lice belong to Phthiraptera, flies to Diptera, and beetles to Coleoptera.

View on OmpathStudy