🧪 Questions 1–10: General D.

Catalase test
✅ Answer: B
Principles 7. Which Gram-negative bacterium is
associated with hospital-acquired
1. Which of the following is a common pneumonia?
feature of Gram-negative bacteria? A. Legionella pneumophila
A. Thick peptidoglycan layer B. Haemophilus influenzae
B. Presence of teichoic acid C. Klebsiella pneumoniae
C. Outer membrane with D. Bordetella pertussis
lipopolysaccharide (LPS) ✅ Answer: C
D. No periplasmic space 8. First-line treatment for severe
✅ Answer: C Salmonella typhi infection?
2. Lipid A component of LPS is A. Amoxicillin
responsible for which clinical effect? B. Ciprofloxacin
A. Immune evasion C. Metronidazole
B. Endotoxic shock D. Penicillin G
C. Bacterial motility ✅ Answer: B
D. Antigenic variation 9. Whooping cough is caused by:
✅ Answer: B A. Bordetella bronchiseptica
3. A 23-year-old male presents with B. Bordetella pertussis
dysuria and purulent urethral C. Haemophilus influenzae
discharge. Likely cause? D. Moraxella catarrhalis
A. Neisseria gonorrhoeae ✅ Answer: B
B. Escherichia coli 10. A lactose-negative, hydrogen
C. Klebsiella pneumoniae sulfide-producing, motile GNR is
D. Treponema pallidum likely:
✅ Answer: A A. Shigella flexneri
4. Which bacteria shows swarming B. Salmonella typhimurium
motility on agar? C. Escherichia coli
A. Salmonella enterica D. Klebsiella pneumoniae
B. Proteus mirabilis ✅ Answer: B
C. Shigella dysenteriae
D. Neisseria meningitidis
✅ Answer: B
5. A major virulence factor of
Klebsiella pneumoniae is:
🧪 Questions 11–20:
A. Endotoxin Enterobacteriaceae
B. Capsule
C. Flagella 11. What selective medium is used to
D. Pili isolate Salmonella and Shigella?
✅ Answer: B A. Chocolate agar
6. Test that differentiates Neisseria B. MacConkey agar
gonorrhoeae from N. meningitidis? C. Hektoen enteric agar
A. Oxidase test D. Blood agar
B. Glucose fermentation test ✅ Answer: C
C. Gram stain
12. Enzyme produced by Proteus species D. Pseudomonas aeruginosa
that contributes to stone formation? ✅ Answer: B
A. Catalase 19. Notable feature of Klebsiella
B. Oxidase pneumoniae?
C. Urease A. Swarming motility
D. β-lactamase B. Green pigment
✅ Answer: C C. Prominent capsule
13. E. coli O157:H7 is associated with: D. Shiga toxin
A. Typhoid fever ✅ Answer: C
B. Traveler’s diarrhea 20. Test used to differentiate lactose
C. Hemolytic uremic syndrome fermenters?
D. Cholera-like diarrhea A. Catalase
✅ Answer: C B. TSI agar
14. Which Enterobacteriaceae member C. Coagulase
is H₂S-positive and motile? D. Blood agar hemolysis
A. Shigella dysenteriae ✅ Answer: B
B. Salmonella typhi
C. Klebsiella pneumoniae
D. Escherichia coli
✅ Answer: B
15. What distinguishes Shigella from
🧫 Questions 21–30:
Salmonella? Neisseria & Haemophilus
A. H₂S production
B. Motility 21. Sugar fermented by Neisseria
C. Capsule meningitidis but not N.
D. Gram stain appearance gonorrhoeae?
✅ Answer: A A. Glucose
16. Toxin that mediates watery diarrhea B. Maltose
in ETEC? C. Sucrose
A. Shiga toxin D. Fructose
B. Cholera toxin ✅ Answer: B
C. Heat-labile toxin 22. Primary virulence factor of N.
D. Lipid A meningitidis?
✅ Answer: C A. Pili
17. E. coli strain causing infantile B. Capsule
diarrhea? C. Endotoxin
A. EIEC D. IgA protease
B. EHEC ✅ Answer: B
C. ETEC 23. N. gonorrhoeae is cultured on:
D. EPEC A. Blood agar
✅ Answer: D B. Thayer-Martin agar
18. Lactose fermenter on MacConkey C. Chocolate agar
agar? D. EMB agar
A. Proteus mirabilis ✅ Answer: B
B. Escherichia coli 24. Which condition is N. meningitidis
C. Salmonella typhi associated with?
 A. PID
B. Meningitis
🧼 Questions 31–40:
C. Urethritis Bordetella & Pseudomonas
D. Ophthalmia neonatorum
✅ Answer: B 31. Main virulence factor causing cough
25. Moraxella catarrhalis often causes: in pertussis?
A. Typhoid fever A. Capsule
B. Otitis media B. Pertussis toxin
C. UTI C. Tracheal cytotoxin
D. Whooping cough D. Lipooligosaccharide
✅ Answer: B ✅ Answer: C
26. Growth of H. influenzae requires: 32. Best medium for Bordetella
A. A and B factors pertussis?
B. X and V factors A. TCBS
C. C and D B. Thayer-Martin
D. P and Q C. Bordet-Gengou
✅ Answer: B D. EMB
27. The HiB vaccine protects against: ✅ Answer: C
A. Pili 33. Bordetella pertussis causes:
B. Outer membrane protein A. Scarlet fever
C. Type B capsule (PRP) B. Whooping cough
D. Endotoxin C. Tetanus
✅ Answer: C D. Diphtheria
28. Which illness is NOT caused by H. ✅ Answer: B
influenzae? 34. Stage with paroxysmal cough in
A. Epiglottitis pertussis?
B. Meningitis A. Incubation
C. Otitis media B. Catarrhal
D. Cholera C. Paroxysmal
✅ Answer: D D. Convalescent
29. A child with stridor and "thumb ✅ Answer: C
sign" likely has: 35. DTaP vaccine protects against:
A. Bronchiolitis A. Diphtheria, Tetanus, Pertussis
B. Croup B. Diarrhea, Typhoid, Anthrax
C. Epiglottitis C. Dengue, Typhus, Parainfluenza
D. Asthma D. Diphyllobothrium, Tetanus,
✅ Answer: C Pseudomonas
30. Standard treatment for H. influenzae? ✅ Answer: A
A. Penicillin 36. Pigment produced by Pseudomonas
B. Ceftriaxone aeruginosa?
C. Vancomycin A. Pyocyanin
D. Tetracycline B. Biliverdin
✅ Answer: B C. Hemocyanin
D. Flavoprotein
✅ Answer: A
 37. Pseudomonas is most associated 43. Curved, oxidase-positive Gram-
with: negative rod?
A. Cystic fibrosis pneumonia A. E. coli
B. Scarlet fever B. Shigella
C. Tuberculosis C. Vibrio cholerae
D. Pharyngitis D. Klebsiella
✅ Answer: A ✅ Answer: C
38. Resistance of Pseudomonas is due 44. Optimal growth temp for
to: Campylobacter jejuni?
A. Capsule A. 25°C
B. Spore formation B. 37°C
C. Efflux pumps/porin changes C. 42°C
D. Beta-lactamase only D. 55°C
✅ Answer: C ✅ Answer: C
39. Acinetobacter baumannii is linked 45. Bacteria associated with Guillain-
to: Barré syndrome?
A. Otitis externa A. H. pylori
B. CAP B. Shigella
C. MDR hospital infections C. Campylobacter jejuni
D. Diarrhea D. Vibrio vulnificus
✅ Answer: C ✅ Answer: C
40. Fruity odor in wound culture 46. Common diagnostic test for H.
suggests: pylori?
A. E. coli A. Urine culture
B. Pseudomonas aeruginosa B. Urea breath test
C. Proteus mirabilis C. Blood smear
D. Klebsiella pneumoniae D. CSF analysis
✅ Answer: B ✅ Answer: B
47. Enzyme allowing H. pylori to
survive acidity?
A. Catalase
Questions 41–50: Vibrio, Campylobacter, B. Urease
Helicobacter, and Miscellaneous C. Protease
D. Oxidase
41. Hallmark symptom of cholera? ✅ Answer: B
A. Bloody diarrhea 48. H. pylori is linked to all EXCEPT:
B. Rice-water stools A. Gastric ulcers
C. Constipation B. Duodenal ulcers
D. Dysentery C. MALT lymphoma
✅ Answer: B D. Rheumatic fever
42. Best medium for Vibrio cholerae? ✅ Answer: D
A. MacConkey 49. Legionella pneumophila is best
B. Chocolate detected by:
C. TCBS A. Gram stain
D. Blood agar B. Silver stain or urine antigen test
✅ Answer: C C. Blood culture
 D. Rapid strep test 56. 60-year-old smoker with green
✅ Answer: B sputum pneumonia:
50. Legionella thrives in: A. Strep pneumo
A. Soil B. Pseudomonas
B. Contaminated water systems C. Mycoplasma
C. Human GI tract D. Klebsiella
D. Domestic pets ✅ Answer: B
✅ Answer: B 57. 6-month-old with paroxysmal cough
and vomiting:
A. Strep pyogenes
B. H. influenzae
🧬 Questions 51–60: Zoonoses & Clinical C. B. pertussis
Scenarios D. Staph aureus
✅ Answer: C
51. Francisella tularensis is transmitted 58. Patient with PUD and positive urease
by: test:
A. Droplets A. E. coli
B. Tick or deer fly bite B. Campylobacter
C. Contaminated food C. H. pylori
D. Water D. Shigella
✅ Answer: B ✅ Answer: C
52. Yersinia enterocolitica mimics: 59. Healthcare worker with red, swollen
A. Meningitis puncture wound:
B. Appendicitis A. E. coli
C. Hepatitis B. Klebsiella
D. Otitis media C. Pseudomonas
✅ Answer: B D. H. influenzae
53. Bubonic plague is caused by: ✅ Answer: C
A. Brucella abortus 60. Oyster consumption followed by
B. Yersinia pestis sepsis suggests:
C. Francisella tularensis A. Salmonella
D. Pasteurella multocida B. Vibrio vulnificus
✅ Answer: B C. E. coli
54. Brucella infection is linked to: D. Campylobacter
A. Undercooked fish ✅ Answer: B
B. Raw dairy
C. Poultry
D. Mosquito bites
🧫 Questions 61–70: Clinical
✅ Answer: B Cases & Zoonotic
55. Pasteurella multocida is acquired
through:
Infections
A. Rodents
61. A 35-year-old with ulceroglandular
B. Soil
lymphadenopathy after rabbit skinning
C. Cat or dog bites
likely has:
D. Human contact
A. Brucella abortus
✅ Answer: C
B. Francisella tularensis
C. Pasteurella multocida D. Shigella sonnei
D. Yersinia pestis ✅ Answer: B
✅ Answer: B
67. A 4-year-old child presents with
62. A Gram-negative rod with bipolar abdominal pain, fever, and
staining and flea-borne transmission most pseudoappendicitis. What is the likely
likely indicates: causative agent?
A. Yersinia pestis A. E. coli O157:H7
B. Yersinia enterocolitica B. Yersinia enterocolitica
C. Brucella melitensis C. Salmonella typhi
D. Francisella tularensis D. Campylobacter jejuni
✅ Answer: A ✅ Answer: B

63. An outbreak of gastroenteritis traced to 68. A patient’s stool culture grows curved
unpasteurized milk in a daycare is most Gram-negative rods that grow at 42°C.
likely caused by: Likely pathogen?
A. Shigella flexneri A. Salmonella
B. Yersinia enterocolitica B. Vibrio cholerae
C. Campylobacter jejuni C. Campylobacter jejuni
D. E. coli D. Escherichia coli
✅ Answer: C ✅ Answer: C

64. Which zoonotic Gram-negative 69. Which Gram-negative pathogen causes

bacterium causes undulating fever and is typhoid fever and can be diagnosed with the
transmitted via unpasteurized dairy? Widal test?
A. Brucella melitensis A. Shigella flexneri
B. Pasteurella multocida B. E. coli
C. Yersinia enterocolitica C. Salmonella typhi
D. Salmonella enterica D. Yersinia pestis
✅ Answer: A ✅ Answer: C

65. A man bitten by a dog presents with 70. After returning from a cruise, multiple
cellulitis. Which organism is most likely passengers develop profuse, painless watery
responsible? diarrhea. The likely pathogen is:
A. Francisella tularensis A. Norovirus
B. Pasteurella multocida B. Vibrio cholerae
C. Brucella abortus C. Salmonella enterica
D. Staphylococcus aureus D. E. coli O157:H7
✅ Answer: B ✅ Answer: B

66. A diabetic patient with a necrotic wound ⚠️Questions 71–80: Pathogenesis and
and grape-like odor is most likely infected Diagnostics
with:
A. E. coli 71. What part of Gram-negative bacteria
B. Pseudomonas aeruginosa causes sepsis?
C. Klebsiella pneumoniae A. Peptidoglycan
 B. Lipopolysaccharide (LPS) B. Inhibits RNA polymerase
C. Pili C. Inhibits DNA replication
D. Teichoic acid D. Blocks cell membrane
✅ Answer: B ✅ Answer: A
72. The Widal test detects antibodies 79. Bite wound with Gram-negative
against: rods:
A. E. coli A. Haemophilus influenzae
B. Salmonella typhi B. Yersinia enterocolitica
C. H. pylori C. Pasteurella multocida
D. Klebsiella D. B. pertussis
✅ Answer: B ✅ Answer: C
73. Which organism does NOT ferment 80. Green pigment, lactose-negative,
glucose? oxidase-positive bacilli?
A. E. coli A. E. coli
B. Shigella B. Klebsiella
C. Pseudomonas aeruginosa C. Pseudomonas aeruginosa
D. Salmonella D. Proteus
✅ Answer: C ✅ Answer: C
74. Shigella invades which part of the GI
tract?
A. Stomach
B. Jejunum 🧠 Questions 81–90: Advanced Bacteria
C. Ileum and Scenarios
D. Colon
✅ Answer: D 81. Legionella infection linked to:
75. Type of diarrhea caused by Shigella? A. Bird droppings
A. Watery B. Undercooked chicken
B. Painless C. Contaminated water systems
C. Bloody with pus D. Raw seafood
D. Steatorrhea ✅ Answer: C
✅ Answer: C 82. Best antibiotics for Legionella?
76. Cold-loving Yersinia species? A. Beta-lactams
A. Y. pestis B. Aminoglycosides
B. Y. enterocolitica C. Macrolides/fluoroquinolones
C. Y. pseudotuberculosis D. Tetracyclines
D. Y. ruckeri ✅ Answer: C
✅ Answer: B 83. Bacteria requiring cysteine to grow?
77. 3-year-old with bloody diarrhea after A. Salmonella
undercooked beef: B. Francisella tularensis
A. Campylobacter jejuni C. Pseudomonas
B. Salmonella typhi D. Neisseria
C. E. coli O157:H7 ✅ Answer: B
D. Shigella 84. “Safety pin” appearance on staining?
✅ Answer: C A. Brucella
78. Mechanism of Shiga toxin: B. Pasteurella
A. Inhibits 60S ribosome C. Yersinia pestis
 D. Campylobacter 91. Microaerophilic, spiral-shaped
✅ Answer: C GNR?
85. Campylobacter is transmitted via: A. Shigella
A. Dairy B. Campylobacter jejuni
B. Poultry C. Vibrio cholerae
C. Fecal contact D. H. influenzae
D. Ticks ✅ Answer: B
✅ Answer: B 92. Triple therapy for H. pylori includes:
86. Neonate with meningitis, GNR A. Penicillin alone
coccobacilli: B. Metronidazole + Bismuth +
A. Listeria monocytogenes Tetracycline
B. E. coli C. Cephalexin only
C. N. meningitidis D. Erythromycin only
D. H. influenzae ✅ Answer: B
✅ Answer: D 93. Gram-negative diplococci in
87. Diabetic with UTI and ammonia neutrophils?
odor: A. Chlamydia trachomatis
A. E. coli B. H. ducreyi
B. Klebsiella C. N. gonorrhoeae
C. Proteus mirabilis D. T. pallidum
D. Enterobacter ✅ Answer: C
✅ Answer: C 94. Mouse-like odor after bite infection?
88. Oxidase result for Pseudomonas? A. Francisella
A. Negative B. Pasteurella multocida
B. Weakly positive C. Brucella
C. Strongly positive D. Yersinia
D. Variable ✅ Answer: B
✅ Answer: C 95. Dysentery with seizures; nonmotile,
89. Red pigment, hospital contaminant? non-lactose fermenter?
A. Proteus A. Salmonella
B. Serratia marcescens B. Campylobacter
C. E. coli C. Shigella
D. H. aegyptius D. E. coli
✅ Answer: B ✅ Answer: C
90. Safety-pin GNR from lymph node? 96. Pink colonies on MacConkey agar
A. Tularemia indicate:
B. Brucellosis A. Non-lactose fermentation
C. Plague B. Rapid glucose fermentation
D. Melioidosis C. Lactose fermentation
✅ Answer: C D. H₂S production
✅ Answer: C
97. Bull’s-eye colonies on CIN agar?
A. Yersinia enterocolitica
🔬 Questions 91–100: Lab & Clinical B. Salmonella
Integration C. Shigella
 D. Proteus
✅ Answer: A
98. Resistance in Pseudomonas is due to:
A. Endotoxin
B. Capsule
C. Pili
D. Biofilm formation
✅ Answer: D
99. Reliable Legionella diagnostic test?
A. Ziehl-Neelsen
B. India ink
C. Urine antigen test
D. Blood culture
✅ Answer: C
100. Oxidase-positive, comma-
shaped, alkaline growth?
A. Shigella
B. Salmonella
C. Vibrio cholerae
D. E. coli
✅ Answer: C