1. Which organism is responsible for causing most cases of bacterial pneumonia in adults?
A) Streptococcus pneumoniae
B) Haemophilus influenzae
C) Staphylococcus aureus
D) Legionella pneumophila
2. A patient presents with watery diarrhea and abdominal cramps after consuming contaminated food. Which pathogen is the most likely cause?
A) Escherichia coli (E. coli)
B) Salmonella enterica
C) Clostridium difficile
D) Campylobacter jejuni
3. A young sexually active female presents with vaginal discharge and itching. A wet mount microscopy reveals clue cells. Which microorganism is responsible for this condition?
A) Candida albicans
B) Trichomonas vaginalis
C) Neisseria gonorrhoeae
D) Gardnerella vaginalis
4. Which viral pathogen is responsible for causing mononucleosis, commonly known as the “kissing disease”?
A) Epstein-Barr virus (EBV)
B) Cytomegalovirus (CMV)
C) Herpes simplex virus (HSV)
D) Human papillomavirus (HPV)
5. A patient with a history of HIV infection presents with a fungal lung infection. The fungal organism is a dimorphic fungus, and a chest X-ray shows cavitary lesions. Which fungus is most likely responsible?
A) Aspergillus fumigatus
B) Cryptococcus neoformans
C) Histoplasma capsulatum
D) Candida albicans
6. Which bacteria are the causative agents of Lyme disease?
A) Borrelia burgdorferi
B) Treponema pallidum
C) Leptospira interrogans
D) Rickettsia rickettsii
7. A patient with a recent history of travel to Central America presents with fever, headache, and a maculopapular rash spreading from the trunk to the extremities. Which virus is the likely cause?
A) Dengue virus
B) Chikungunya virus
C) Yellow fever virus
D) Zika virus
8. Which microorganism is responsible for causing gas gangrene?
A) Clostridium perfringens
B) Streptococcus pyogenes
C) Staphylococcus aureus
D) Escherichia coli
9. A patient with a history of chronic granulomatous disease presents with recurrent infections involving catalase-positive organisms. Which enzyme is defective in this condition?
A) NADPH oxidase
B) Catalase
C) Superoxide dismutase
D) Glucose-6-phosphate dehydrogenase
10. A pregnant woman presents with flu-like symptoms and a rash. Laboratory testing reveals a positive IgM antibody for rubella. What is the primary concern in this case?
A) Fetal malformations
B) Maternal respiratory distress
C) Maternal heart failure
D) Risk of neonatal sepsis
11. A young child presents with high fever, a “strawberry tongue,” and a rash starting on the face and spreading to the trunk. Which bacterium is the most likely cause?
A) Streptococcus pyogenes
B) Staphylococcus aureus
C) Neisseria meningitidis
D) Haemophilus influenzae
12. A patient with a history of splenectomy presents with fever, headache, and confusion after a hiking trip. Examination of a blood smear reveals intraerythrocytic ring forms. Which protozoan parasite is responsible?
A) Plasmodium falciparum
B) Trypanosoma cruzi
C) Leishmania donovani
D) Babesia microti
13. Which virus is responsible for causing hand-foot-and-mouth disease, characterized by vesicular lesions on the hands, feet, and oral mucosa?
A) Coxsackievirus A16
B) Herpes simplex virus (HSV)
C) Human papillomavirus (HPV)
D) Varicella-zoster virus (VZV)
14. A patient with a history of bird exposure presents with pneumonia and gastrointestinal symptoms. Which fungal organism is most likely responsible?
A) Aspergillus fumigatus
B) Candida albicans
C) Cryptococcus neoformans
D) Histoplasma capsulatum
15. Which bacterial pathogen is responsible for causing the majority of community-acquired urinary tract infections (UTIs) in otherwise healthy women?
A) Escherichia coli (E. coli)
B) Klebsiella pneumoniae
C) Enterococcus faecalis
D) Proteus mirabilis
16. A patient with a history of HIV infection presents with chronic diarrhea and a low CD4 count. Stool examination reveals acid-fast bacilli. Which microorganism is most likely responsible?
A) Mycobacterium tuberculosis
B) Mycobacterium leprae
C) Mycobacterium avium complex
D) Mycobacterium bovis
17. A patient presents with severe respiratory distress and a high fever. Chest X-ray shows bilateral diffuse infiltrates. Which viral pathogen is most likely responsible?
A) Respiratory syncytial virus (RSV)
B) Influenza virus
C) Parainfluenza virus
D) Adenovirus
18. Which organism is responsible for causing bacterial vaginosis, characterized by a thin, grayish-white discharge with a fishy odor?
A) Candida albicans
B) Trichomonas vaginalis
C) Gardnerella vaginalis
D) Chlamydia trachomatis
19. A patient presents with a purulent skin infection with “honey-colored” crusts. Which bacterium is most likely responsible?
A) Staphylococcus aureus
B) Streptococcus pyogenes
C) Clostridium perfringens
D) Corynebacterium diphtheriae
20. Which virus is responsible for causing infectious mononucleosis in adolescents and young adults?
A) Epstein-Barr virus (EBV)
B) Cytomegalovirus (CMV)
C) Herpes simplex virus (HSV)
D) Human immunodeficiency virus (HIV)
21. A patient presents with fever, headache, and a maculopapular rash starting on the face and spreading to the trunk and extremities. The rash blanches with pressure. Which virus is the most likely cause?
A) Rubella virus
B) Measles virus
C) Varicella-zoster virus (VZV)
D) Herpes simplex virus (HSV)
22. A patient with a history of intravenous drug use presents with fever, murmur, and embolic phenomenon. Which microorganism is most likely responsible?
A) Staphylococcus aureus
B) Streptococcus pneumoniae
C) Enterococcus faecalis
D) Neisseria gonorrhoeae
23. Which bacterial pathogen is responsible for causing syphilis?
A) Treponema pallidum
B) Neisseria meningitidis
C) Chlamydia trachomatis
D) Haemophilus ducreyi
24. A patient with a history of liver transplantation presents with a rapidly progressive fungal infection. The fungal organism produces thick-walled spherical yeast cells. Which organism is most likely responsible?
A) Candida albicans
B) Cryptococcus neoformans
C) Aspergillus fumigatus
D) Mucorales spp.
25. Which virus is responsible for causing cold sores (oral herpes)?
A) Herpes simplex virus type 1 (HSV-1)
B) Herpes simplex virus type 2 (HSV-2)
C) Varicella-zoster virus (VZV)
D) Human papillomavirus (HPV)
26. A patient with a history of animal exposure presents with fever, headache, and nuchal rigidity. Examination of cerebrospinal fluid reveals pleocytosis and Gram-negative coccobacilli. Which bacterium is the most likely cause?
A) Escherichia coli (E. coli)
B) Streptococcus pneumoniae
C) Neisseria meningitidis
D) Listeria monocytogenes
27. Which fungal organism is responsible for causing oral thrush, characterized by creamy white plaques on the oral mucosa that can be scraped off?
A) Candida albicans
B) Cryptococcus neoformans
C) Aspergillus fumigatus
D) Histoplasma capsulatum
28. A patient presents with severe diarrhea, vomiting, and dehydration after a camping trip. Which bacterial pathogen is most likely responsible?
A) Escherichia coli (E. coli) O157:H7
B) Salmonella enterica
C) Vibrio cholerae
D) Campylobacter jejuni
29. Which bacterial pathogen is responsible for causing the majority of hospital-acquired urinary tract infections (UTIs)?
A) Escherichia coli (E. coli)
B) Klebsiella pneumoniae
C) Enterococcus faecalis
D) Pseudomonas aeruginosa
30. A patient presents with fever, headache, and a maculopapular rash that starts on the face and spreads to the trunk and extremities. The rash does not blanch with pressure. Which virus is the most likely cause?
A) Rubella virus
B) Measles virus
C) Varicella-zoster virus (VZV)
D) Herpes simplex virus (HSV)
31. Which protozoan parasite is responsible for causing severe watery diarrhea in immunocompromised
patients, often acquired from contaminated water sources?
A) Giardia lamblia
B) Entamoeba histolytica
C) Cryptosporidium parvum
D) Toxoplasma gondii
32. A patient presents with fever, cough, and hemoptysis. Chest X-ray reveals cavitary lesions with a “ball-in-cup” appearance. Which bacterial pathogen is most likely responsible?
A) Mycobacterium tuberculosis
B) Streptococcus pneumoniae
C) Klebsiella pneumoniae
D) Pseudomonas aeruginosa
33. Which bacterium is responsible for causing urinary tract infections (UTIs) in sexually active young females?
A) Escherichia coli (E. coli)
B) Klebsiella pneumoniae
C) Enterococcus faecalis
D) Proteus mirabilis
34. A patient presents with fever, cough, and difficulty breathing. Chest X-ray reveals patchy interstitial infiltrates. Which viral pathogen is most likely responsible?
A) Respiratory syncytial virus (RSV)
B) Influenza virus
C) Parainfluenza virus
D) Adenovirus
35. Which organism is responsible for causing bacterial vaginosis, characterized by a thin, grayish-white discharge with a fishy odor?
A) Candida albicans
B) Trichomonas vaginalis
C) Gardnerella vaginalis
D) Chlamydia trachomatis
36. A patient presents with purulent skin lesions and swollen lymph nodes. Gram stain shows gram-positive cocci in clusters. Which bacterium is most likely responsible?
A) Staphylococcus aureus
B) Streptococcus pyogenes
C) Clostridium perfringens
D) Corynebacterium diphtheriae
37. Which virus is responsible for causing infectious mononucleosis in adolescents and young adults?
A) Epstein-Barr virus (EBV)
B) Cytomegalovirus (CMV)
C) Herpes simplex virus (HSV)
D) Human immunodeficiency virus (HIV)
38. A patient presents with fever, headache, and a maculopapular rash starting on the face and spreading to the trunk and extremities. The rash blanches with pressure. Which virus is the most likely cause?
A) Rubella virus
B) Measles virus
C) Varicella-zoster virus (VZV)
D) Herpes simplex virus (HSV)
39. A patient with a history of intravenous drug use presents with fever, murmur, and embolic phenomenon. Which microorganism is most likely responsible?
A) Staphylococcus aureus
B) Streptococcus pneumoniae
C) Enterococcus faecalis
D) Neisseria gonorrhoeae
40. Which bacterial pathogen is responsible for causing syphilis?
A) Treponema pallidum
B) Neisseria meningitidis
C) Chlamydia trachomatis
D) Haemophilus ducreyi
41. A patient with a history of liver transplantation presents with a rapidly progressive fungal infection. The fungal organism produces thick-walled spherical yeast cells. Which organism is most likely responsible?
A) Candida albicans
B) Cryptococcus neoformans
C) Aspergillus fumigatus
D) Mucorales spp.
42. Which virus is responsible for causing cold sores (oral herpes)?
A) Herpes simplex virus type 1 (HSV-1)
B) Herpes simplex virus type 2 (HSV-2)
C) Varicella-zoster virus (VZV)
D) Human papillomavirus (HPV)
43. A patient with a history of animal exposure presents with fever, headache, and nuchal rigidity. Examination of cerebrospinal fluid reveals pleocytosis and Gram-negative coccobacilli. Which bacterium is the most likely cause?
A) Escherichia coli (E. coli)
B) Streptococcus pneumoniae
C) Neisseria meningitidis
D) Listeria monocytogenes
44. Which fungal organism is responsible for causing oral thrush, characterized by creamy white plaques on the oral mucosa that can be scraped off?
A) Candida albicans
B) Cryptococcus neoformans
C) Aspergillus fumigatus
D) Histoplasma capsulatum
45. A patient presents with severe diarrhea, vomiting, and dehydration after a camping trip. Which bacterial pathogen is most likely responsible?
A) Escherichia coli (E. coli) O157:H7
B) Salmonella enterica
C) Vibrio cholerae
D) Campylobacter jejuni
46. Which bacterial pathogen is responsible for causing the majority of hospital-acquired urinary tract infections (UTIs)?
A) Escherichia coli (E. coli)
B) Klebsiella pneumoniae
C) Enterococcus faecalis
D) Pseudomonas aeruginosa
47. A patient presents with fever, headache, and a maculopapular rash that starts on the face and spreads to the trunk and extremities. The rash does not blanch with pressure. Which virus is the most likely cause?
A) Rubella virus
B) Measles virus
C) Varicella-zoster virus (VZV)
D) Herpes simplex virus (HSV)
48. Which protozoan parasite is responsible for causing severe watery diarrhea in immunocompromised patients, often acquired from contaminated water sources?
A) Giardia lamblia
B) Entamoeba histolytica
C) Cryptosporidium parvum
D) Toxoplasma gondii
49. A patient presents with fever, cough, and hemoptysis. Chest X-ray reveals cavitary lesions with a “ball-in-cup” appearance. Which bacterial pathogen is most likely responsible?
A) Mycobacterium tuberculosis
B) Streptococcus pneumoniae
C) Klebsiella pneumoniae
D) Pseudomonas aeruginosa
50. Which bacterium is responsible for causing urinary tract infections (UTIs) in sexually active young females?
A) Escherichia coli (E. coli)
B) Klebsiella pneumoniae
C) Enterococcus faecalis
D) Proteus mirabilis