Q. A 28-year-old woman presents with a sore throat and swollen lymph nodes. A rapid strep test is positive. What is the most likely causative agent?
A.Streptococcus pyogenes
B.Streptococcus pneumoniae
C.Haemophilus influenzae
D.Corynebacterium diphtheriae
Solution
Streptococcus pyogenes is the most common cause of pharyngitis and is detected by rapid strep tests.
Correct Answer: A — Streptococcus pyogenes
Q. A 30-year-old woman develops a urinary tract infection. A urine culture shows the presence of a gram-negative bacillus. Which organism is the most common cause of such infections?
A.Escherichia coli
B.Proteus mirabilis
C.Enterococcus faecalis
D.Klebsiella pneumoniae
Solution
Escherichia coli is the most common cause of urinary tract infections.
Correct Answer: A — Escherichia coli
Q. A 45-year-old man presents with fever, cough, and chest pain. A chest X-ray shows a cavitary lesion in the right upper lobe. Which microorganism is most likely responsible for this condition?
A.Streptococcus pneumoniae
B.Mycobacterium tuberculosis
C.Klebsiella pneumoniae
D.Legionella pneumophila
Solution
The cavitary lesion in the right upper lobe is characteristic of pulmonary tuberculosis, which is caused by Mycobacterium tuberculosis.
Correct Answer: B — Mycobacterium tuberculosis
Q. A 50-year-old man presents with fever, night sweats, and weight loss. A biopsy of a lymph node reveals granulomas. Which infectious agent is most likely responsible?
A.Histoplasma capsulatum
B.Mycobacterium tuberculosis
C.Coccidioides immitis
D.Brucella spp.
Solution
Granulomas in the lymph nodes are characteristic of tuberculosis, which is caused by Mycobacterium tuberculosis.
Correct Answer: B — Mycobacterium tuberculosis
Q. A child is brought to the clinic with a rash, fever, and cough. The physician suspects measles. Which vaccine could have prevented this disease?
A.Inactivated polio vaccine
B.MMR vaccine
C.Hepatitis B vaccine
D.Diphtheria-tetanus-pertussis vaccine
Solution
The MMR vaccine (measles, mumps, rubella) is effective in preventing measles.
Correct Answer: B — MMR vaccine
Q. A laboratory technician is exposed to a needle stick injury from a patient with hepatitis B. What is the most appropriate post-exposure prophylaxis?
A.Hepatitis B vaccine
B.Hepatitis A vaccine
C.Intravenous immunoglobulin
D.No treatment necessary
Solution
Post-exposure prophylaxis for hepatitis B includes administering the hepatitis B vaccine.
Correct Answer: A — Hepatitis B vaccine
Q. A patient presents with a sudden onset of high fever, chills, and a petechial rash. Blood cultures reveal Neisseria meningitidis. What is the most effective preventive measure?
A.Antibiotic prophylaxis
B.Meningococcal vaccine
C.Isolation of the patient
D.Intravenous immunoglobulin
Solution
The meningococcal vaccine is the most effective preventive measure against Neisseria meningitidis infection.
Correct Answer: B — Meningococcal vaccine
Q. A patient presents with severe diarrhea and dehydration. Stool culture reveals the presence of a toxin-producing organism. Which organism is most likely responsible?
A.Escherichia coli
B.Clostridium difficile
C.Salmonella enterica
D.Vibrio cholerae
Solution
Clostridium difficile is known for causing antibiotic-associated diarrhea and produces toxins that lead to severe gastrointestinal symptoms.
Correct Answer: B — Clostridium difficile
Q. A patient with a history of HIV presents with oral thrush and esophageal pain. What is the most likely causative organism?
A.Candida albicans
B.Aspergillus fumigatus
C.Cryptococcus neoformans
D.Histoplasma capsulatum
Solution
Oral thrush in an immunocompromised patient is most commonly caused by Candida albicans.
Correct Answer: A — Candida albicans
Q. A patient with a history of travel to tropical regions presents with fever, jaundice, and abdominal pain. Which virus is most likely responsible for these symptoms?
A.Hepatitis A virus
B.Hepatitis B virus
C.Dengue virus
D.Yellow fever virus
Solution
Yellow fever virus is endemic in tropical regions and can cause fever, jaundice, and abdominal pain.
