Here’s the microbiology case studies with answers.
- Case Study: A patient presents with fever, chills, and a history of camping near a freshwater lake. A blood smear reveals intraerythrocytic parasites. What is the most likely causative agent?
a) Plasmodium falciparum
b) Trypanosoma cruzi
c) Toxoplasma gondii
d) Giardia lamblia Answer: a) Plasmodium falciparum - Case Study: A patient experiences severe watery diarrhea after consuming contaminated food. Stool samples show motile, comma-shaped bacteria. Which pathogen is responsible?
a) Salmonella enterica
b) Escherichia coli (E. coli)
c) Vibrio cholerae
d) Clostridium difficile Answer: c) Vibrio cholerae
- Case Study: A sexually active individual presents with painful genital ulcers. Dark-field microscopy reveals spiral-shaped bacteria. What is the likely causative agent?
a) Treponema pallidum
b) Neisseria gonorrhoeae
c) Chlamydia trachomatis
d) Herpes simplex virus Answer: a) Treponema pallidum - Case Study: A child develops a fever and a “strawberry tongue.” Examination shows enlarged lymph nodes. What is the most likely diagnosis?
a) Streptococcus pneumoniae
b) Streptococcus pyogenes
c) Streptococcus mutans
d) Streptococcus agalactiae Answer: b) Streptococcus pyogenes - Case Study: A patient with AIDS presents with a lung infection characterized by yeast-like cells in lung tissue. Which fungus is the probable causative agent?
a) Candida albicans
b) Aspergillus fumigatus
c) Cryptococcus neoformans
d) Histoplasma capsulatum Answer: c) Cryptococcus neoformans
- Case Study: A patient presents with a high fever, joint pain, and a recent history of travel to a tropical region. Lab tests reveal thrombocytopenia and leukopenia. What is the most likely causative agent?
a) Dengue virus
b) Influenza virus
c) Zika virus
d) Epstein-Barr virus Answer: a) Dengue virus - Case Study: A patient develops a skin infection characterized by red, raised, and painful nodules with central pustules. What is the most likely causative bacterium?
a) Staphylococcus aureus
b) Streptococcus pneumoniae
c) Clostridium perfringens
d) Mycobacterium tuberculosis Answer: a) Staphylococcus aureus - Case Study: A patient presents with diarrhea containing blood and mucus. Stool samples reveal trophozoites with ingested red blood cells. What is the probable causative agent?
a) Entamoeba histolytica
b) Giardia lamblia
c) Cryptosporidium parvum
d) Trichomonas vaginalis Answer: a) Entamoeba histolytica - Case Study: A healthcare worker develops a respiratory infection with a “fried-egg” appearance on culture. What is the likely pathogen?
a) Mycoplasma pneumoniae
b) Legionella pneumophila
c) Chlamydophila pneumoniae
d) Pneumocystis jirovecii Answer: b) Legionella pneumophila - Case Study: A patient with a history of animal contact presents with fever, night sweats, and weight loss. Acid-fast bacilli are seen in sputum samples. What is the likely diagnosis?
a) Tuberculosis (Mycobacterium tuberculosis)
b) Leprosy (Mycobacterium leprae)
c) Pertussis (Bordetella pertussis)
d) Tetanus (Clostridium tetani) Answer: a) Tuberculosis (Mycobacterium tuberculosis) - Case Study: A patient develops a urinary tract infection. Urine culture reveals pink colonies on MacConkey agar. What is the likely causative bacterium?
a) Escherichia coli
b) Klebsiella pneumoniae
c) Pseudomonas aeruginosa
d) Enterococcus faecalis Answer: a) Escherichia coli - Case Study: A patient presents with a pruritic rash and clusters of fluid-filled vesicles on the skin. What virus is most likely responsible?
a) Varicella-Zoster virus
b) Measles virus
c) Rubella virus
d) Human papillomavirus Answer: a) Varicella-Zoster virus - Case Study: A patient presents with foul-smelling, frothy diarrhea and abdominal cramps. Microscopy reveals motile, pear-shaped trophozoites. What is the likely causative agent?
a) Entamoeba histolytica
b) Giardia lamblia
c) Trichomonas vaginalis
d) Cryptosporidium parvum Answer: b) Giardia lamblia - Case Study: A patient presents with a high fever, headache, and muscle pain. Recent travel history includes a camping trip in the woods. What is the likely causative agent?
a) Borrelia burgdorferi
b) Rickettsia rickettsii
c) Anaplasma phagocytophilum
d) Bartonella henselae Answer: a) Borrelia burgdorferi - Case Study: A patient presents with a wound infection after a dog bite. What bacterium is often associated with such infections?
a) Streptococcus pneumoniae
b) Staphylococcus epidermidis
c) Pasteurella multocida
d) Escherichia coli Answer: c) Pasteurella multocida
- Case Study: A neonate presents with severe pneumonia and conjunctivitis. What is the likely causative agent?
a) Chlamydia trachomatis
b) Neisseria gonorrhoeae
c) Mycoplasma pneumoniae
d) Streptococcus pneumoniae Answer: b) Neisseria gonorrhoeae - Case Study: A patient develops a skin abscess with central necrosis. Gram stain shows gram-positive cocci in clusters. What is the likely bacterium?
a) Streptococcus pyogenes
b) Staphylococcus aureus
c) Clostridium perfringens
d) Escherichia coli Answer: b) Staphylococcus aureus - Case Study: A patient presents with diarrhea after eating undercooked poultry. Stool samples reveal gram-negative, spiral-shaped bacteria. What is the likely causative agent?
a) Salmonella enterica
b) Campylobacter jejuni
c) Escherichia coli (E. coli)
d) Shigella flexneri Answer: b) Campylobacter jejuni - Case Study: A patient presents with meningitis symptoms, and cerebrospinal fluid analysis shows gram-negative diplococci. What is the likely pathogen?
a) Streptococcus pneumoniae
b) Neisseria meningitidis
c) Haemophilus influenzae
d) Listeria monocytogenes Answer: b) Neisseria meningitidis - Case Study: A patient with a history of exposure to bat guano develops a severe respiratory illness. Which fungus is the probable causative agent?
a) Aspergillus fumigatus
b) Histoplasma capsulatum
c) Cryptococcus neoformans
d) Candida albicans Answer: b) Histoplasma capsulatum - Case Study: A patient presents with oral thrush and esophagitis. Which organism is often responsible for this condition in immunocompromised individuals?
a) Candida albicans
b) Aspergillus fumigatus
c) Pneumocystis jirovecii
d) Cryptococcus neoformans Answer: a) Candida albicans - Case Study: A patient presents with fever, jaundice, and hepatomegaly. Blood smears show intraerythrocytic parasites with a “ring form.” What is the likely causative agent?
a) Plasmodium vivax
b) Babesia microti
c) Toxoplasma gondii - Case Study: A patient presents with a productive cough, night sweats, and weight loss. Chest X-rays reveal cavitary lesions in the lungs. What is the likely diagnosis?
a) Tuberculosis (Mycobacterium tuberculosis)
b) Influenza (Influenza virus)
c) Aspergillosis (Aspergillus species)
d) Histoplasmosis (Histoplasma capsulatum) Answer: a) Tuberculosis (Mycobacterium tuberculosis) - Case Study: A patient develops a foodborne illness with diarrhea and abdominal cramps after consuming contaminated poultry. Which bacterium is often responsible?
a) Clostridium difficile
b) Campylobacter jejuni
c) Escherichia coli (E. coli)
d) Salmonella enterica Answer: d) Salmonella enterica - Case Study: A patient with a history of cystic fibrosis presents with a chronic respiratory infection. What bacterium is commonly associated with these infections?
a) Pseudomonas aeruginosa
b) Streptococcus pneumoniae
c) Mycoplasma pneumoniae
d) Haemophilus influenzae Answer: a) Pseudomonas aeruginosa - Case Study: A patient develops a urinary tract infection. Urine culture reveals small, gram-negative rods. What is the likely causative bacterium?
a) Escherichia coli
b) Klebsiella pneumoniae
c) Proteus mirabilis
d) Enterococcus faecalis Answer: c) Proteus mirabilis - Case Study: A patient presents with a high fever, severe headache, and a petechial rash. What is the likely causative agent?
a) Staphylococcus aureus
b) Streptococcus pyogenes
c) Rickettsia rickettsii
d) Neisseria meningitidis Answer: c) Rickettsia rickettsii - Case Study: A patient with a compromised immune system presents with a severe lung infection. Chest X-rays show diffuse, bilateral infiltrates. What is the likely causative agent?
a) Mycobacterium tuberculosis
b) Pneumocystis jirovecii
c) Streptococcus pneumoniae
d) Chlamydia pneumoniae Answer: b) Pneumocystis jirovecii - Case Study: A patient presents with a cutaneous lesion at the site of a cat scratch. What bacterium is commonly associated with this condition?
a) Staphylococcus aureus
b) Streptococcus pyogenes
c) Bartonella henselae
d) Francisella tularensis Answer: c) Bartonella henselae - Case Study: A patient presents with a severe respiratory infection and a history of exposure to bird droppings. What fungus is commonly associated with this condition?
a) Candida albicans
b) Histoplasma capsulatum
c) Aspergillus fumigatus
d) Cryptococcus neoformans Answer: b) Histoplasma capsulatum - Case Study: A patient presents with severe watery diarrhea after a recent antibiotic treatment. Stool samples reveal the presence of gram-negative, rod-shaped bacteria. What is the likely causative agent?
a) Clostridium difficile
b) Salmonella enterica
c) Escherichia coli (E. coli)
d) Campylobacter jejuni Answer: a) Clostridium difficile - Case Study: A patient presents with a high fever, headache, and muscle pain. Recent travel history includes exposure to ticks. What is the likely causative agent?
a) Borrelia burgdorferi
b) Rickettsia rickettsii
c) Anaplasma phagocytophilum
d) Babesia microti Answer: a) Borrelia burgdorferi - Case Study: A patient presents with severe diarrhea, dehydration, and electrolyte imbalances. Stool samples reveal comma-shaped, gram-negative bacteria. What is the likely causative agent?
a) Vibrio cholerae
b) Salmonella enterica
c) Campylobacter jejuni
d) Shigella flexneri Answer: a) Vibrio cholerae - Case Study: A patient presents with a respiratory infection characterized by a barking cough and inspiratory stridor. What is the likely causative agent?
a) Influenza virus
b) Bordetella pertussis
c) Respiratory syncytial virus
d) Streptococcus pneumoniae Answer: b) Bordetella pertussis - Case Study: A patient with a compromised immune system develops a fungal infection characterized by septate hyphae on histopathology. What is the likely causative fungus?
a) Candida albicans
b) Aspergillus fumigatus
c) Cryptococcus neoformans
d) Histoplasma capsulatum Answer: b) Aspergillus fumigatus