Nokea
A patient presented with gas gangrene. Gram-positive rods producing spores and gas were isolated from a wound sample. Identify the microorganism.
- A. Clostridium perfringens
- B. Clostridium tetani
- C. Bacillus anthracis
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Clostridium perfringens. Clostridium perfringens is known to cause gas gangrene and is a Gram-positive rod that produces spores and gas in tissue infections. Clostridium tetani causes tetanus, not gas gangrene. Bacillus anthracis causes anthrax, not gas gangrene. Staphylococcus aureus is a Gram-positive cocci and does not produce spores or gas in the context of gas gangrene. Therefore, based on the characteristics of the microorganism isolated from the wound sample, Clostridium perfringens is the most likely causative agent.
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A patient with a deep tissue infection had Gram-negative rods isolated from the wound culture. The bacteria were oxidase-positive and non-lactose fermenters. What is the most likely causative agent?
- A. Pseudomonas aeruginosa
- B. Escherichia coli
- C. Klebsiella pneumoniae
- D. Shigella dysenteriae
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas aeruginosa. This is because Pseudomonas is a Gram-negative rod, oxidase-positive, and non-lactose fermenter. These characteristics are typical of Pseudomonas species.
B: Escherichia coli is a Gram-negative rod but is lactose fermenter and usually oxidase-negative.
C: Klebsiella pneumoniae is a Gram-negative rod, non-lactose fermenter, but is usually oxidase-negative.
D: Shigella dysenteriae is a Gram-negative rod, non-lactose fermenter, but is usually oxidase-negative and is more associated with causing shigellosis rather than deep tissue infections.
A woman delivered a dead child with multiple developmental defects. What protozoan disease might have caused the intrauterine death?
- A. Toxoplasmosis
- B. Leishmaniasis
- C. Malaria
- D. Amebiasis
Correct Answer: A
Rationale: The correct answer is A: Toxoplasmosis. Toxoplasmosis is a parasitic infection caused by Toxoplasma gondii, which can be transmitted from mother to fetus during pregnancy, leading to congenital toxoplasmosis. This infection can result in stillbirth, multiple developmental defects, and intrauterine death. Leishmaniasis (B), Malaria (C), and Amebiasis (D) are caused by different parasites and do not typically lead to intrauterine death or developmental defects in the fetus.
A patient with a sore throat and fever had a throat smear stained with Gram's method, revealing Gram-positive cocci in chains. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Neisseria gonorrhoeae
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes. This bacterium is known to cause sore throat and fever, commonly referred to as strep throat. Gram's stain showing Gram-positive cocci in chains is characteristic of Streptococcus species. Streptococcus pyogenes is a beta-hemolytic bacterium that forms chains and is a common cause of bacterial pharyngitis. Staphylococcus aureus (B) is a Gram-positive cocci that forms clusters, not chains. Neisseria gonorrhoeae (C) is a Gram-negative diplococcus and is not associated with sore throat. Enterococcus faecalis (D) is a Gram-positive cocci that can cause infections but is not typically associated with sore throat.
The Marburg virus was originally spread by:
- A. laboratory rats
- B. birds
- C. green monkeys
- D. wild turkeys
Correct Answer: C
Rationale: The correct answer is C: green monkeys. The Marburg virus was first identified in 1967 in Marburg and Frankfurt, Germany, after outbreaks in lab workers exposed to infected African green monkeys. These monkeys were imported from Uganda. The virus is believed to be originally endemic in certain species of African bats and is transmitted to humans through contact with infected animals. Choice A, laboratory rats, is incorrect as the virus did not originate from rats. Choice B, birds, and Choice D, wild turkeys, are also incorrect as there is no evidence linking these animals to the transmission of the Marburg virus.
For cultivation of Brucella, pure cultures should be incubated in CO2 enriched atmosphere. What type of breathing is typical for Brucella?
- A. Capnophilic
- B. Facultative anaerobic
- C. Obligate anaerobic
- D. Obligate aerobic
Correct Answer: A
Rationale: The correct answer is A: Capnophilic. Brucella requires a CO2 enriched atmosphere for cultivation, making it capnophilic. This is because Brucella is a microaerophilic bacterium that thrives in low oxygen conditions and elevated CO2 levels. Choice B (Facultative anaerobic) and D (Obligate aerobic) are incorrect as Brucella does not grow well under aerobic conditions. Choice C (Obligate anaerobic) is also incorrect as Brucella can grow in the presence of oxygen, although it prefers low oxygen environments.