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A patient with a deep tissue infection had a wound culture revealing Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-negative. What is the most likely causative agent?
- A. Staphylococcus epidermidis
- B. Staphylococcus aureus
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus epidermidis. The presence of Gram-positive cocci in clusters that are catalase-positive and coagulase-negative points towards coagulase-negative staphylococci like Staphylococcus epidermidis. Staphylococcus aureus is catalase-positive and coagulase-positive. Streptococcus pyogenes is catalase-negative. Enterococcus faecalis is catalase-negative and not typically seen in clusters. Therefore, the most likely causative agent in this scenario is Staphylococcus epidermidis.
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The Staphylococcus aureus toxin, which can cause scalded skin syndrome (SSS), is:
- A. hemolysis
- B. enterotoxin
- C. leucocidin
- D. epidermolytic toxin
Correct Answer: D
Rationale: The correct answer is D: epidermolytic toxin. This toxin specifically targets the epidermis, leading to exfoliation seen in scalded skin syndrome (SSS). Hemolysis (A) refers to the destruction of red blood cells, not relevant to SSS. Enterotoxins (B) cause food poisoning, not SSS. Leucocidins (C) target white blood cells, not pertinent to SSS. Therefore, the epidermolytic toxin (D) is the correct choice for causing SSS.
A bacteriological laboratory received sputum sample of a patient suffering from tuberculosis. Bacterioscopic examination of smears and detection of tuberculosis bacillus can be realized by one of enrichment methods that involves processing of sputum only with solution of caustic soda. What is this method called?
- A. Homogenization
- B. Inactivation
- C. Flotation
- D. Filtration
Correct Answer: B
Rationale: The correct answer is B: Inactivation. In this method, the sputum sample is processed with a solution of caustic soda, which helps to kill any contaminants present and preserve the tuberculosis bacillus for microscopic examination. This step is crucial in ensuring accurate detection of the bacillus.
A: Homogenization involves breaking down the sample to make it uniform, but it does not necessarily involve using caustic soda for inactivation.
C: Flotation is a method used to separate different components based on their density and is not specific to inactivating tuberculosis bacillus.
D: Filtration involves passing a sample through a filter to separate particles based on size and is not related to inactivating the tuberculosis bacillus.
An inflammatory disease that can develop as a complication following a group A streptococcal infection is:
- A. endocarditis
- B. rheumatic fever
- C. nephritis
- D. cytomegalovirus
Correct Answer: B
Rationale: The correct answer is B: rheumatic fever. Rheumatic fever is an inflammatory disease that can occur as a complication following a group A streptococcal infection. This is known as a post-streptococcal complication. It typically affects the heart, joints, skin, and brain. Endocarditis (choice A) is also a complication of streptococcal infections, but it is an infection of the heart valves, not an inflammatory disease like rheumatic fever. Nephritis (choice C) is inflammation of the kidneys and is not directly related to streptococcal infections. Cytomegalovirus (choice D) is a different viral infection and is not associated with streptococcal infections.
After the second abortion a 23 year old woman has been diagnosed with toxoplasmosis. Which drug should be used for toxoplasmosis treatment?
- A. Co-trimoxazole
- B. Itraconazole
- C. Mebendazole
- D. Azidothimidine
Correct Answer: A
Rationale: The correct answer is A: Co-trimoxazole. This drug combination is the first-line treatment for toxoplasmosis due to its efficacy against Toxoplasma gondii. Co-trimoxazole consists of sulfamethoxazole and trimethoprim, which work synergistically to inhibit bacterial and protozoal folate synthesis, effectively treating toxoplasmosis.
B: Itraconazole is an antifungal medication and not effective against toxoplasmosis.
C: Mebendazole is an anthelmintic drug used for treating parasitic worm infections, not toxoplasmosis.
D: Azidothimidine, also known as AZT, is used for treating HIV, not toxoplasmosis.
Which of the following diseases is transmitted by the fecal–oral route?
- A. Ehrlichiosis
- B. Peptic ulcer
- C. Lyme disease
- D. Tularemia
Correct Answer: B
Rationale: The correct answer is B: Peptic ulcer. Peptic ulcers are commonly caused by Helicobacter pylori bacteria, which can be transmitted through the fecal-oral route. This means that the bacteria from infected feces can be ingested through contaminated food or water, leading to the development of peptic ulcers in the gastrointestinal tract.
Incorrect choices:
A: Ehrlichiosis - Ehrlichiosis is a tick-borne disease transmitted through the bite of an infected tick, not through the fecal-oral route.
C: Lyme disease - Lyme disease is also transmitted through the bite of an infected tick, specifically the black-legged tick.
D: Tularemia - Tularemia is a bacterial disease typically transmitted through insect bites, handling of infected animals, or ingestion of contaminated water, not through the fecal-oral route.