Nokea
Which of the following is characteristic of obligate anaerobes?
- A. They require oxygen to survive
- B. They can survive in the presence or absence of oxygen
- C. They cannot tolerate oxygen
- D. They prefer low levels of oxygen
Correct Answer: C
Rationale: The correct answer is C: Obligate anaerobes cannot tolerate oxygen. They lack the enzymes needed to detoxify reactive oxygen species generated in the presence of oxygen. This makes them unable to survive in oxygen-rich environments. Choice A is incorrect because obligate anaerobes do not require oxygen to survive. Choice B is incorrect because obligate anaerobes specifically require the absence of oxygen. Choice D is incorrect because obligate anaerobes cannot even tolerate low levels of oxygen.
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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.
A centrifugate of urine sample obtained from patient with suspected renal tuberculosis was used to make a slide mount for microscopy. What method should be used to stain the slide and detect the causative agent?
- A. Zielh-Neelsen stain
- B. Loeffler stain
- C. Gram stain
- D. Aujeszky stain
Correct Answer: A
Rationale: The correct answer is A: Zielh-Neelsen stain. This stain is specifically used to detect acid-fast bacteria like Mycobacterium tuberculosis, the causative agent of renal tuberculosis. The staining process involves using carbol fuchsin to penetrate the mycolic acid layer of the bacterial cell wall, making it resistant to decolorization with acid-alcohol. This allows the red stained bacteria to be visualized under a microscope. Loeffler stain (B) is used for staining bacteria like diphtheria bacilli, Gram stain (C) is used for bacterial classification based on cell wall properties, and Aujeszky stain (D) is not a recognized staining method for detecting acid-fast bacteria.
Which bacterial structure allows for attachment to host cells?
- A. Flagella
- B. Fimbriae
- C. Capsule
- D. Endospore
Correct Answer: B
Rationale: The correct answer is B: Fimbriae. Fimbriae are hair-like appendages found on the surface of bacteria that enable attachment to host cells. This attachment is crucial for establishing infection. Flagella (A) are used for movement, not attachment. Capsules (C) provide protection and help evade the host immune system, but do not directly facilitate attachment. Endospores (D) are dormant structures for survival, not for attachment to host cells. Fimbriae specifically aid in adherence to host cells, making them the correct choice in this context.
Which of the following bacteria are unable to synthesize ATP?
- A. Chlamydia
- B. Enterococci
- C. Rickettsia
- D. Staphylococci
Correct Answer: A
Rationale: The correct answer is A: Chlamydia. Chlamydia lacks the essential enzymes for ATP synthesis and relies on host cell ATP. Enterococci, Rickettsia, and Staphylococci possess the necessary enzymes for ATP synthesis through cellular respiration. Chlamydia's inability to synthesize ATP makes it dependent on the host cell for energy production, distinguishing it from the other bacteria listed.
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.