A 32-year-old patient undergoing dental examination was found to have some rash-like lesions resembling secondary syphilis in the oral cavity. The patient was referred for the serological study with the purpose of diagnosis confirmation. In order to detect antibodies in the serum, living Treponema were used as diagnosticum. What serological test was performed?

Correct Answer: B

Rationale: The correct answer is B: Passive hemagglutination. In this test, red blood cells coated with Treponema antigens agglutinate in the presence of patient's serum antibodies. This indicates the presence of antibodies against Treponema, confirming the diagnosis. A: Immobilization test uses live Treponema to detect specific antibodies, but it is not commonly used for syphilis diagnosis. C: Precipitation test is not commonly used for syphilis diagnosis. D: Complement binding test is not specific for syphilis and is used more for autoimmune diseases. Therefore, passive hemagglutination is the most appropriate serological test in this case due to its specificity and relevance to the presentation of the patient.

Correct Answer: B

Rationale: Facultative anaerobes can switch between aerobic and anaerobic metabolism based on oxygen availability. This flexibility enables them to grow in both oxygen-rich and oxygen-poor environments, making choice B correct. Choice A is incorrect because facultative anaerobes do not require oxygen for survival. Choice C is incorrect as obligate anaerobes cannot grow in the presence of oxygen. Choice D is incorrect because obligate anaerobes cannot tolerate any amount of oxygen.

Correct Answer: A

Rationale: The correct answer is A: Streptomycin. Streptomycin is an aminoglycoside antibiotic used to treat tuberculosis that can cause hearing loss as a side effect. It is known to damage the cochlear and vestibular organs in the inner ear. The other choices, B: Isoniazid, C: Rifampicin, and D: Ethionamide, are not associated with causing hearing deterioration as a side effect. Isoniazid can rarely cause peripheral neuropathy, Rifampicin can lead to hepatotoxicity, and Ethionamide may cause gastrointestinal disturbances, but none of these drugs are known to specifically cause hearing loss.

Correct Answer: B

Rationale: Step-by-step rationale: 1. Monotrichous means having a single flagellum at one end. 2. The term "polar" indicates that the flagellum is located at one end of the bacterium. 3. Therefore, bacteria with a single polar flagellum are referred to as monotrichous. 4. Choice A is a typo, as it is the same as the correct answer B. Summary: - Choice A is a typo, as it duplicates the correct answer. - Choice C, amphitrichous, refers to bacteria with a flagellum at each end. - Choice D, peritrichous, describes bacteria with flagella distributed over the entire surface.

Correct Answer: A

Rationale: The correct answer is A: Staphylococcus aureus. 1. Gram-positive cocci in clusters suggest staphylococci. 2. Catalase-positive indicates staphylococci since streptococci are catalase-negative. 3. Coagulase-positive further confirms Staphylococcus aureus, distinguishing it from other staphylococci. Summary: B is incorrect as Streptococcus pyogenes is catalase-negative. C is incorrect as Micrococcus luteus is catalase-negative and coagulase-negative. D is incorrect as Enterococcus faecalis is catalase-negative and coagulase-negative.

Correct Answer: D

Rationale: The correct answer is D because hospital-acquired infections can be caused by a variety of microorganisms, including opportunistic pathogens and obligate pathogens such as bacteria or viruses. Opportunistic microorganisms take advantage of weakened immune systems in hospital patients, while obligate pathogens are capable of causing infections in healthy individuals. Therefore, all the choices are correct in this context as they represent potential etiological causes of hospital-acquired infections.

Correct Answer: C

Rationale: The correct answer is C because both Clostridium botulinum and Bacillus anthracis are capable of forming spores to survive in extreme conditions. Clostridium botulinum is known for causing botulism and produces highly heat-resistant spores, while Bacillus anthracis is the causative agent of anthrax and also forms spores. Choice A is incorrect because only Clostridium botulinum is mentioned, not Bacillus anthracis. Choice B is incorrect because only Bacillus anthracis is mentioned, not Clostridium botulinum. Choice D is incorrect as it states that none of the bacteria can form spores, which is false based on the characteristics of Clostridium botulinum and Bacillus anthracis.

Correct Answer: A

Rationale: Subcutaneous mycoses are fungal infections that affect the skin, subcutaneous tissues, and bones. The correct answer is A: tropics, as these infections are more commonly found in warm and humid regions. Fungi that cause subcutaneous mycoses thrive in tropical climates due to the favorable conditions for their growth and transmission. Choices B, C, and D are incorrect because deserts (B) have dry conditions not conducive to fungal growth, forests of the Northern Hemisphere (C) have varying climates that may not support the specific fungi causing subcutaneous mycoses, and the Rocky Mountains (D) are not typically associated with the high humidity required for these infections.

Correct Answer: C

Rationale: The correct answer is C: Salmonella typhi. Typhoid fever is caused by the bacterium Salmonella typhi, specifically transmitted through contaminated food and water. Shigella dysenteriae causes bacillary dysentery, Vibrio cholerae causes cholera, and Escherichia coli can cause various gastrointestinal illnesses, but not typhoid fever. Identifying the causative agent is crucial for effective treatment and prevention strategies.