All of the following areas of the human body contain normal flora except:

Correct Answer: A

Rationale: The correct answer is A: Peritoneum. Normal flora refers to the microorganisms that naturally inhabit the human body without causing harm. The peritoneum is a sterile area, so it does not harbor normal flora. The urethra, vagina, and mouth all have normal flora due to their moist and warm environments, which provide an ideal habitat for microorganisms to thrive. The peritoneum, being a sterile cavity that houses organs like the stomach and intestines, does not have a natural microbial population like the other areas mentioned. Therefore, it does not contain normal flora.

Correct Answer: B

Rationale: The correct answer is B: Outer membrane with lipopolysaccharides. Gram-negative bacteria have an outer membrane containing lipopolysaccharides (LPS), which are important in pathogenesis and immune response. This feature is unique to Gram-negative bacteria, distinguishing them from Gram-positive bacteria (choice A). Teichoic acids (choice C) are found in the cell walls of Gram-positive bacteria, not Gram-negative. The statement in choice D, absence of a cell wall, is incorrect as all bacteria have a cell wall, although the composition may vary between Gram-negative and Gram-positive bacteria.

Correct Answer: B

Rationale: Step 1: Adenoviruses are known to have icosahedral capsids, not helical. Step 2: Helical capsids are typically found in viruses like tobacco mosaic virus. Step 3: Therefore, the statement that adenoviruses have helical capsids is FALSE. Summary: A is incorrect as adenoviruses do not have helical capsids. C is incorrect as there is no situation where adenoviruses have helical capsids. D is incorrect as there is a clear correct answer, which is B.

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.

Correct Answer: C

Rationale: The correct answer is C: Kirby-Bauer disk diffusion test. This test is used to determine the antibiotic susceptibility of bacteria by measuring the zone of inhibition around antibiotic-soaked paper disks. It helps identify which antibiotics are effective against the bacteria being tested. This test is crucial in guiding antibiotic treatment decisions. A: Gram stain is used to classify bacteria based on their cell wall composition and morphology, not for antibiotic susceptibility testing. B: Catalase test is used to differentiate between catalase-positive and catalase-negative bacteria, not for antibiotic susceptibility testing. D: Endospore stain is used to detect the presence of endospores in bacteria, not for antibiotic susceptibility testing.

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.

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas aeruginosa. Pseudomonas aeruginosa is known for producing a blue-green pigment called pyocyanin, which gives the characteristic color seen in the wound abscess. The distinctive odor of jasmine is also a key feature of Pseudomonas aeruginosa. Proteus vulgaris (B) and Klebsiella pneumoniae (D) do not produce blue-green pigment or have a jasmine-like odor. Escherichia coli (C) typically does not produce blue-green pigment or have a jasmine-like odor.

Correct Answer: A

Rationale: The correct answer is A: Isoniazid and rifampicin. These drugs are considered first-line treatment for tuberculosis due to their high efficacy and low toxicity. Isoniazid targets the cell wall of the tuberculosis bacteria, while rifampicin inhibits RNA synthesis. They are recommended by WHO as the first choice for treating tuberculosis. Choice B (Penicillin and erythromycin) is incorrect because these antibiotics are not effective against tuberculosis bacteria. Choice C (Trimethoprim and third generation cephalosporins) is incorrect because they are not considered first-line drugs for tuberculosis treatment. Choice D (All the listed above can be used depending on their resistance profile) is incorrect because only isoniazid and rifampicin are universally recognized as first-line drugs for tuberculosis regardless of resistance profile.

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.