microbiology an introduction 13th edition test bank

Correct Answer: A

Rationale: Step 1: Understand haematogenic spread means bacteria traveling through blood. Step 2: Urinary tract infections typically occur due to bacteria entering through urethra, not via blood. Step 3: Choice A states bacterial UTIs are usually after haematogenic spread, which is incorrect. Step 4: Therefore, Choice A is NOT true for UTIs. Summary: B, C, and D are incorrect as they align with typical characteristics of UTIs.

Correct Answer: C

Rationale: The bacterial capsule is composed of polysaccharides. This outer layer helps bacteria evade the host immune system, protect against desiccation, and aid in attachment to host cells. Polysaccharides are long chains of sugar molecules, providing a protective barrier for the bacteria. Lipopolysaccharides (choice A) are found in the outer membrane of Gram-negative bacteria and are not a major component of the capsule. Teichoic acid (choice B) is a component of the cell wall in Gram-positive bacteria, not the capsule. Peptidoglycan (choice D) is another component of the cell wall but is not part of the capsule.

Correct Answer: A

Rationale: The most likely diagnosis is Actinomycosis. This is because the patient's presentation of a painful swelling with a fistula containing white granules and yellow-green honeycomb-like tissue is classic for Actinomycosis. Actinomyces is a gram-positive anaerobic bacterium that forms sulfur granules in tissues. Tuberculosis (B) typically presents with caseating granulomas, not sulfur granules. Leprosy (C) presents with skin lesions and nerve damage, not characteristic of this case. Syphilis (D) usually presents with painless ulcers and rash, not the painful swelling and fistula seen in this patient.

Correct Answer: A

Rationale: The correct answer is A: Benzylpenicillin sodium salt. Benzylpenicillin is a beta-lactam antibiotic that inhibits the synthesis of bacterial cell walls by disrupting the formation of murein (peptidoglycan), leading to bacterial cell death. This mechanism specifically targets the causative agent of syphilis, Treponema pallidum. - Choice B: Bijochinol is not a known drug used to treat syphilis. - Choice C: Ciprofloxacin is a fluoroquinolone antibiotic that works by inhibiting bacterial DNA replication and is not the first-line treatment for syphilis. - Choice D: Azithromycin is a macrolide antibiotic that interferes with bacterial protein synthesis and is commonly used to treat other infections but is not the preferred treatment for syphilis.

Correct Answer: A

Rationale: The correct answer is A: Bacillus anthracis. The presence of Gram-positive rods with central spores, catalase-positive, and aerobic growth characteristics are indicative of Bacillus anthracis. Bacillus anthracis is known for its central spores and ability to grow aerobically. Summary of why other choices are incorrect: B: Clostridium tetani is a Gram-positive rod with terminal spores and is anaerobic. C: Streptococcus pyogenes is a Gram-positive cocci and catalase-negative. D: Klebsiella pneumoniae is a Gram-negative rod and catalase-positive, but is not associated with central spores.