microbiology test bank

Correct Answer: B

Rationale: The correct answer is B: Phylum. After class in the classification system comes phylum. The classification system starts with the broadest category, which is the kingdom, followed by phylum, class, order, family, genus, and species. Phylum is a higher level of classification than class, so it comes next in the hierarchy. Domain is a higher level than kingdom, and order is a lower level of classification than class. Therefore, the correct sequence is kingdom, phylum, class, order.

Correct Answer: D

Rationale: The correct answer is D (All of the above) as all three bacteria (Escherichia coli, Salmonella enterica, Neisseria meningitidis) produce endotoxins causing fever and shock. Endotoxins are lipopolysaccharides found in the outer membrane of Gram-negative bacteria and can trigger an immune response leading to fever and shock. Escherichia coli and Salmonella enterica are common causes of food poisoning and sepsis, while Neisseria meningitidis is responsible for meningococcal meningitis and septicemia. Therefore, all three choices are correct in producing endotoxins that can cause fever and shock.

Correct Answer: A

Rationale: The correct answer is A because penicillins and cephalosporins inactivate transpeptidase activity of penicillin binding proteins, leading to disruption of bacterial cell wall synthesis. This mechanism makes them bactericidal, not bacteriostatic (choice B). Choice C is incorrect as penicillins and cephalosporins target cell wall synthesis, not the cytoplasmic membrane. Choice D is incorrect as option A is the correct statement.

Correct Answer: A

Rationale: Step 1: Chlorhexidine belongs to the group of biguanides, making choice A accurate. Step 2: It is commonly used for disinfection of hands, skin, and mucous membranes. Step 3: It has a broad spectrum of antimicrobial activity, making it widely applicable. Summary: Choice B is incorrect as chlorhexidine is not classified as an alcohol. Choice C is incorrect as chlorhexidine has various applications. Choice D is incorrect as chlorhexidine is generally safe for use with low toxicity.

Correct Answer: A

Rationale: The correct answer is A: Bacteria. Urinary tract infections (UTIs) are primarily caused by the invasion of bacteria into the urinary tract. Bacteria, especially Escherichia coli (E. coli), are the most common culprits. They enter the urinary tract through the urethra and can multiply in the bladder, leading to infection. Viruses (choice B) and fungi (choice C) are not typical causes of UTIs. "None of the above" (choice D) is incorrect as bacteria are indeed the main cause of UTIs.