ATI RN
microbiology chapter 12 test bank Questions
Question 1 of 9
Which toxin is specific for ETEC:
Correct Answer: D
Rationale: The correct answer is D: LT enterotoxin. This toxin is specific for Enterotoxigenic E. coli (ETEC) and is responsible for causing diarrhea by increasing cyclic AMP levels in intestinal cells. TSST-1 (choice A) is produced by Staphylococcus aureus, not ETEC. Shiga-like toxin (choice B) is produced by Shigella and EHEC, not ETEC. Erythrogenic toxin (choice C) is produced by Streptococcus pyogenes, not ETEC. Therefore, the LT enterotoxin is the specific toxin associated with ETEC.
Question 2 of 9
A patient with fever, chills, and neck stiffness had a cerebrospinal fluid sample with Gram-negative diplococci. What is the likely diagnosis?
Correct Answer: A
Rationale: The likely diagnosis is Meningococcal meningitis (Choice A) due to the presence of Gram-negative diplococci in the cerebrospinal fluid. Neisseria meningitidis is a Gram-negative diplococcus commonly associated with meningococcal meningitis. Fever, chills, and neck stiffness are classic symptoms of bacterial meningitis, and Neisseria meningitidis often presents with these symptoms. Pneumococcal meningitis (Choice B) is caused by Streptococcus pneumoniae, a Gram-positive organism. Haemophilus influenzae (Choice C) is also a Gram-negative organism but typically presents with a different clinical picture. Listeria monocytogenes (Choice D) is a Gram-positive rod and is more commonly associated with meningitis in neonates, elderly, and immunocompromised individuals.
Question 3 of 9
Which bacteria are capable of producing an exotoxin that causes severe diarrhea?
Correct Answer: D
Rationale: The correct answer is D because all three bacteria listed are capable of producing exotoxins that can cause severe diarrhea. Escherichia coli can produce toxins that lead to diarrhea. Clostridium botulinum produces a neurotoxin causing botulism, which can also result in diarrhea. Vibrio cholerae is known for producing cholera toxin, a potent exotoxin that causes severe watery diarrhea. The other choices are incorrect because each bacterium listed is capable of producing a toxin that can cause diarrhea.
Question 4 of 9
The presence of flagella in bacterial cell represents:
Correct Answer: A
Rationale: The presence of flagella in a bacterial cell represents the H-antigen. Flagella are protein structures on the cell surface that play a role in bacterial motility. The H-antigen refers to the flagellar antigen, which is involved in immune responses and bacterial identification. Option A is correct because flagella are specifically associated with the H-antigen. Summarily, choices B and C are incorrect because the O-antigen and K-antigen are associated with lipopolysaccharide and capsule antigens, respectively, not flagella. Option D is incorrect as well because the correct association is with the H-antigen.
Question 5 of 9
Gram (+) bacteria ... MG-ribonucleate and Mg. deoxyribonucleate in:
Correct Answer: A
Rationale: The correct answer is A, proportion 4:1. Gram (+) bacteria have a higher ratio of MG-ribonucleate to Mg. deoxyribonucleate because ribosomal RNA is more abundant in actively growing bacterial cells. This higher proportion of MG-ribonucleate to Mg. deoxyribonucleate is essential for protein synthesis and growth. The other choices are incorrect because they do not reflect the higher ratio of ribosomal RNA to DNA in Gram (+) bacteria, which is crucial for their metabolic activities and cellular functions.
Question 6 of 9
The basic requirements of PCR reaction include:
Correct Answer: D
Rationale: The correct answer is D because all the options are essential for a PCR reaction. A: DNA segment is required as the template for amplification. B: Two oligonucleotide primers are needed to initiate DNA replication. C: Heat stable DNA polymerase (not just heat stable DNA) is crucial for withstanding the high temperatures during PCR. In summary, without any of these components, the PCR reaction cannot proceed effectively.
Question 7 of 9
Which toxin is specific for ETEC:
Correct Answer: D
Rationale: The correct answer is D: LT enterotoxin. This toxin is specific for Enterotoxigenic E. coli (ETEC) and is responsible for causing diarrhea by increasing cyclic AMP levels in intestinal cells. TSST-1 (choice A) is produced by Staphylococcus aureus, not ETEC. Shiga-like toxin (choice B) is produced by Shigella and EHEC, not ETEC. Erythrogenic toxin (choice C) is produced by Streptococcus pyogenes, not ETEC. Therefore, the LT enterotoxin is the specific toxin associated with ETEC.
Question 8 of 9
When cultured on solid growth media, bacteria with long O-specific chains form:
Correct Answer: A
Rationale: The correct answer is A: Smooth S colonies. Bacteria with long O-specific chains are known as smooth strains, and when cultured on solid growth media, they form smooth colonies due to the presence of the O antigen. This gives them a glossy appearance. Rough R colonies (Choice B) lack O antigen and appear rough. Mucoid -M colonies (Choice C) are associated with capsules, not O-specific chains. H colonies (Choice D) are not relevant to the O-specific chains. Smooth S colonies are the characteristic phenotype of bacteria with long O-specific chains when cultured on solid media.
Question 9 of 9
The term bacilli is related to:
Correct Answer: B
Rationale: The term bacilli refers to rod-shaped bacteria, typically found in the Gram-positive group. Spore-forming bacteria, such as Bacillus and Clostridium, are characterized by their rod shape. Choice A is incorrect as the color in Gram staining does not define bacilli. Choice C is incorrect as peptidoglycan content does not determine the classification of bacilli. Choice D is incorrect as bacilli do have a specific characteristic. Therefore, the correct answer is B due to the shape and characteristic of spore-forming bacteria.