microbiology chapter 11 test bank

Correct Answer: B

Rationale: The correct answer is B: Rickettsia rickettsii. Rocky Mountain spotted fever is caused by Rickettsia rickettsii, a bacterium transmitted by ticks. This pathogen primarily affects the endothelial cells of blood vessels, leading to vasculitis. Borrelia burgdorferi (choice A) causes Lyme disease, not Rocky Mountain spotted fever. Rickettsia prowazekii (choice C) causes epidemic typhus, and Ehrlichia chaffeensis (choice D) causes human monocytic ehrlichiosis, both of which are distinct from Rocky Mountain spotted fever. Therefore, the correct choice is B based on the specific etiology of the disease.

Correct Answer: A

Rationale: The most likely diagnosis is Reiter's syndrome. This is suggested by the presence of joint pain, fever, elevated ESR and CRP levels, and chlamydia infection. Reiter's syndrome is a reactive arthritis triggered by an infection elsewhere in the body, such as chlamydia. The patient's symptoms of joint pain and swelling, along with the positive chlamydia test, support this diagnosis. Rheumatic arthritis (Choice B) is not associated with chlamydia infection, making it less likely. Gout (Choice C) typically presents with elevated uric acid levels, which are normal in this case. Bechterew's disease (Choice D) primarily affects the spine and sacroiliac joints, not the sternoclavicular and knee joints as seen in this patient.

Correct Answer: A

Rationale: The correct answer is A: Staphylococcus aureus. This bacterium is characterized by Gram-positive cocci in clusters, catalase-positive, and coagulase-positive. Staphylococcus aureus is a common pathogen causing wound infections due to its ability to produce toxins and enzymes. Staphylococcus epidermidis (B) is catalase-positive but coagulase-negative, making it less likely to cause infections. Streptococcus pyogenes (C) is catalase-negative and typically causes streptococcal infections, not wound infections. Enterococcus faecalis (D) is catalase-negative and typically associated with urinary tract infections. Thus, Staphylococcus aureus is the most likely causative agent based on the given characteristics.

Correct Answer: B

Rationale: The correct answer is B: Streptolysin. Streptolysin is a toxin released by Streptococcus pyogenes that causes lysis of red blood cells and contributes to the pathogenicity of the bacteria. Enterotoxin (Choice A) is typically produced by Staphylococcus aureus, not Streptococcus pyogenes. Staphylocoagulase (Choice C) is an enzyme produced by Staphylococcus aureus to promote blood clot formation and is not associated with Streptococcus pyogenes. Therefore, the correct answer is B as Streptolysin is the toxin released by Streptococcus pyogenes.

Correct Answer: A

Rationale: The correct answer is A: Tuberculin. The Mantoux test involves injecting tuberculin, a protein derivative of Mycobacterium tuberculosis, under the skin to check for a delayed hypersensitivity reaction in individuals exposed to TB. B: BCG vaccine is a live attenuated vaccine used for TB prevention, not for diagnostic testing. C: DTP vaccine is for diphtheria, tetanus, and pertussis, not TB. D: Tularinum is not a standard immunobiological preparation used for TB testing. Therefore, A is the correct choice for the Mantoux test.