A patient with a wound infection had a Gram-positive cocci isolated from the sample. The bacteria were catalase-positive and coagulase-positive. What is the likely causative agent?

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microbiology chapter 10 test bank Questions

Question 1 of 9

A patient with a wound infection had a Gram-positive cocci isolated from the sample. The bacteria were catalase-positive and coagulase-positive. What is the likely causative agent?

Correct Answer: A

Rationale: The correct answer is A: Staphylococcus aureus. This is because Staphylococcus aureus is Gram-positive, catalase-positive, and coagulase-positive, which matches the characteristics described in the question. Staphylococcus epidermidis is also Gram-positive but is coagulase-negative. Streptococcus pneumoniae is Gram-positive but is catalase-negative. Enterococcus faecalis is Gram-positive but is catalase-negative and coagulase-negative. Therefore, based on the given information, Staphylococcus aureus is the likely causative agent of the wound infection.

Question 2 of 9

What drug should be administered?

Correct Answer: A

Rationale: The correct answer is A: Doxycycline. It is a broad-spectrum antibiotic effective against a wide range of bacteria, including those causing infections like Lyme disease and pneumonia. Doxycycline is often the first-line treatment for these infections due to its efficacy and low risk of resistance. Chloramphenicol (B) has serious side effects and is reserved for specific cases. Penicillin (C) is not effective against all bacteria and may not cover the specific infection. Streptomycin (D) is mainly used for certain types of bacterial infections and is not the optimal choice for the conditions mentioned in the question.

Question 3 of 9

A smear from frothy and purulent vaginal discharges of a 42 y.o. woman was stained by Romanovsky-Giemsa method. Its analysis revealed some microorganisms of flagellates class. What microorganism were the most probably revealed?

Correct Answer: A

Rationale: The correct answer is A: Trichomonas vaginalis. Trichomonas vaginalis is a flagellated protozoan that causes trichomoniasis, a sexually transmitted infection commonly found in vaginal discharges. In this case, the presence of flagellates in the vaginal discharge aligns with the characteristics of Trichomonas vaginalis. Leishmania donovani causes leishmaniasis, transmitted by sandflies. Trypanosoma gambiense causes African sleeping sickness through the tsetse fly bite. Trihomonas hominis is a non-pathogenic flagellate found in the human intestine. Therefore, the correct choice is A due to the correlation between the flagellates found in the vaginal discharge and the characteristics of Trichomonas vaginalis.

Question 4 of 9

A patient with diarrhea had a stool sample that revealed Gram-negative rods that fermented lactose. What is the most likely causative agent?

Correct Answer: A

Rationale: The correct answer is A: Escherichia coli. Step-by-step rationale: 1. Gram-negative rods: E. coli is a Gram-negative rod bacterium. 2. Fermented lactose: E. coli is known to ferment lactose. 3. Common cause of diarrhea: E. coli is a common causative agent of infectious diarrhea. Summary: B: Salmonella typhi causes typhoid fever, not typically associated with lactose fermentation. C: Shigella dysenteriae causes dysentery, not known for lactose fermentation. D: Proteus vulgaris is not a common cause of infectious diarrhea and does not typically ferment lactose.

Question 5 of 9

A patient with a painful ulcer had a wound culture revealing Gram-negative rods with a characteristic 'safety pin' appearance. What is the most likely causative agent?

Correct Answer: A

Rationale: The correct answer is A: Yersinia pestis. Y. pestis is a Gram-negative rod that exhibits a 'safety pin' appearance on staining due to bipolar staining. This bacterium is the causative agent of plague, which can present as painful ulcers known as buboes. Y. pestis is transmitted by fleas and can cause outbreaks in humans. Summary: - B: Francisella tularensis causes tularemia, not typically associated with painful ulcers. - C: Brucella abortus causes brucellosis, which does not typically present with painful ulcers. - D: Clostridium botulinum causes botulism, characterized by muscle weakness and paralysis, not painful ulcers.

Question 6 of 9

Microbial life on teeth was first observed by:

Correct Answer: C

Rationale: The correct answer is C: Van Leeuwenhoek. Van Leeuwenhoek was a Dutch scientist known for his pioneering work in microscopy. He was the first to observe microbial life, including bacteria on teeth, using his handmade microscopes in the 17th century. Jenner (choice A) is known for developing the smallpox vaccine, not for microbial observations. Semmelweis (choice B) discovered the importance of handwashing in preventing infections. Pasteur (choice D) is famous for his work on pasteurization and germ theory, but not specifically for observing microbial life on teeth. Van Leeuwenhoek's meticulous observations and groundbreaking discoveries make him the correct choice in this context.

Question 7 of 9

Which of the following pathogens can be transmitted through the placenta?

Correct Answer: A

Rationale: The correct answer is A: Listeria monocytogenes. This pathogen can cross the placenta and infect the fetus, leading to serious complications. Listeria can cause miscarriage, stillbirth, or severe neonatal infections. Staphylococcus aureus and Corynebacterium diphtheriae do not typically cross the placenta. Choice D is incorrect because Listeria monocytogenes can indeed be transmitted through the placenta, unlike the other pathogens listed.

Question 8 of 9

Examination of a child revealed some whitish spots looking like coagulated milk on the mucous membrane of his cheeks and tongue. Analysis of smears revealed gram-positive oval yeast-like cells. What causative agents are they?

Correct Answer: A

Rationale: The correct answer is A: Candida. The whitish spots resembling coagulated milk on the mucous membranes are characteristic of oral thrush, a condition caused by Candida species. Candida is a gram-positive oval yeast-like fungus commonly found in the oral cavity. Staphylococci (B) are gram-positive cocci, not yeast-like cells. Diphtheria bacillus (C) causes diphtheria, not oral thrush. Actinomycetes (D) are filamentous bacteria, not yeast-like cells typically seen in oral thrush. Therefore, A is the correct answer based on the clinical presentation and microscopic findings.

Question 9 of 9

A bloodborne training program for certain professions was established by and is required by

Correct Answer: A

Rationale: The correct answer is A: OSHA. The Occupational Safety and Health Administration (OSHA) is responsible for setting and enforcing safety standards in the workplace, including bloodborne pathogen training requirements. OSHA's Bloodborne Pathogens Standard mandates training for certain at-risk professions to prevent exposure to bloodborne diseases. The CDC (Choice B) focuses on disease prevention and control, not regulatory enforcement. NIA (Choice C) is the National Institute on Aging and not relevant to bloodborne training. WHO (Choice D) is the World Health Organization, which sets global health standards but does not regulate workplace safety in the same capacity as OSHA.

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