ATI RN
microbiology basic and clinical principles test bank Questions
Question 1 of 5
A blood culture from a patient with sepsis revealed Gram-negative diplococci. The bacteria were oxidase-positive and fermentative. What is the most likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Neisseria meningitidis. Step 1: Gram-negative diplococci - characteristic of Neisseria species. Step 2: Oxidase-positive - Neisseria species are oxidase-positive. Step 3: Fermentative - Neisseria meningitidis is a fermentative bacterium. Therefore, Neisseria meningitidis is the most likely causative agent. Summary: - B: Neisseria gonorrhoeae is also a Neisseria species but is not fermentative. - C: Moraxella catarrhalis is oxidase-positive but not fermentative. - D: Haemophilus influenzae is not a Neisseria species and is not typically fermentative.
Question 2 of 5
A lymph node punctate of a patient with suspected protozoa disease was examined. Examination of the stained specimen (Romanovsky's stain) revealed some crescent bodies with pointed end, blue cytoplasm and red nucleus. What protozoan were revealed in the smears?
Correct Answer: B
Rationale: The correct answer is B: Malarial plasmodiums. The description of crescent bodies with a pointed end, blue cytoplasm, and red nucleus corresponds to the characteristics of Plasmodium species seen in Romanovsky's stain. Plasmodium species are known to cause malaria and have distinct features like the ones described. Incorrect choices: A: Toxoplasmas - Toxoplasma gondii typically appear as tachyzoites or bradyzoites under staining, not crescent bodies. C: Dermotropic leishmania - Leishmania species appear as amastigotes in tissue smears, not crescent bodies. D: Viscerotropic leishmania - Similar to choice C, Leishmania species do not typically present as crescent bodies in stained specimens.
Question 3 of 5
A 12-year-old boy presents with nausea, frequent repeated vomiting that first occurred after eating canned vegetables. Objectively: the patient has dry mucous membranes, muscular hypotonia, anisocoria, mydriasis, dysphagia and dysarthria. What is the most likely diagnosis?
Correct Answer: A
Rationale: The most likely diagnosis is A: Botulism. The symptoms, such as nausea, vomiting after eating canned vegetables, dry mucous membranes, muscular hypotonia, anisocoria, mydriasis, dysphagia, and dysarthria, are classic signs of botulism poisoning. Botulism is caused by the neurotoxin produced by Clostridium botulinum bacteria found in improperly canned or preserved food. The neurotoxin affects the nervous system, leading to symptoms like those described. Shigellosis (B), Salmonellosis (C), and Cholera (D) typically present with different symptoms such as diarrhea, fever, and abdominal pain, which are not seen in this patient.
Question 4 of 5
It is often difficult for antibiotics to effectively reach the infection site of osteomyelitis primarily because of:
Correct Answer: A
Rationale: The correct answer is A: destruction of the local blood supply. In osteomyelitis, the infection occurs in the bone, which has a relatively poor blood supply compared to soft tissues. This limited blood flow makes it challenging for antibiotics to reach the infection site effectively, hindering their ability to combat the infection. Destruction of the local blood supply restricts the delivery of antibiotics and immune cells to the infected bone, leading to poor treatment outcomes. Summary: - Option A is correct because the limited blood supply in bones hinders antibiotic delivery. - Option B is incorrect as denaturing by normal flora does not impact antibiotic reach to the infection site. - Option C is incorrect as inflammation and edema, while present, do not primarily hinder antibiotic delivery. - Option D is incorrect as excessive pus production does not directly impede antibiotic access to the infection site.
Question 5 of 5
The most commonly acquired laboratory infections are caused by
Correct Answer: A
Rationale: The correct answer is A: bacteria. Bacteria are the most common cause of laboratory-acquired infections due to their ability to survive and multiply in various environments. They can easily contaminate lab equipment and surfaces, leading to infections if proper precautions are not taken. Viruses (choice B) are less common in laboratory-acquired infections as they require specific conditions to survive outside a host. Protozoans (choice C) are larger and less likely to be transmitted in a laboratory setting. Prions (choice D) are misfolded proteins and are not considered living organisms, making them an unlikely source of laboratory infections.
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