ATI RN
medical microbiology test bank Questions
Question 1 of 9
Which of the following statements regarding the antigenic shift is NOT true?
Correct Answer: D
Rationale: The correct answer is D because antigenic shift is a major change in the influenza virus where genetic material from different influenza viruses mix to create a new subtype. This is a large-scale change that results in a novel virus with a different antigenic composition. Option A and B are incorrect because antigenic shift does involve the exchange of genetic information between animal and human influenza A viruses, and it does occur when animal or avian influenza viruses of type A directly pass into the human population. Option C is incorrect because antigenic shift is not related to the recirculation of a previously circulating influenza strain.
Question 2 of 9
The bacterial endospore is primarily composed of:
Correct Answer: B
Rationale: The correct answer is B: peptidoglycan and calcium dipicolinate. Bacterial endospores are resistant structures formed by certain bacterial species under unfavorable conditions. Peptidoglycan provides structural support, while calcium dipicolinate aids in heat resistance. Lipid bilayers (choice A) are not a primary component. Capsular polysaccharides (choice C) are part of the bacterial capsule, not the endospore. Teichoic acid (choice D) is a component of the cell wall, not the endospore.
Question 3 of 9
Before a surgery the patient was prescribed a synthetic antiprotozoal drug for prevention of wound infection. The prescribed drug is highly effective against Helicobacter pylori. Name this drug:
Correct Answer: A
Rationale: Step-by-step rationale: 1. Metronidazole is a synthetic antiprotozoal drug commonly used for wound infection prevention. 2. It is highly effective against Helicobacter pylori, a bacterium that causes stomach ulcers. 3. Metronidazole works by disrupting DNA structure in bacteria, leading to their death. 4. Chingamin (Chloroquine) is an antimalarial drug, not effective against Helicobacter pylori. 5. Doxycycline hydrochloride is an antibiotic used for bacterial infections, not specifically for H. pylori. 6. Aciclovir is an antiviral drug used for herpes infections, not effective against H. pylori. Summary: Metronidazole is the correct answer as it is specifically effective against H. pylori and commonly used for wound infection prevention. Other choices are incorrect as they target different types of infections.
Question 4 of 9
A 43 y.o. patient was admitted to the hospital with complaints of high temperature of the body and severe headache. On examination: carbuncle is revealed on the forearm. There are intense edema around it, insignificant pain, regional lymphadenitis. The patient is a worker of cattle-ranch. What disease is it necessary to think about first?
Correct Answer: D
Rationale: The correct answer is D: Erysipeloid. Erysipeloid is a bacterial infection caused by Erysipelothrix rhusiopathiae commonly found in animals like cattle. The patient's occupation as a cattle-ranch worker puts them at risk for this infection. Symptoms such as high body temperature, severe headache, carbuncle on the forearm with edema, and regional lymphadenitis are typical of erysipeloid. Anthrax (A) is more associated with skin lesions and severe systemic symptoms. Carcinoma of skin (B) presents differently with slow-growing skin lesions. Erysipelas (C) is a different bacterial infection characterized by red, swollen patches on the skin.
Question 5 of 9
A consumptive patient has an open pulmonary form of disease. Choose what sputum staining should be selected for finding out the tubercle (Koch's) bacillus?
Correct Answer: A
Rationale: The correct answer is A. Method of Ziel-Neelsen. This method uses a special stain (carbol fuchsin) to detect acid-fast organisms like Mycobacterium tuberculosis, the causative agent of tuberculosis. The staining procedure involves heating the slide to help penetrate the mycolic acid layer of the bacteria, making them resistant to decolorization by acid-alcohol. The red stained acid-fast bacilli stand out against the blue counterstain. This method is specific for identifying tubercle bacilli in sputum samples. Choice B: Method of Romanowsky-Giemsa is used for staining blood smears and is not suitable for detecting acid-fast bacilli in sputum. Choice C: Method of Gram is used for staining bacteria based on their cell wall composition and is not effective for identifying acid-fast bacilli like Mycobacterium tuberculosis. Choice D: Method of Neisser is not a specific staining method for acid-fast bacilli and is not suitable
Question 6 of 9
Sexually transmitted infection, Lymphogranuloma venerum, is caused by:
Correct Answer: D
Rationale: The correct answer is D: Chlamydia trachomatis. Lymphogranuloma venereum (LGV) is caused by Chlamydia trachomatis serovars L1, L2, and L3. These serovars infect the lymphatic system leading to swelling and inflammation. Choice A, Chlamydia pneumoniae, is associated with respiratory infections, not LGV. Choice B, Chlamydia psittaci, causes psittacosis in birds and humans. Choice C, Mycoplasma genitalium, is a separate STI but is not the causative agent for LGV. The key to the correct answer is understanding the specific pathogen responsible for LGV based on its clinical presentation and mode of transmission.
Question 7 of 9
2 weeks since the blood transfusion a recepient has developed fever. What protozoal disease can it be?
Correct Answer: B
Rationale: The correct answer is B: Malaria. Fever developing 2 weeks post-blood transfusion is characteristic of malaria due to the incubation period of the parasite. Trypanosomiasis presents earlier, amebiasis usually causes GI symptoms, and toxoplasmosis typically manifests with flu-like symptoms. Malaria is the most likely cause based on the timing and clinical presentation.
Question 8 of 9
On examination of a 6-year-old child the doctor noticed greyish film on the child's tonsils. Microscopy of the smear stained by Neisser method detected there Corynebacterium diphtheria. What morphologic feature was the most indicative for determining the type of the agent?
Correct Answer: C
Rationale: The correct answer is C: Polar placement of volutin granules. This feature is indicative of Corynebacterium diphtheria. Volutin granules are metachromatic granules found in the polar region of the bacterial cell, which is characteristic of this species. This feature helps differentiate it from other bacteria. Explanation: A: Fence-like position of the agent's cells is not a specific morphologic feature of Corynebacterium diphtheria. B: Spores that exceed cells in diameter is not a characteristic feature of Corynebacterium diphtheria. D: Presence of the capsule is not a distinguishing morphologic feature of Corynebacterium diphtheria. In summary, the polar placement of volutin granules is the most indicative feature for determining the type of agent as Corynebacterium diphtheria, making it the correct choice.
Question 9 of 9
The lipopolysaccharides of gram negative bacteria consists of all the following types except:
Correct Answer: D
Rationale: The correct answer is D: Protoplast. Lipopolysaccharides of Gram-negative bacteria consist of three main components: O-specific polysaccharide chain, R-specific polysaccharide chain, and Lipid A. Protoplast is not a component of lipopolysaccharides. O-specific polysaccharide chain is responsible for serotype specificity, R-specific polysaccharide chain varies among strains, and Lipid A is the endotoxin component. Protoplast refers to a bacterial cell devoid of a cell wall, which is not a component of lipopolysaccharides.