ATI RN
microbiology an introduction test bank Questions
Question 1 of 9
The cell surface of pathogenic gram-negative bacteria can be covered in villi and cilia. What function do these structures have?
Correct Answer: C
Rationale: The correct answer is C: Bacterial adhesion to the surface of the host cells, conjugation. Villi and cilia on the cell surface of pathogenic bacteria help in bacterial adhesion to host cells, facilitating the process of infection. Conjugation is the transfer of genetic material between bacterial cells, which can be aided by these structures. The other choices are incorrect because RNA exchange between cells (A) is typically facilitated by different structures like pili, inhibition of complement activity (B) is not related to the function of villi and cilia, and resistance to antibody opsonization (D) is usually achieved through other mechanisms such as capsule formation.
Question 2 of 9
A Gram-stained smear from a wound revealed Gram-positive rods with terminal spores. The bacteria were anaerobic and produced gas. What is the most likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Clostridium perfringens. This bacterium is an anaerobic, Gram-positive rod that forms terminal spores and produces gas. It is commonly associated with wound infections and gas gangrene. Clostridium botulinum causes botulism and does not typically present with gas production. Bacillus anthracis is an aerobic, Gram-positive spore-forming bacterium causing anthrax. Clostridium tetani causes tetanus and does not produce gas. Thus, based on the characteristics described in the question, Clostridium perfringens is the most likely causative agent.
Question 3 of 9
A child presented with foul-smelling diarrhea. Stool microscopy revealed trophozoites with two nuclei and flagella. What is the causative agent?
Correct Answer: A
Rationale: The correct answer is A: Giardia lamblia. Giardia lamblia is a protozoan parasite that causes foul-smelling diarrhea. The trophozoites of Giardia lamblia have two nuclei and flagella, which are characteristic features seen on stool microscopy. The presence of these specific features helps differentiate Giardia lamblia from the other options. Entamoeba histolytica (B) typically presents with one nucleus and lacks flagella. Trichomonas vaginalis (C) is a sexually transmitted parasite with a different morphology. Balantidium coli (D) is a ciliated parasite, not flagellated like Giardia lamblia.
Question 4 of 9
While registering the child to the school Mantoux's test was made to define whether revaccination was needed test result is negative. What does this result of the test mean?
Correct Answer: D
Rationale: Step 1: Mantoux test measures cell-mediated immunity response to tuberculosis. Step 2: A negative result means no significant immune response to TB antigens. Step 3: Option A is incorrect, as it refers to antitoxic immunity, not cell immunity. Step 4: Option B is incorrect, as it mentions antibodies, not cell-mediated immunity. Step 5: Option C is incorrect, as it states absence of antibodies, not cell immunity. Step 6: Option D is correct as it directly correlates with the purpose of Mantoux test.
Question 5 of 9
Gram staining is used to differentiate bacteria based on:
Correct Answer: C
Rationale: The correct answer is C: cell wall composition. Gram staining differentiates bacteria based on the structure of their cell walls. It classifies bacteria into Gram-positive (thick peptidoglycan layer) and Gram-negative (thin peptidoglycan layer). This differentiation is crucial for identifying bacterial species and guiding treatment choices. Size and shape (choice A) are not specific to Gram staining. Presence of flagella (choice B) is related to bacterial motility, not Gram staining. Genetic material (choice D) is not directly assessed by Gram staining. Overall, the unique composition of the cell wall is the key factor in distinguishing bacteria through Gram staining.
Question 6 of 9
A 45-year-old patient complains of body temperature rise up to 40oC, general weakness, headache, painfulness and spastic muscle contractions around the wound in the shin. He received this wound 5 days ago when working in his garden. He requested no medical care back then. What wound infection can be suspected?
Correct Answer: A
Rationale: The correct answer is A: Tetanus. The patient's symptoms of muscle contractions, fever, and wound history suggest tetanus, caused by Clostridium tetani bacteria commonly found in soil. The spastic muscle contractions around the wound are classic for tetanus due to the neurotoxin produced by the bacteria. General weakness and headache are also common symptoms. B: Anthrax is unlikely as it presents with different symptoms such as skin lesions, respiratory symptoms, and gastrointestinal symptoms. C: Erysipelas is characterized by red, swollen patches on the skin, not consistent with the symptoms described. D: Gram-positive is not a specific diagnosis but a broad category of bacteria. Tetanus is caused by Clostridium tetani, which is a Gram-positive bacterium, but this choice does not provide a specific infection diagnosis.
Question 7 of 9
Microscopic examination of pus sample taken from mandibular fistula canal and stained by Gram's method has revealed druses with gram-positive coloring in the center and cone-shaped structures with gram-negative coloring. Such morphology is characteristic of the agent of:
Correct Answer: B
Rationale: The correct answer is B: Actinomycosis. Actinomyces is a gram-positive bacterium that forms sulfur granules (druses) with gram-positive coloring in the center and filamentous structures resembling cones with gram-negative coloring. This morphology is characteristic of Actinomyces species. Fusobacteriosis (choice A) typically presents with gram-negative rods. Staphylococcal osteomyelitis (choice C) is caused by gram-positive staphylococci, not Actinomyces. Anaerobic infections (choice D) can be caused by various bacteria, but the specific morphology described in the question matches Actinomyces, making choice B the correct answer.
Question 8 of 9
The cell surface of pathogenic gram-negative bacteria can be covered in villi and cilia. What function do these structures have?
Correct Answer: C
Rationale: The correct answer is C: Bacterial adhesion to the surface of the host cells, conjugation. Villi and cilia on the cell surface of pathogenic bacteria help in bacterial adhesion to host cells, facilitating the process of infection. Conjugation is the transfer of genetic material between bacterial cells, which can be aided by these structures. The other choices are incorrect because RNA exchange between cells (A) is typically facilitated by different structures like pili, inhibition of complement activity (B) is not related to the function of villi and cilia, and resistance to antibody opsonization (D) is usually achieved through other mechanisms such as capsule formation.
Question 9 of 9
The key diagnostic feature of Corynebacterium diphtheriae is:
Correct Answer: B
Rationale: The correct answer is B: presence of metachromatic granules. This is because Corynebacterium diphtheriae is known for containing metachromatic granules, which are characteristic of this species. These granules can be observed under a microscope and aid in the identification of the bacteria. Explanation of other choices: A: formation of spores - Corynebacterium diphtheriae does not form spores. Spore formation is more commonly seen in bacteria such as Bacillus and Clostridium species. C: production of coagulase - Coagulase production is a characteristic of Staphylococcus aureus, not Corynebacterium diphtheriae. D: beta-hemolysis on blood agar - Corynebacterium diphtheriae does not exhibit beta-hemolysis on blood agar. This type of hemolysis is more typical of Streptococcus pyogenes.