ATI RN
microbiology chapter 1 test bank Questions
Question 1 of 5
A patient with dysentery had a stool sample that was cultured on Endo agar, resulting in colorless colonies. The bacteria were Gram-negative rods. What is the most likely causative agent?
Correct Answer: A
Rationale: Rationale: 1. Endo agar inhibits the growth of Gram-positive bacteria. 2. Colorless colonies on Endo agar indicate lactose non-fermenting bacteria. 3. Shigella dysenteriae is a lactose non-fermenting, Gram-negative rod, causing dysentery. 4. Salmonella typhi, Escherichia coli, and Proteus vulgaris are lactose fermenters, so they would produce pink colonies on Endo agar. Therefore, the most likely causative agent is Shigella dysenteriae.
Question 2 of 5
A 30 year old patient consulted a doctor about having diarrhea and stomach aches for 5 days, temperature rise up to 37,50C with chills. The day before the patient was in a forest and drank some water from an open pond. He was diagnosed with amebic dysentery that was bacteriologically confirmed. Name the medication for treatment of this disease:
Correct Answer: A
Rationale: The correct answer is A: Metronidazole. Amebic dysentery is caused by the parasite Entamoeba histolytica, not a bacterium, hence antibiotics like Chloramphenicol or Phthalazole are ineffective. Metronidazole is the drug of choice for treating amebic dysentery due to its efficacy against anaerobic organisms like Entamoeba histolytica. Furasolidone is used for treating bacterial infections, not parasitic ones like amebiasis. The patient's symptoms of diarrhea, stomach aches, and a recent history of drinking water from a potentially contaminated source in the forest are indicative of a parasitic infection, supporting the choice of Metronidazole for treatment.
Question 3 of 5
Simple nutritive media are:
Correct Answer: C
Rationale: The correct answer is C, Meat-peptone agar, as it provides a simple nutritive media for bacterial growth. This agar contains meat extract and peptone, which are good sources of nutrients for bacterial growth. Glucose broth (A) is a liquid medium with glucose but lacks other essential nutrients. Ascites (serum) agar (B) is a selective medium used for detecting pathogens in clinical samples. Blood agar (D) is a differential medium used to distinguish different types of bacteria based on hemolytic reactions. Meat-peptone agar is the simplest and most general-purpose medium among the options provided.
Question 4 of 5
A child with diarrhea had stool microscopy revealing flagellated protozoa with two nuclei. What is the most likely causative agent?
Correct Answer: A
Rationale: The correct answer is A: Giardia lamblia. Giardia is a flagellated protozoa with two nuclei, causing diarrhea. It is commonly found in contaminated water sources. Entamoeba histolytica (B) causes amoebic dysentery with trophozoites in stool. Trichomonas vaginalis (C) causes sexually transmitted infections, not diarrhea. Balantidium coli (D) is a ciliated protozoa causing dysentery with ciliated trophozoites. Therefore, Giardia lamblia is the most likely causative agent in this case.
Question 5 of 5
Which bacteria is associated with the formation of dental caries (cavities)?
Correct Answer: B
Rationale: The correct answer is B: Streptococcus mutans. This bacterium is associated with the formation of dental caries due to its ability to metabolize sugars and produce acids that demineralize tooth enamel. Streptococcus pneumoniae (choice A) is not typically associated with dental caries. Bacillus anthracis (choice C) causes anthrax, not dental caries. Clostridium botulinum (choice D) causes botulism, not dental caries. Streptococcus mutans' unique characteristics make it the correct choice for the bacteria associated with dental caries.