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A patient with diarrhea had stool culture revealing non-lactose-fermenting, Gram-negative rods. The bacteria produced gas in a nutrient broth. What is the most likely causative agent?
- A. Salmonella typhi
- B. Shigella dysenteriae
- C. Escherichia coli
- D. Proteus vulgaris
Correct Answer: D
Rationale: The correct answer is D: Proteus vulgaris. Non-lactose-fermenting, Gram-negative rods that produce gas in a nutrient broth are characteristic of Proteus species. Proteus vulgaris is known for its swarming motility and ability to produce hydrogen sulfide gas. Salmonella typhi and Shigella dysenteriae are Enterobacteriaceae that do not produce gas in a nutrient broth. Escherichia coli is a lactose-fermenting bacterium and would not be expected to produce gas in a nutrient broth.
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The basic requirements of PCR reaction include:
- A. DNA segment to be amplified
- B. Two oligonucleotide primers
- C. Heat stable DNA
- D. All of these
Correct Answer: D
Rationale: The correct answer is D because all the options are essential for a PCR reaction.
A: DNA segment is required as the template for amplification.
B: Two oligonucleotide primers are needed to initiate DNA replication.
C: Heat stable DNA polymerase (not just heat stable DNA) is crucial for withstanding the high temperatures during PCR.
In summary, without any of these components, the PCR reaction cannot proceed effectively.
The primary stage of syphilis is usually manifested as:
- A. Diffuse maculopapular rush
- B. Purulent exudation from the urethra
- C. Syphilitic granulomas (gummas)
- D. Non-tender chancre (ulcus durum)
Correct Answer: D
Rationale: The correct answer is D: Non-tender chancre (ulcus durum). In the primary stage of syphilis, an individual typically develops a painless ulcer known as a chancre at the site of infection. This ulcer is usually firm, round, and clean with well-defined borders. It is important to note that it is non-tender, which distinguishes it from other skin conditions. This characteristic helps healthcare providers differentiate syphilis from other sexually transmitted infections.
Explanation for other choices:
A: Diffuse maculopapular rash - This is more commonly associated with secondary syphilis.
B: Purulent exudation from the urethra - This is not a typical presentation of primary syphilis.
C: Syphilitic granulomas (gummas) - Gummas typically develop in the tertiary stage of syphilis, not in the primary stage.
Sanitary and bacteriological examination of air in drug-store premises revealed increased content of sanitary representative microorganisms. What microorganisms are these?
- A. Golden staphylococcus and hemolytic streptococcus
- B. Diphtheria and tuberculosis bacilli
- C. Colon and blue pus bacilli
- D. Epidermal staphylococcus and sarcina
Correct Answer: A
Rationale: The correct answer is A (Golden staphylococcus and hemolytic streptococcus) because these microorganisms are commonly found in the air of contaminated environments like drug-store premises. Golden staphylococcus and hemolytic streptococcus are pathogenic bacteria associated with infections in humans, indicating poor sanitation. The other choices are incorrect because:
B: Diphtheria and tuberculosis bacilli are not commonly found in the air in drug-store premises.
C: Colon and blue pus bacilli are not typical microorganisms associated with air contamination.
D: Epidermal staphylococcus and sarcina are not likely to be present in high amounts in the air of drug-store premises.
Micellar growth
- A. is observed in bacterial cells
- B. includes a parent and daughter cell which have different sizes
- C. is inherent in viruses and rickettsia
- D. represents apical prolongation of the hyphae in the fungus
Correct Answer: D
Rationale: Step 1: Micellar growth refers to the apical prolongation of hyphae in fungi.
Step 2: Fungi have a unique growth structure with hyphae extending at the tips.
Step 3: This growth pattern allows fungi to expand and access nutrients.
Step 4: Bacterial cells (A) do not exhibit micellar growth.
Step 5: Parent and daughter cells in division have similar sizes, not different (B).
Step 6: Viruses and rickettsia (C) do not display micellar growth.
The drug most often used in fighting protozoan infections of the reproductive system is:
- A. ampicillin
- B. tetracycline
- C. ciprofloxacin
- D. metronidazole
Correct Answer: D
Rationale: The correct answer is D: metronidazole. Metronidazole is specifically effective against protozoan infections due to its ability to target and disrupt the DNA of the parasites. It is commonly used to treat infections such as trichomoniasis and giardiasis that affect the reproductive system. Ampicillin (A) and tetracycline (B) are antibiotics that target bacteria, not protozoa. Ciprofloxacin (C) is also an antibiotic that is effective against certain bacterial infections but not protozoan infections. Therefore, metronidazole is the most appropriate choice for fighting protozoan infections of the reproductive system.