Nokea
The biosafety level necessary in water testing facilities is level
- A. 1
- B. 2
- C. 3
- D. 4
Correct Answer: A
Rationale: The correct answer is A: 1. Water testing facilities typically handle low-risk microorganisms, hence requiring Biosafety Level 1. BSL 1 is suitable for working with well-characterized agents not known to consistently cause disease in healthy adults. BSL 2 is for moderate-risk agents, BSL 3 for high-risk agents, and BSL 4 for dangerous pathogens. Therefore, choices B, C, and D are incorrect for water testing facilities due to the low risk involved in handling the microorganisms found in water samples.
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A patient presents with diarrhea and dehydration. A fecal smear stained by Gram's method revealed Gram-negative, comma-shaped bacteria. What is the causative agent?
- A. Vibrio cholerae
- B. Salmonella typhi
- C. Shigella dysenteriae
- D. Escherichia coli
Correct Answer: A
Rationale: The correct answer is A: Vibrio cholerae. Vibrio cholerae is the causative agent of cholera, which presents with severe watery diarrhea leading to dehydration. The characteristic comma-shaped (curved rod) appearance of Gram-negative bacteria is typical of Vibrio cholerae. This bacterium produces the cholera toxin, leading to the excessive secretion of fluid into the intestines. Salmonella typhi causes typhoid fever with symptoms like sustained fever, not watery diarrhea. Shigella dysenteriae causes bloody diarrhea and abdominal cramps. Escherichia coli can cause various types of infections, but typically not severe watery diarrhea like cholera.
Hepatitis B infection may present with:
- A. Jaundice
- B. Elevated serum aminotransferase levels
- C. No symptoms
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D: All of the above. Hepatitis B infection can present with jaundice due to liver inflammation, elevated serum aminotransferase levels due to liver damage, and sometimes no symptoms in the acute phase. This comprehensive presentation covers the spectrum of possible clinical manifestations of hepatitis B infection. Choices A and B are correct as they are common manifestations of hepatitis B infection. Choice C is incorrect as hepatitis B infection can indeed present with symptoms, making option D the most appropriate choice.
Which of the following bacteria produce toxins that can cause severe gastrointestinal illness?
- A. Vibrio cholerae
- B. Clostridium difficile
- C. Escherichia coli
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D, "All of the above," because all three bacteria listed (Vibrio cholerae, Clostridium difficile, Escherichia coli) produce toxins that can cause severe gastrointestinal illness. Vibrio cholerae produces cholera toxin leading to severe diarrhea. Clostridium difficile produces toxins causing antibiotic-associated diarrhea. Escherichia coli can produce toxins such as Shiga toxin causing severe gastrointestinal symptoms. Therefore, all the options listed are correct in producing toxins that can result in severe gastrointestinal illness.
A patient with diarrhea had fecal analysis revealing small, curved Gram-negative bacilli with a monotrichous flagellum. These bacteria do not form spores or capsules and thrive in alkaline conditions. What is the causative agent?
- A. Vibrio cholerae
- B. Escherichia coli
- C. Salmonella
- D. Shigella
Correct Answer: A
Rationale: Step 1: Small, curved Gram-negative bacilli with a monotrichous flagellum point towards a motile bacterium.
Step 2: The absence of spores or capsules and preference for alkaline conditions further narrows down the possibilities.
Step 3: Vibrio cholerae fits all criteria as it is a curved, motile, Gram-negative bacillus that thrives in alkaline environments.
Summary: Escherichia coli is a facultative anaerobe, Salmonella and Shigella are non-flagellated, and all of them can form capsules or spores, unlike Vibrio cholerae.
Your patient is a 22-year-old man. The patient reports that two weeks after unprotected sexual contact, a small ulcer appeared on its penis. The local inguinal lymph nodes are enlarged. Dark field microscopic examination of the ulcer secretions was performed. The test reveals presence of motile, curved spirochete. The most common causative agent of the disease is:
- A. Chlamydia trachoma's
- B. Treponema pallidum
- C. Neisseria gonorrhoeae
- D. Herpes simplex virus, type 2
Correct Answer: B
Rationale: The correct answer is B: Treponema pallidum. The scenario describes symptoms of primary syphilis, which is caused by Treponema pallidum. The presence of a painless ulcer (chancre) and enlarged inguinal lymph nodes are characteristic of syphilis. Dark field microscopic examination showing motile, curved spirochetes is highly specific for Treponema pallidum.
Incorrect explanations:
A: Chlamydia trachomatis typically causes urethritis or cervicitis, not painless ulcers.
C: Neisseria gonorrhoeae causes gonorrhea, which presents with purulent discharge, not painless ulcers.
D: Herpes simplex virus type 2 causes genital herpes, leading to painful ulcers and vesicles, not painless ulcers seen in syphilis.