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A patient with pneumonia had a sputum culture revealing Gram-positive diplococci. The bacteria were catalase-negative and alpha-hemolytic. What is the most likely causative agent?
- A. Streptococcus pneumoniae
- B. Staphylococcus aureus
- C. Neisseria meningitidis
- D. Klebsiella pneumoniae
Correct Answer: A
Rationale: Step 1: Gram-positive diplococci suggest a pneumococcal infection.
Step 2: Catalase-negative indicates Streptococcus.
Step 3: Alpha-hemolysis matches S. pneumoniae's characteristics.
Therefore, Streptococcus pneumoniae is the most likely causative agent. Staphylococcus aureus (B) is catalase-positive, Neisseria meningitidis (C) is Gram-negative, and Klebsiella pneumoniae (D) is not diplococci or alpha-hemolytic.
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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.
Which toxin is specific for ETEC:
- A. TSST-1
- B. Shiga-like toxin
- C. Erythrogenic toxin
- D. LT enterotoxin
Correct Answer: D
Rationale: The correct answer is D: LT enterotoxin. This toxin is specific for Enterotoxigenic E. coli (ETEC) and is responsible for causing diarrhea by increasing cyclic AMP levels in intestinal cells. TSST-1 (choice A) is produced by Staphylococcus aureus, not ETEC. Shiga-like toxin (choice B) is produced by Shigella and EHEC, not ETEC. Erythrogenic toxin (choice C) is produced by Streptococcus pyogenes, not ETEC. Therefore, the LT enterotoxin is the specific toxin associated with ETEC.
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.
The bacterial component targeted by penicillin is:
- A. DNA
- B. Plasma membrane
- C. Cell wall
- D. Ribosomes
Correct Answer: C
Rationale: The correct answer is C: Cell wall. Penicillin targets the cell wall of bacteria by inhibiting the formation of peptidoglycan, a crucial component of the cell wall. This weakens the cell wall, leading to bacterial cell lysis. Choice A (DNA) is incorrect because penicillin does not directly target DNA. Choice B (Plasma membrane) is incorrect as penicillin primarily affects the cell wall, not the plasma membrane. Choice D (Ribosomes) is incorrect because penicillin does not target bacterial ribosomes, which are involved in protein synthesis.
For treatment of Anthrax are used
- A. Penicillins, tetracyclins, macrolides
- B. anti-anthrax gamma-globulins
- C. anti-anthrax immune-serum
- D. all of the above
Correct Answer: D
Rationale: The correct answer is D because the treatment for Anthrax involves using antibiotics such as penicillins, tetracyclines, and macrolides to target the bacteria. Anti-anthrax gamma-globulins and immune-serum are used to provide passive immunity, but they are not the primary treatment. Therefore, options A, B, and C are incorrect as they do not encompass all the necessary components for treating Anthrax. Overall, using a combination of antibiotics and immune-based treatments like gamma-globulins and immune-serum provides a comprehensive approach to managing Anthrax infection.