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A patient with a deep tissue infection had a wound culture revealing Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-negative. What is the most likely causative agent?
- A. Staphylococcus epidermidis
- B. Staphylococcus aureus
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus epidermidis. The presence of Gram-positive cocci in clusters that are catalase-positive and coagulase-negative points towards coagulase-negative staphylococci like Staphylococcus epidermidis. Staphylococcus aureus is catalase-positive and coagulase-positive. Streptococcus pyogenes is catalase-negative. Enterococcus faecalis is catalase-negative and not typically seen in clusters. Therefore, the most likely causative agent in this scenario is Staphylococcus epidermidis.
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The First-line tuberculosis drugs include:
- A. Isoniazid and rifampicin
- B. Penicillin and erythromycin
- C. Trimethoprim and third generation cephalosporins
- D. All the listed above can be used depending on their resistance profile
Correct Answer: A
Rationale: The correct answer is A: Isoniazid and rifampicin. These drugs are considered first-line treatment for tuberculosis due to their high efficacy and low toxicity. Isoniazid targets the cell wall of the tuberculosis bacteria, while rifampicin inhibits RNA synthesis. They are recommended by WHO as the first choice for treating tuberculosis.
Choice B (Penicillin and erythromycin) is incorrect because these antibiotics are not effective against tuberculosis bacteria.
Choice C (Trimethoprim and third generation cephalosporins) is incorrect because they are not considered first-line drugs for tuberculosis treatment.
Choice D (All the listed above can be used depending on their resistance profile) is incorrect because only isoniazid and rifampicin are universally recognized as first-line drugs for tuberculosis regardless of resistance profile.
Which bacterial structure helps in the movement towards or away from chemical stimuli?
- A. Flagella
- B. Pili
- C. Capsule
- D. Fimbriae
Correct Answer: A
Rationale: Flagella are the correct answer because they are long, whip-like structures that aid in bacterial movement towards or away from chemical stimuli. They rotate like propellers, allowing the bacterium to navigate its environment. Pili are used for attachment, not movement. Capsules are involved in protection and adherence, not chemotaxis. Fimbriae help in attachment to surfaces, not in movement towards stimuli.
Which bacteria are known for producing toxins that can lead to foodborne illnesses?
- A. Clostridium botulinum
- B. Salmonella enterica
- C. Escherichia coli
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D because all three bacteria (Clostridium botulinum, Salmonella enterica, Escherich:ia coli) are known to produce toxins causing foodborne illnesses. Clostridium botulinum produces botulinum toxin, causing botulism. Salmonella enterica produces toxins leading to salmonellosis. Escherichia coli can produce toxins like Shiga toxin causing food poisoning. Choices A, B, and C are incorrect because each bacterium is individually known to produce toxins causing foodborne illnesses, thus the correct answer is D.
Algae that contain agar in their cell walls belong to:
- A. Chrysophyta
- B. Rhodophyta
- C. Chlorophyta
- D. Phaeophyta
Correct Answer: B
Rationale: The correct answer is B: Rhodophyta. Rhodophyta is the phylum of red algae, which are known to contain agar in their cell walls. Agar is a gelatinous substance derived from these algae. Chrysophyta (A), Chlorophyta (C), and Phaeophyta (D) do not typically contain agar in their cell walls. Chrysophyta includes diatoms, Chlorophyta includes green algae, and Phaeophyta includes brown algae, none of which are known for agar production. Therefore, Rhodophyta is the correct choice based on the presence of agar in their cell walls.
A female who had been continuously taking antibiotics for an intestinal infection developed a complication manifested by inflammation of the oral mucosa and white deposit. Bacteriological study of the deposit samples revealed yeast fungi Candida albicans. Which of the following medications is indicated for the treatment of this complication?
- A. Fluconazole
- B. Biseptol
- C. Tetracycline
- D. Furazolidone
Correct Answer: A
Rationale: Rationale for Correct Answer (A: Fluconazole): Fluconazole is an antifungal medication used to treat yeast infections caused by Candida albicans. It targets the fungal cell membrane, disrupting its structure and function. This makes it an effective treatment for oral thrush, which is caused by Candida overgrowth in the oral mucosa. The continuous use of antibiotics can disrupt the normal balance of microorganisms in the body, leading to fungal overgrowth. Fluconazole specifically targets the yeast fungi without affecting bacteria, making it the appropriate choice for this complication.
Summary of Incorrect Choices:
B: Biseptol - Biseptol is an antibiotic that targets bacteria, not fungi like Candida albicans.
C: Tetracycline - Tetracycline is also an antibiotic that targets bacteria, not fungi.
D: Furazolidone - Furazolidone is an antibiotic primarily used for treating bacterial infections, not fungal infections like oral thrush caused by Candida