Nokea
Ribosomes are a target for antibiotics:
- A. Aminoglycosides, tetracyclines, macrolides and lincosamides
- B. Beta-lactam antibiotics
- C. Antifolate compounds, quinolones and raspicin
- D. None of the above
Correct Answer: A
Rationale: Ribosomes are the target for antibiotics as they interfere with protein synthesis in bacteria. Aminoglycosides, tetracyclines, macrolides, and lincosamides all target ribosomes by inhibiting protein synthesis at different stages. Beta-lactam antibiotics target cell wall synthesis, not ribosomes. Antifolate compounds, quinolones, and raspicin target DNA synthesis and replication, not ribosomes. Therefore, the correct answer is A as it includes antibiotics that specifically target ribosomes for inhibiting bacterial protein synthesis.
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A patient with fever, headache, and neck stiffness had a cerebrospinal fluid sample showing Gram-negative diplococci. What is the most likely causative agent?
- A. Neisseria meningitidis
- B. Streptococcus pneumoniae
- C. Haemophilus influenzae
- D. Klebsiella pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Neisseria meningitidis. This is because Neisseria meningitidis is a Gram-negative diplococcus known to cause bacterial meningitis, presenting with fever, headache, and neck stiffness. It is a common cause of meningitis in young adults and teenagers. Streptococcus pneumoniae (B) is a Gram-positive bacteria and a common cause of bacterial pneumonia, not meningitis. Haemophilus influenzae (C) is a Gram-negative coccobacillus that can cause meningitis, but it is less common in adults. Klebsiella pneumoniae (D) is a Gram-negative bacillus known to cause pneumonia and urinary tract infections, not meningitis.
A female patient has symptoms of inflammation of urogenital tracts. A smear from the vaginal mucous membrane contained big unicellular pyriform organisms with a sharp spike on the back end of their bodies; big nucleus and undulating membrane. What protozoa were revealed in the smear?
- A. Trichomonas vaginalis
- B. Trichomonas hominis
- C. Trichomonas buccalis
- D. Trypanosoma gambiense
Correct Answer: A
Rationale: The correct answer is A: Trichomonas vaginalis. Trichomonas vaginalis is a protozoan parasite that causes trichomoniasis, a sexually transmitted infection characterized by inflammation of urogenital tracts. The description of big unicellular pyriform organisms with a sharp spike on the back end of their bodies, big nucleus, and undulating membrane matches the morphology of Trichomonas vaginalis. Trichomonas hominis and Trichomonas buccalis are different species that do not cause urogenital infections. Trypanosoma gambiense is a protozoan parasite causing African trypanosomiasis and does not match the described morphology or symptoms.
What is the function of bacterial fimbriae?
- A. Adhesion to surfaces
- B. DNA replication
- C. Protein synthesis
- D. Flagella movement
Correct Answer: A
Rationale: The correct answer is A: Adhesion to surfaces. Bacterial fimbriae are hair-like appendages that help bacteria attach to surfaces, such as host cells or medical devices. This adhesion is crucial for colonization and infection. DNA replication (B) occurs in the cell's nucleus, not on the surface. Protein synthesis (C) happens inside the cell, not on the fimbriae. Flagella movement (D) is the function of flagella, not fimbriae.
A patient with fever and sore throat had a throat culture revealing Gram-positive cocci in chains. The bacteria were catalase-negative and beta-hemolytic. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Streptococcus pneumoniae
- C. Enterococcus faecalis
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes.
1. Gram-positive cocci in chains: characteristic of Streptococcus species.
2. Catalase-negative: Streptococcus species are catalase-negative.
3. Beta-hemolytic: S. pyogenes is beta-hemolytic on blood agar.
Therefore, S. pyogenes fits all these criteria.
B: Streptococcus pneumoniae is catalase-negative but alpha-hemolytic, not beta-hemolytic.
C: Enterococcus faecalis is catalase-negative, but not typically beta-hemolytic or in chains.
D: Staphylococcus aureus is catalase-positive and not in chains.
A fecal sample from a patient with diarrhea was cultured on Endo agar, resulting in colorless colonies. The bacteria were Gram-negative rods. What microorganism is most likely?
- A. Salmonella
- B. Shigella
- C. Escherichia coli
- D. Proteus
Correct Answer: B
Rationale: The correct answer is B: Shigella. On Endo agar, Shigella appears as colorless colonies due to its inability to ferment lactose. Shigella is a Gram-negative rod and is a common cause of diarrhea. Salmonella (A) and Escherichia coli (C) would typically produce pink colonies on Endo agar as they can ferment lactose. Proteus (D) is not commonly associated with diarrhea and would not be expected to grow on Endo agar.