Nokea
Formic acid is a fermentation product of
- A. Streptococcus.
- B. Klebsiella.
- C. Clostridium.
- D. Actinomyces.
Correct Answer: D
Rationale: Step 1: Formic acid is produced during fermentation by Actinomyces.
Step 2: Actinomyces are known to produce organic acids like formic acid through fermentation.
Step 3: Other choices like Streptococcus, Klebsiella, and Clostridium are not typically associated with formic acid production.
Step 4: Actinomyces is the most likely candidate based on its fermentation capabilities.
Summary: Actinomyces is the correct answer because it is known to produce formic acid during fermentation, while the other choices lack this specific metabolic function.
You may also like to solve these questions
A 25-year-old patient reports pain, burning at urination and scarce secretion in the morning. Urine samples are taken and cultivated on blood and MacConkey agar. After 24 hours of incubation, the culture are sterile. Which one of the following bacteria is the most probable cause of this disease?
- A. Escherichia coli
- B. Chlamydia trachomatis
- C. Streptococcus pneumoniae
- D. Neisseria gonorrhoeae
Correct Answer: B
Rationale: The correct answer is B: Chlamydia trachomatis. This is because Chlamydia trachomatis is an obligate intracellular bacterium that cannot be cultured on standard agar plates. The symptoms described by the patient, such as pain, burning at urination, and scarce secretion in the morning, are indicative of a possible chlamydial infection. Additionally, the fact that the urine cultures are sterile after 24 hours of incubation suggests that the causative agent is not a typical bacteria like Escherichia coli, Streptococcus pneumoniae, or Neisseria gonorrhoeae, which would normally grow on agar plates. Therefore, Chlamydia trachomatis is the most probable cause of this disease.
Summary:
A: Escherichia coli - Incorrect, as it is a common cause of urinary tract infections and would typically grow on agar plates.
C: Streptococcus pneumoniae - Incorrect, as it is
What reaction is catalyzed by a beta-lactamase enzyme
- A. the final cross-linking reaction to form the bacterial cell wall
- B. the biosynthesis of the penicillin structure from the amino acid valine and cysteine
- C. the hydrolysis of the four-membered ring present in penicillin
- D. the hydrolysis of the acyl side chain from penicillin structures
Correct Answer: C
Rationale: The correct answer is C: the hydrolysis of the four-membered ring present in penicillin. Beta-lactamase enzyme catalyzes the hydrolysis of the four-membered beta-lactam ring present in penicillin, rendering the antibiotic ineffective against bacterial cell walls. This enzyme breaks the bond in the beta-lactam ring, thus inactivating the antibiotic.
Incorrect choices:
A: the final cross-linking reaction to form the bacterial cell wall - This is incorrect as beta-lactamase does not participate in the formation of bacterial cell walls.
B: the biosynthesis of the penicillin structure from the amino acid valine and cysteine - This is incorrect as beta-lactamase is not involved in the biosynthesis of penicillin.
D: the hydrolysis of the acyl side chain from penicillin structures - This is incorrect as beta-lactamase specifically targets the beta-lactam ring, not the
A patient with a sore throat had a throat culture revealing Gram-positive cocci in chains. The bacteria were catalase-negative and beta-hemolytic on blood agar. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Streptococcus pneumoniae
- D. Enterococcus faecalis
Correct Answer: A
Rationale: Step 1: Gram-positive cocci in chains suggest Streptococcus species.
Step 2: Catalase-negative eliminates Staphylococcus aureus.
Step 3: Beta-hemolytic on blood agar matches Streptococcus pyogenes.
Step 4: Streptococcus pyogenes is a common cause of sore throat (pharyngitis).
Summary:
A: Streptococcus pyogenes - Correct due to Gram-positive cocci in chains, catalase-negative, beta-hemolytic, and common cause of sore throat.
B: Staphylococcus aureus - Incorrect due to catalase-positive.
C: Streptococcus pneumoniae - Incorrect due to alpha-hemolytic.
D: Enterococcus faecalis - Incorrect due to not being beta-hemolytic.
Which bacteria are capable of producing endospores?
- A. Staphylococcus aureus
- B. Clostridium botulinum
- C. Escherichia coli
- D. Neisseria gonorrhoeae
Correct Answer: B
Rationale: The correct answer is B: Clostridium botulinum. This bacterium belongs to the Clostridium genus, known for its ability to produce endospores. Endospores are dormant, resistant structures that help bacteria survive harsh conditions. Staphylococcus aureus (A), Escherichia coli (C), and Neisseria gonorrhoeae (D) do not produce endospores. Staphylococcus aureus is a gram-positive bacterium known for causing various infections, but it does not form endospores. Escherichia coli is a gram-negative bacterium commonly found in the intestines of humans and animals, but it does not produce endospores. Neisseria gonorrhoeae is a gram-negative bacterium that causes the sexually transmitted infection gonorrhea, but it also does not form endospores.
A large-scale reaction with parapertussis and pertussis diagnosticums was made in order to make serological diagnostics of the whooping cough. At the bottom of the test-tubes with diagnosticum of Bordetella parapertussis a granular sediment formed. What antibodies did this reaction reveal?
- A. Agglutinins
- B. Precipitins
- C. Opsonins
- D. Bacteriolysins
Correct Answer: B
Rationale: The correct answer is B: Precipitins. When a granular sediment forms at the bottom of the test-tubes, it indicates the formation of antigen-antibody complexes that are insoluble and precipitate out of the solution. Precipitins are antibodies that specifically react with antigens to form insoluble complexes. Agglutinins cause clumping of cells, opsonins enhance phagocytosis, and bacteriolysins lyse bacteria. These processes do not result in the formation of a granular sediment, making them incorrect choices in this context.