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A patient with chronic diarrhea had stool microscopy revealing flagellated protozoa with two nuclei. What is the most likely causative agent?
- A. Giardia lamblia
- B. Entamoeba histolytica
- C. Trichomonas vaginalis
- D. Balantidium coli
Correct Answer: A
Rationale: The correct answer is A: Giardia lamblia. Giardia lamblia is a flagellated protozoan with two nuclei found in the stool. It commonly causes chronic diarrhea. The other choices are incorrect because B: Entamoeba histolytica causes dysentery, not chronic diarrhea; C: Trichomonas vaginalis is a sexually transmitted infection, not typically found in stool; D: Balantidium coli is a ciliated protozoan, not flagellated.
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Bacteria that use organic compounds as the source of both carbon and energy are referred to as:
- A. photoautotrophs
- B. chemoautotrophs
- C. photoheterotrophs
- D. chemoheterotrophs
Correct Answer: D
Rationale: The correct answer is D: chemoheterotrophs. Chemoheterotrophs use organic compounds as both their carbon source and energy source. They obtain energy by breaking down organic molecules through cellular respiration. Photoautotrophs (A) use light energy to produce organic compounds, chemoautotrophs (B) use inorganic compounds for energy, and photoheterotrophs (C) use light energy but require organic compounds as a carbon source. Therefore, chemoheterotrophs best describe bacteria that obtain both carbon and energy from organic compounds.
Gram-negative, capsulated bacteria with capsule, lactose-positive colonies. Isolated for the first time in pneumonia, but have more important role in urinary infections, otitis, meningitides, sepsis, nosocomial infections:
- A. Staphylococcus aureus
- B. Klebsiella pneumonia
- C. Streptococcus pneumoniae
- D. Mycobacterium tuberculosis
Correct Answer: B
Rationale: The correct answer is B: Klebsiella pneumoniae. This bacterium is gram-negative, capsulated, and forms lactose-positive colonies. It was first isolated in pneumonia but is more commonly associated with urinary infections, otitis, meningitides, sepsis, and nosocomial infections. Klebsiella pneumoniae fits all the characteristics mentioned in the question, making it the correct choice.
Incorrect choices:
A: Staphylococcus aureus is gram-positive and does not have a capsule.
C: Streptococcus pneumoniae is also gram-positive and does not fit the description given.
D: Mycobacterium tuberculosis is an acid-fast bacterium associated with tuberculosis, but it is neither gram-negative nor lactose-positive.
The generation time of Escherichia Coli is:
- A. 20 minutes
- B. 60 minutes
- C. 20 hours
- D. 24 hours
Correct Answer: A
Rationale: The correct answer is A: 20 minutes. Escherichia coli has a short generation time, typically around 20 minutes. This means that under ideal conditions, one bacterium can divide and produce two daughter cells every 20 minutes. This rapid growth rate is a characteristic of E. coli and is important in various fields such as microbiology and biotechnology. Choice B (60 minutes) and Choice C (20 hours) are incorrect as they do not align with the typical generation time of E. coli. Choice D (24 hours) is also incorrect as it is too long for the generation time of E. coli.
Botulism agent causes severe food toxicoinfection. Point out the most characteristic morphologic feature of botulism agent.
- A. Gram-positive spore-forming bacilli with subterminal spore
- B. Thick gram-positive non-sporeforming bacilli
- C. Gram-positive spore-forming bacilli with terminal spore
- D. Thin mobile spore-forming bacilli with central spore
Correct Answer: B
Rationale: The correct answer is B: Thick gram-positive non-sporeforming bacilli. In botulism, the causative agent, Clostridium botulinum, is a thick gram-positive bacilli that does not form spores. This is a key characteristic morphologic feature.
A: Gram-positive spore-forming bacilli with subterminal spore - This is incorrect as Clostridium botulinum does not have subterminal spores.
C: Gram-positive spore-forming bacilli with terminal spore - Incorrect because Clostridium botulinum does not form spores.
D: Thin mobile spore-forming bacilli with central spore - Incorrect because Clostridium botulinum is not thin, mobile, or spore-forming.
In summary, the most characteristic morphologic feature of the botulism agent is being thick, gram-positive, and non-sporeforming, making choice B the correct answer.
A 32-year-old patient undergoing dental examination was found to have some rash-like lesions resembling secondary syphilis in the oral cavity. The patient was referred for the serological study with the purpose of diagnosis confirmation. In order to detect antibodies in the serum, living Treponema were used as diagnosticum. What serological test was performed?
- A. Immobilization
- B. Passive hemagglutination
- C. Precipitation
- D. Complement binding
Correct Answer: B
Rationale: The correct answer is B: Passive hemagglutination. In this test, red blood cells coated with Treponema antigens agglutinate in the presence of patient's serum antibodies. This indicates the presence of antibodies against Treponema, confirming the diagnosis.
A: Immobilization test uses live Treponema to detect specific antibodies, but it is not commonly used for syphilis diagnosis.
C: Precipitation test is not commonly used for syphilis diagnosis.
D: Complement binding test is not specific for syphilis and is used more for autoimmune diseases.
Therefore, passive hemagglutination is the most appropriate serological test in this case due to its specificity and relevance to the presentation of the patient.