Nokea
A wound infection culture revealed Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-positive. What is the most likely causative agent?
- A. Staphylococcus aureus
- B. Staphylococcus epidermidis
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus aureus. This bacterium is characterized by Gram-positive cocci in clusters, catalase-positive, and coagulase-positive. Staphylococcus aureus is a common pathogen causing wound infections due to its ability to produce toxins and enzymes. Staphylococcus epidermidis (B) is catalase-positive but coagulase-negative, making it less likely to cause infections. Streptococcus pyogenes (C) is catalase-negative and typically causes streptococcal infections, not wound infections. Enterococcus faecalis (D) is catalase-negative and typically associated with urinary tract infections. Thus, Staphylococcus aureus is the most likely causative agent based on the given characteristics.
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A veterenary attendant working at a cattle farm complains of joint pain, fever, indisposition and sweating at nighttime that he has been experiencing for a month. Giving the regard to such presentations and occupational history the doctor suspected brucellosis. What material taken from this patient is to be analyzed in a common microbiological laboratory?
- A. Blood serum
- B. Spinal fluid
- C. Vomit mass
- D. Urine
Correct Answer: A
Rationale: The correct answer is A: Blood serum. In suspected cases of brucellosis, blood serum is typically analyzed in a common microbiological laboratory. This is because the bacteria causing brucellosis, Brucella species, can be detected through serological tests in the blood serum. The presence of specific antibodies against Brucella in the serum confirms the diagnosis. Spinal fluid (choice B) would be analyzed in cases of suspected central nervous system infections, which are not typical for brucellosis. Vomit mass (choice C) is not a common sample for microbiological analysis in cases of brucellosis. Urine (choice D) is not the preferred sample for detecting Brucella antibodies; blood serum is the primary choice for serological testing.
There is/are __________ level(s) of biosafety depending on the organisms handled.
- A. 1
- B. 2
- C. 3
- D. 4
Correct Answer: D
Rationale: The correct answer is D (4) because biosafety levels range from 1 to 4, each corresponding to the level of containment required when handling different types of organisms. BSL-1 is for low-risk agents, while BSL-4 is for dangerous pathogens. Choice A (1) is incorrect as there are multiple levels, not just one. Choice B (2) and C (3) are incorrect as they do not account for all the levels of biosafety required for handling various organisms. Therefore, D is the correct answer as it encompasses the full range of biosafety levels.
The growth phase in which bacteria adapt to the conditions of cultivation is called:
- A. Stationary phase
- B. Log phase
- C. Lag phase
- D. Death phase
Correct Answer: C
Rationale: The correct answer is C: Lag phase. During the lag phase, bacteria adapt to the new environment before starting to grow and divide. This phase is characterized by a period of low growth as bacteria adjust their metabolism to the available nutrients. The stationary phase (A) is when growth rate equals death rate, the log phase (B) is rapid exponential growth, and the death phase (D) is when cells start to die due to nutrient depletion or accumulation of waste products. Thus, the lag phase is the initial phase where bacteria prepare for growth, making it the correct answer.
For shigella is true:
- A. They produce hydrogen sulfide
- B. They ferment lactose
- C. They are nonmotile
- D. All of them are mannitol positive
Correct Answer: C
Rationale: Step-by-step rationale:
1. Shigella is a nonmotile bacterium.
2. This lack of motility is a key characteristic used to differentiate it from other enteric bacteria.
3. Nonmotile nature of Shigella helps it to cause infections by invading the intestinal epithelial cells.
4. Therefore, choice C is correct as Shigella is indeed nonmotile.
Summary:
A: Incorrect - Shigella does not produce hydrogen sulfide.
B: Incorrect - Shigella does not ferment lactose.
D: Incorrect - Shigella is not mannitol positive.
A man is ill with a protozoan disease characterized by cerebral affection and loss of sight. Blood analysis revealed halfmoon-shaped unicellular organisms with pointed ends. This disease is caused by:
- A. Toxoplasma B.Leishmania C.Lamblia D.Amoeba E.Trichomonad
Correct Answer: A
Rationale: The correct answer is A: Toxoplasma. Toxoplasma gondii causes Toxoplasmosis, a protozoan disease that can affect the brain and lead to vision loss. The halfmoon-shaped unicellular organisms with pointed ends described in the blood analysis are characteristic of Toxoplasma parasites. Toxoplasma infection commonly occurs through ingestion of contaminated food or water, or contact with infected cat feces. Leishmania causes Leishmaniasis, Lamblia causes Giardiasis, Amoeba causes Amebiasis, and Trichomonad causes Trichomoniasis, none of which match the symptoms and blood analysis findings described in the question.