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A patient with acute food poisoning had fecal cultures grown on Endo agar, resulting in colorless colonies. What microorganism is most likely responsible?
- A. Salmonella
- B. Escherichia coli
- C. Staphylococcus
- D. Shigella
Correct Answer: A
Rationale: Step 1: Endo agar is a selective and differential media commonly used to isolate gram-negative bacteria.
Step 2: Colorless colonies on Endo agar indicate the absence of lactose fermentation.
Step 3: Salmonella is a gram-negative bacterium that does not ferment lactose, leading to colorless colonies on Endo agar.
Step 4: Therefore, the correct answer is A: Salmonella.
Summary:
B: Escherichia coli ferments lactose, producing pink colonies on Endo agar.
C: Staphylococcus is a gram-positive bacterium and would not grow on Endo agar.
D: Shigella is a gram-negative bacterium but ferments lactose, resulting in pink colonies on Endo agar.
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Tinea capitis is a fungal infection of the:
- A. feet
- B. scalp
- C. mouth
- D. hands
Correct Answer: B
Rationale: The correct answer is B: scalp. Tinea capitis is a fungal infection that specifically affects the scalp. This infection is caused by dermatophytes, which thrive in warm and moist environments. It typically presents with symptoms such as scaling, itching, and hair loss on the scalp. Choices A, C, and D are incorrect because tinea pedis (athlete's foot) affects the feet, oral thrush is a fungal infection of the mouth, and tinea manuum affects the hands. By process of elimination and understanding the specific characteristics of tinea capitis, we can determine that the scalp is the correct location for this fungal infection.
Risk factor for the development of infection is
- A. malignant disease
- B. cytostatic therapy
- C. premature birth
- D. all of them
Correct Answer: D
Rationale: The correct answer is D: all of them. Malignant disease weakens the immune system, making individuals more susceptible to infections. Cytostatic therapy suppresses the immune system, increasing the risk of infections. Premature birth can lead to underdeveloped immune systems, making babies more prone to infections. Therefore, all three choices are risk factors for the development of infections. Other choices are incorrect because each individual risk factor listed contributes to an increased susceptibility to infections.
Enzymatic reactions can be expressed in which of the following chemical notations?
- A. S + P = E
- B. P + P = E
- C. E + S = P
- D. S + S = P
Correct Answer: C
Rationale: The correct answer is C: E + S = P. This notation represents the interaction between an enzyme (E) and a substrate (S) resulting in a product (P). Enzymes facilitate chemical reactions by binding to substrates and converting them into products. Choice A is incorrect because it does not include the enzyme in the reaction. Choice B is incorrect as it involves two substrates binding to the enzyme, not a substrate converting to a product. Choice D is incorrect as it shows two substrates reacting to form a product without involvement of an enzyme. Thus, choice C accurately represents the process of enzymatic reactions involving enzymes, substrates, and products.
The relations between the macroorganism and the resident skin microflora are defined as:
- A. Commensalism
- B. Infection
- C. Parasitism
- D. No correct answer
Correct Answer: A
Rationale: The correct answer is A: Commensalism. In this relationship, the skin microflora benefits from the host without causing harm or benefitting it. This is evident in the mutualistic interaction where the microflora receive nutrients and a place to live, while the host remains unaffected. Choice B, Infection, is incorrect because it implies harm to the host. Choice C, Parasitism, is also incorrect as it involves one organism benefiting at the expense of the other. Choice D, No correct answer, is not applicable here as Commensalism accurately describes the relationship between the macroorganism and skin microflora.
In which of the following cases of immune reactions a large lattice is formed?
- A. Antibody is in excess
- B. Antigens and antibodies are in optimal proportion
- C. Antigen is in excess
- D. None of the above
Correct Answer: B
Rationale: The correct answer is B because in immune reactions, a large lattice is formed when antigens and antibodies are in optimal proportion. This optimal ratio allows for the formation of a strong antigen-antibody complex, leading to the aggregation of immune complexes into large lattice structures. When antibodies are in excess (choice A), there may not be enough antigens to form a stable lattice. Similarly, when antigens are in excess (choice C), there may be insufficient antibodies to form a strong lattice. Choice D is incorrect because the optimal proportion of antigens and antibodies is crucial for the formation of large lattices in immune reactions.