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What is the name of the enzyme that allows the bacteria to become resistant to most penicillins?
- A. Beta lactam ring
- B. MRSA
- C. Beta lactamase
- D. Aminoglycoside ring
Correct Answer: C
Rationale: The correct answer is C: Beta lactamase. This enzyme is produced by bacteria to break down the beta-lactam ring structure of penicillins, rendering them ineffective. Beta lactam ring (A) is part of the penicillin molecule, not an enzyme. MRSA (B) stands for methicillin-resistant Staphylococcus aureus, a type of bacteria resistant to certain antibiotics, not an enzyme. Aminoglycoside ring (D) refers to a different class of antibiotics and is not related to penicillin resistance in bacteria.
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A specimen stained by Ozheshko method contains rod-like microorganisms stained blue with round terminal components stained red. What are these components called?
- A. Spores
- B. Cilia
- C. Flagella
- D. Capsules
Correct Answer: A
Rationale: The correct answer is A: Spores. In the Ozheshko staining method, spores appear blue with red terminal components. Spores are reproductive structures produced by some bacteria, fungi, and protozoa. Cilia are short, hair-like structures used for movement. Flagella are long, whip-like structures also used for movement. Capsules are outer protective layers surrounding some bacteria. In this case, the description of rod-like microorganisms with blue staining and red terminal components aligns with the characteristics of spores, making it the correct answer.
The effect of which of the following toxins DOES NOT MANIFEST with neurological symptoms:
- A. Tetanospasmin
- B. Diphtheria exotoxin
- C. Botulinum exotoxin
- D. Pertussis exotoxin
Correct Answer: D
Rationale: Certainly! The correct answer is D: Pertussis exotoxin. Pertussis toxin primarily affects the respiratory system causing whooping cough. It does not directly target the nervous system like the other toxins listed. Tetanospasmin causes muscle spasms, Diphtheria exotoxin affects the heart and nerves, and Botulinum exotoxin causes paralysis by blocking neurotransmitter release. Therefore, Pertussis exotoxin is the only toxin among the options that does not manifest with neurological symptoms.
Natural reservoirs of legionellae are:
- A. Water, soil, mud
- B. Only infected humans
- C. Infected animals and humans
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A because Legionellae are typically found in natural water sources such as lakes, rivers, and soil. Legionellae thrive in aquatic environments and can also be present in mud. Choice B is incorrect as Legionellae are not limited to infected humans but are also found in the natural environment. Choice C is incorrect as Legionellae are not primarily associated with infected animals. Choice D is incorrect as Legionellae do have natural reservoirs in water and soil.
A patient complains of acute spastic abdominal pain, frequent urge to defecate, liquid bloody feces with mucus. Laboratory analysis of fecal smear revealed inconstant in shape organisms with erythrocyte. What is the most likely diagnosis?
- A. Amebiasis.
- B. Lambliasis.
- C. Schistosomiasis.
- D. Intestinal trichomoniasis.
Correct Answer: A
Rationale: The correct answer is A: Amebiasis. Amebiasis is caused by the parasite Entamoeba histolytica, presenting with symptoms like acute abdominal pain, bloody diarrhea with mucus, and inconstant shape organisms seen in fecal smear. The presence of erythrocytes supports the diagnosis due to the parasite's ability to invade intestinal mucosa causing bleeding. Choice B (Lambliasis) presents with different symptoms like steatorrhea and fatigue. Choice C (Schistosomiasis) is mainly associated with liver and urinary symptoms. Choice D (Intestinal trichomoniasis) commonly presents with watery diarrhea and does not typically cause bloody stools. Therefore, based on the patient's symptoms and fecal smear findings, Amebiasis is the most likely diagnosis.
A bacteriological laboratory has been investigating a sample of homemade dried fish that was the cause of severe food poisoning. Microscopy of the culture inoculated in Kitt-Tarozzi medium revealed microorganisms resembling a tennis racket. What diagnosis can be made?
- A. Botulism
- B. Salmonellosis
- C. Cholera
- D. Dysentery
Correct Answer: A
Rationale: The correct answer is A: Botulism. The tennis racket appearance seen under the microscope is characteristic of Clostridium botulinum, the bacterium responsible for botulism. This bacterium produces spores that resemble a tennis racket shape. Botulism is a type of food poisoning caused by the ingestion of the toxin produced by Clostridium botulinum.
Summary:
B: Salmonellosis is caused by Salmonella bacteria, which do not exhibit a tennis racket appearance.
C: Cholera is caused by Vibrio cholerae, which also does not resemble a tennis racket under the microscope.
D: Dysentery is typically caused by bacteria such as Shigella or Entamoeba histolytica, neither of which exhibit the characteristic tennis racket appearance.