A patient has been suffering from elevated temperature and attacks of typical cough for 10 days. Doctor administered inoculation of mucus from the patient's nasopharynx on the agar. What microorganism is presumed?

Correct Answer: A

Rationale: The correct answer is A: Pertussis bacillus. The symptoms described - elevated temperature and typical cough - are indicative of whooping cough, caused by Bordetella pertussis. By inoculating mucus from the nasopharynx on agar, the doctor is trying to isolate the causative agent, which is likely to be Pertussis bacillus. Summary of other choices: B: Pfeiffer's bacillus (Haemophilus influenzae): Unlikely as symptoms do not match. C: Listeria: Unlikely as it typically causes foodborne illness, not respiratory infections. D: Klebsiella: Unlikely as it is more commonly associated with pneumonia in immunocompromised individuals.

Correct Answer: A

Rationale: Rationale: 1. Endo agar inhibits the growth of Gram-positive bacteria. 2. Colorless colonies on Endo agar indicate lactose non-fermenting bacteria. 3. Shigella dysenteriae is a lactose non-fermenting, Gram-negative rod, causing dysentery. 4. Salmonella typhi, Escherichia coli, and Proteus vulgaris are lactose fermenters, so they would produce pink colonies on Endo agar. Therefore, the most likely causative agent is Shigella dysenteriae.

Correct Answer: B

Rationale: The correct answer is B: Streptococcus mutans. This bacterium is associated with the formation of dental caries due to its ability to metabolize sugars and produce acids that demineralize tooth enamel. Streptococcus pneumoniae (choice A) is not typically associated with dental caries. Bacillus anthracis (choice C) causes anthrax, not dental caries. Clostridium botulinum (choice D) causes botulism, not dental caries. Streptococcus mutans' unique characteristics make it the correct choice for the bacteria associated with dental caries.

Correct Answer: B

Rationale: I apologize for the confusion, but the correct answer to the question is actually A: microtubules. Microtubules are indeed shaped like hollow cylinders made out of tubulin proteins. They play a crucial role in cell structure, cell division, and intracellular transport. Microfilaments (choice B) are composed of actin proteins and are not shaped like hollow cylinders. Intermediate filaments (choice C) are more rope-like in structure and are made up of various proteins. Flagella (choice D) are whip-like structures used for cell movement and are not shaped like hollow cylinders.

Correct Answer: A

Rationale: The correct answer is A because spores are heat-resistant and require high temperatures for destruction. Autoclaving at 121°C for 15-20 minutes ensures spore destruction due to the high pressure and temperature. Choice B (heating to 80°C) is insufficient to destroy spores. Choice C (boiling at 100°C for 10 minutes) is also inadequate as spores require higher temperatures for elimination. Choice D (None of them) is incorrect as autoclaving is the standard method for spore sterilization.

Correct Answer: A

Rationale: The correct answer is A: Clostridium tetani. Clostridium tetani is responsible for causing tetanus by producing a neurotoxin called tetanospasmin. This neurotoxin blocks inhibitory signals in the central nervous system, leading to muscle spasms and stiffness characteristic of tetanus. Clostridium perfringens (B) causes gas gangrene, Streptococcus pyogenes (C) causes strep throat, and Escherichia coli (D) can cause gastrointestinal infections but not tetanus. Therefore, based on the specific pathogen and its mechanism of action, Clostridium tetani is the correct answer.

Correct Answer: A

Rationale: The correct answer is A: Salk and Sabin vaccines are vaccines against polio. Both Salk and Sabin vaccines are indeed vaccines specifically developed to prevent polio. The Salk vaccine is an inactivated polio vaccine, while the Sabin vaccine is an oral live attenuated vaccine. Therefore, choice B is incorrect as the Sabin vaccine is live attenuated, not inactivated. Choice C is also incorrect because the Salk vaccine is inactivated, not live attenuated. Choice D is incorrect because not all statements are true; only statement A is accurate.

Correct Answer: C

Rationale: The correct answer is C: Clostridium perfringens. This bacterium is the causative agent of gas gangrene due to its ability to produce gas and toxins in anaerobic conditions. Clostridium tetani causes tetanus, Clostridium botulinum causes botulism, and Bacillus anthracis causes anthrax, not gas gangrene. Clostridium perfringens stands out as the correct choice based on its specific association with gas gangrene and its pathogenic mechanisms.

Correct Answer: B

Rationale: The correct answer is B: Cholera. Cholera is caused by Gram-negative curved rod-like bacteria called Vibrio cholerae, commonly found in contaminated water or food. The characteristic symptom of cholera is profuse watery diarrhea, which matches the patient's presentation. Typhoid fever (A) is caused by Salmonella typhi, which is not a curved rod-like bacteria. Diphtheria (C) is caused by Corynebacterium diphtheriae, a Gram-positive bacterium, and does not typically cause diarrhea. Intestinal form of plague (D) is caused by Yersinia pestis, which is not a curved rod-like bacteria and does not typically present with diarrhea.