Which bacteria produce urease enzyme to neutralize stomach acid?

Correct Answer: C

Rationale: Rationale: 1. Helicobacter pylori is known for producing urease enzyme to neutralize stomach acid. 2. Urease enzyme converts urea into ammonia, buffering the acidic pH. 3. This adaptation allows H. pylori to survive in the acidic environment of the stomach. 4. Salmonella typhi, Escherichia coli, and Shigella flexneri do not produce urease. 5. Therefore, C is the correct answer based on the unique urease-producing capability of H. pylori.

Correct Answer: D

Rationale: The correct answer is D: Moeller. Moeller staining method is specifically designed to detect spores due to its ability to differentiate between the spore and the vegetative cell. It involves applying multiple stains such as malachite green, safranin, and heat to visualize the endospore structure. This method is essential for proving the formation of spores as it highlights the resistant spore structures within the bacterial cell. A: Klett and Gins is not used for spore staining. B: Ziehl-Neelsen is used for acid-fast staining, not spore staining. C: Gram and Loeffler's are used for gram staining, not spore staining.

Correct Answer: B

Rationale: The correct answer is B: Agglutination reaction. This test is commonly used to detect specific antibodies or antigens. In this case, it can be used to detect plague antigens in the rat tissues or antibodies in the villagers. This test is rapid, sensitive, and can help establish the presence of the causative agent quickly. A: Ring precipitation reaction is not typically used for diagnosing plague and is more commonly used in other types of infections. C: Passive agglutination reaction is not specific for plague and is more commonly used for detecting specific antibodies in diseases like syphilis. D: Neutralization reaction is not typically used for diagnosing plague and is more commonly used to determine the presence of neutralizing antibodies in viral infections.

Correct Answer: B

Rationale: The correct answer is B: Reverse transcriptase and protease. Reverse transcriptase converts viral RNA into DNA, a crucial step in viral replication. Protease is responsible for cleaving viral polyproteins into functional proteins. Targeting both enzymes disrupts viral replication. Choice A is incorrect as integrase is not a main target in current therapy. Choice C is incorrect because protease is targeted along with reverse transcriptase, not integrase. Choice D is incorrect as targeting viral glycoproteins is not a main strategy in anti-HIV therapy.

Correct Answer: C

Rationale: The correct answer is C because Leptospira cannot be cultivated on blood and chocolate agar. The bacterium requires specialized media such as Ellinghausen-McCullough-Johnson-Harris (EMJH) medium for growth. Blood and chocolate agar do not provide the necessary nutrients for the bacterium's growth. Leptospira is a fastidious organism that has unique culture requirements. Therefore, the statement that Leptospira can be cultivated on blood and chocolate agar is incorrect. The other choices are correct: A - Leptospirosis is an acute infectious disease with a typical geographic distribution, B - Reservoirs of leptospira are different wild and domestic animals, mainly rodents, and D - Doxycycline and penicillins are drugs of choice for the treatment of leptospirosis.

Correct Answer: B

Rationale: Rationale: 1. Enteropathogenic E.coli (EPEC) adheres to the intestinal wall using bundle-forming pili. 2. EPEC produces toxins that disrupt cell structure and function, leading to diarrhea. 3. Shigella spp. invade intestinal cells, Salmonella spp. invade and multiply within cells, and Vibrio cholerae produces cholera toxin causing profuse watery diarrhea. Summary: A, C, and D choices are incorrect because they do not specifically adhere to the intestine wall and produce toxins like EPEC does.

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.

Correct Answer: A

Rationale: The correct answer is A: incidence. Incidence refers to the number of new cases of a disease occurring within a specific time period in relation to the healthy population. It helps in understanding the risk of developing the disease. Prevalence (B) is the total number of existing cases at a given point in time. Virulence (C) is the severity of the disease once contracted. Mortality (D) refers to the number of deaths due to the disease, not the new cases. Therefore, the correct term for new cases is incidence.

Correct Answer: A

Rationale: 1. Bordetella pertussis causes whooping cough. 2. It secretes toxins that damage the respiratory tract. 3. Symptoms include severe coughing fits and the characteristic "whoop" sound. 4. Clostridium tetani causes tetanus, not whooping cough. 5. Haemophilus influenzae causes various infections, not whooping cough. 6. Staphylococcus aureus causes skin infections, not whooping cough.