When a smear is stained by Burri-Gins method a mucous structure that is tightly bound with the cellular wall of bacteria and has well-defined outer boundaries can be detected. This element of a bacteria cell is called:

Correct Answer: A

Rationale: The correct answer is A: Capsule. A capsule is a mucous structure tightly bound to the bacterial cell wall with distinct outer boundaries. This structure helps bacteria evade the host immune system, resist desiccation, and adhere to surfaces. In contrast, spores are resistant structures formed by certain bacteria for survival, filaments are long chains of bacterial cells, and ribosomes are cellular organelles responsible for protein synthesis. Therefore, based on the characteristics described in the question, the most appropriate choice is A: Capsule.

Correct Answer: A

Rationale: The correct answer is A: They are enveloped viruses. Rhabdoviridae family consists of enveloped viruses, which means they have a lipid envelope surrounding their protein coat. This envelope helps the virus in infecting host cells and evading the immune system. The other choices are incorrect because B: They cause plague is not true as Rhabdoviridae family typically causes diseases like rabies in mammals. C: They have spherical shape is incorrect as rhabdoviruses have a bullet-shaped structure. D: They infect only humans is also incorrect as Rhabdoviridae viruses can infect a wide range of hosts beyond just humans.

Correct Answer: B

Rationale: The correct answer is B: EIEC. This strain of E. coli can cause bloody diarrhea in children similar to shigellosis due to its ability to invade and replicate within the intestinal epithelial cells, leading to inflammation and bloody stools. ETEC (A) causes watery diarrhea due to enterotoxins. EAEC (C) causes persistent diarrhea. EPEC (D) causes attaching and effacing lesions on the intestinal mucosa without invasion.

Correct Answer: A

Rationale: The correct answer is A: Trichomonas vaginalis. Trichomonas vaginalis is a sexually transmitted protozoan parasite that causes trichomoniasis, characterized by foamy purulent vaginal discharges. Microscopy of vaginal discharge showing flagellated protozoa with an undulating membrane and pear-shaped structure is indicative of Trichomonas vaginalis. Trypanosoma gambiense causes African sleeping sickness and is transmitted by tsetse flies. Leishmania donovani causes visceral leishmaniasis transmitted by sandflies. Lamblia intestinalis causes giardiasis and is characterized by diarrhea and flatulence.

Correct Answer: D

Rationale: The correct answer is D: Helicobacter pylori. Helicobacter pylori is a known bacterium associated with causing duodenal ulcers. The presence of Gram-negative curved bacteria in the biopsy along with a highly positive rapid urease test is characteristic of H. pylori infection. Vibrio cholerae causes cholera, not duodenal ulcers. Campylobacter fetus is associated with gastroenteritis, not duodenal ulcers. Acinetobacter baumannii is a nosocomial pathogen, not typically associated with duodenal ulcers. In summary, the unique combination of findings in this case points towards H. pylori as the most likely cause of the disease.

Correct Answer: B

Rationale: The correct answer is B: Helicobacter pylori. This bacterium is responsible for stomach acid formation by producing an enzyme called urease, which converts urea into ammonia and carbon dioxide, leading to an increase in stomach pH. Staphylococcus aureus (A) does not cause stomach acid formation. Bacillus cereus (C) and Clostridium botulinum (D) are not involved in stomach acid processes.

Correct Answer: C

Rationale: Rationale: Choice C is correct because immunomodulators can indeed be natural (e.g., cytokines) or artificial compounds (e.g., synthetic peptides). They work by modulating the immune response, enhancing or suppressing it as needed. Choice A is incorrect because immunomodulators can stimulate both humoral and cellular immune responses. Choice B is incorrect as isoniazid is primarily an antibiotic used to treat tuberculosis, not an immunomodulator. Choice D is incorrect because immunomodulators can have varying effects on the immune response, not just suppress it.

Correct Answer: C

Rationale: The correct answer is C: 8. The embryonic phase in humans lasts until the end of week 8. During this time, the major organs and structures of the body begin to form. After week 8, the developing organism is referred to as a fetus. Choice A (2) is too early for this transition to occur, Choice B (6) is also premature, and Choice D (12) is too late as the embryonic phase ends before week 12. Therefore, the correct answer is C (8) as it accurately reflects the timeline of embryonic development in humans.

Correct Answer: D

Rationale: The correct answer is D because fires from flammable metals require specialized Class D fire extinguishers designed to extinguish these unique types of fires. Class A, B, and C fire extinguishers are not suitable for flammable metal fires as they are designed for different types of materials and fire classes. Class A extinguishers are for ordinary combustibles, Class B for flammable liquids, and Class C for electrical fires. Therefore, Class D fire extinguishers are specifically designed for flammable metal fires, making them the correct choice for this scenario.