A worker of a cattle farm consulted a surgeon about fever up to 40oC, headache, weakness. Objective examination of his back revealed hyperaemia and a dark red infiltration up to 5 cm in diameter with black bottom in the center and some pustules. What disease are these presentations typical for?

Correct Answer: A

Rationale: The correct answer is A: Anthrax. The symptoms of fever, headache, weakness, and the skin lesion described (hyperemic with a dark red infiltration, black center, and pustules) are characteristic of cutaneous anthrax. The black center is known as an eschar. Anthrax is caused by the bacterium Bacillus anthracis, commonly found in cattle. Plague (choice B) typically presents with swollen lymph nodes (buboes) and is caused by Yersinia pestis. Tularemia (choice C) presents with fever, ulcer at the site of infection, and lymphadenopathy, caused by Francisella tularensis. Furuncle (choice D) is a localized skin infection typically caused by Staphylococcus aureus, presenting as a red, swollen, and painful bump.

Correct Answer: C

Rationale: The correct answer is C: Escherichia coli. E. coli is a gram-negative bacterium, which means it has an outer membrane containing lipopolysaccharides (LPS), also known as endotoxins. Endotoxins are released when the bacterium is destroyed, causing an inflammatory response. Streptococcus pneumoniae (choice A) is a gram-positive bacterium and does not produce endotoxins. Clostridium tetani (choice B) produces exotoxins, not endotoxins. Staphylococcus aureus (choice D) is also a gram-positive bacterium and does not produce endotoxins. In summary, E. coli is the correct answer because it is a gram-negative bacterium that produces endotoxins, while the other choices are gram-positive bacteria that do not produce endotoxins.

Correct Answer: C

Rationale: Rifampicin is the correct answer because it is a first-line antibiotic for treating pulmonary tuberculosis. It has excellent bactericidal activity and penetrates well into lung tissues where the infection is located. Rifampicin is also known for preventing the development of resistance. Tetracycline (A) and Furasolidone (B) are not commonly used for tuberculosis treatment. Bactrim (D) is a combination of sulfamethoxazole and trimethoprim, not effective for tuberculosis treatment.

Correct Answer: A

Rationale: Rationale: The correct answer is Amebiasis (choice A) because the patient's symptoms of acute gastrointestinal disorders and prolonged stay in an African country suggest exposure to Entamoeba histolytica, the causative agent of amebiasis. This protozoal infection commonly occurs in tropical regions, including Africa. Trypanosomosis (choice B) is caused by Trypanosoma species transmitted by tsetse flies, primarily found in sub-Saharan Africa. Leishmaniasis (choice C) is transmitted by sandflies and presents with skin lesions or visceral involvement, not acute gastrointestinal symptoms. Malaria (choice D) is caused by Plasmodium parasites transmitted by mosquitoes and typically presents with fever, not acute gastrointestinal disorders. Therefore, choices B, C, and D are incorrect based on the patient's clinical presentation and travel history.

Correct Answer: D

Rationale: The correct answer is D because all three bacteria (Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae) can cause bacterial meningitis. Neisseria meningitidis is a common cause of meningococcal meningitis, Haemophilus influenzae can cause H. influenzae meningitis, and Streptococcus pneumoniae is a leading cause of pneumococcal meningitis. Therefore, all of the above choices are correct. The other choices are incorrect because each of the bacteria listed can independently cause bacterial meningitis, so none of them alone can be the sole correct answer.

Correct Answer: D

Rationale: The correct answer is D: Fibers at the vertices of the icosahedron. Adenoviruses have fibers at the vertices of the icosahedron, which give them their distinctive pattern. These fibers help in attaching to host cells. Choices A, B, and C are incorrect because adenoviruses do not have a lipid envelope, helical capsid, or ssDNA. Adenoviruses have a non-enveloped icosahedral capsid and contain dsDNA. This makes choice D the correct answer as it specifically relates to the unique structural feature of adenoviruses.

Correct Answer: A

Rationale: The correct answer is A: Picornaviridae. Picornaviruses, such as enteroviruses, are commonly found in the feces of infected individuals. Therefore, their presence in water indicates fecal contamination and the need for additional purification. B: Herpesviridae are not typically associated with fecal contamination. C: Flaviviridae are mainly transmitted through arthropods like mosquitoes, not fecal contamination. D: Retroviridae, including HIV, are not typically excreted in high levels in feces and are not indicators of fecal contamination.

Correct Answer: A

Rationale: Step 1: Giardiasis is caused by Giardia intestinalis, which is a well-known protozoan parasite. Step 2: Protozoans are single-celled eukaryotic organisms commonly found in water sources. Step 3: Giardia intestinalis infects the intestine, causing symptoms like diarrhea and abdominal cramps. Step 4: Bacteria (Choice B) are prokaryotic organisms, different from protozoans. Step 5: Fungi (Choice C) are also eukaryotic but are not responsible for causing Giardiasis. Step 6: Viruses (Choice D) are not cellular and cannot independently cause Giardiasis. In summary, the correct answer is A (protozoan) because Giardia intestinalis is a protozoan parasite specifically known to cause Giardiasis, while the other choices (Bacterium, Fungus, Virus) do not match the characteristics of the

Correct Answer: B

Rationale: The correct answer is B: Carrying antibiotic resistance genes. Bacterial plasmids are small, circular DNA molecules that can carry genes, including those for antibiotic resistance. This allows bacteria to survive exposure to antibiotics. Plasmids do not directly regulate bacterial growth (A), produce toxins (C), or facilitate endospore formation (D). Plasmids play a crucial role in the spread of antibiotic resistance among bacteria.