The ability of Clostridium tetani to produce exotoxins is encoded by?

Correct Answer: C

Rationale: The correct answer is C: genes with plasmid location. Clostridium tetani produces exotoxins through genes located on plasmids. Plasmids are extrachromosomal genetic elements that carry additional genes. These genes encode for the production of exotoxins in Clostridium tetani. Choices A, B, and D are incorrect because Clostridium tetani does produce exotoxins, it does not have only endotoxin activity, and the genes responsible for exotoxin production are located on plasmids, not solely on the chromosome or both chromosome and plasmid.

Correct Answer: A

Rationale: The correct answer is A: Escherichia coli. E. coli typically produces red colonies on Endo agar due to its ability to ferment lactose. This results in the production of acid, causing the colonies to appear red. Salmonella and Shigella are non-lactose fermenters, so they would appear colorless or transparent on Endo agar. Proteus vulgaris is not commonly associated with red colonies on Endo agar. Therefore, based on the characteristic lactose fermentation pattern, E. coli is the most likely microorganism in this scenario.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pyogenes. This is because Streptococcus pyogenes is a Gram-positive cocci in chains bacterium that is catalase-negative, making it the most likely causative agent in this scenario. Streptococcus pyogenes is a common pathogen causing bacterial endocarditis. Summary of other choices: B: Staphylococcus aureus is a Gram-positive cocci bacterium but is catalase-positive, so it is unlikely in this case. C: Enterococcus faecalis is a Gram-positive cocci bacterium, but it is catalase-negative, which is not consistent with the given information. D: Micrococcus luteus is a Gram-positive cocci bacterium but is catalase-positive, making it an unlikely causative agent.

Correct Answer: A

Rationale: The correct answer is A: Trichomonas vaginalis. Trichomonas vaginalis is a flagellated protozoa that causes the sexually transmitted infection trichomoniasis. The presence of an undulating membrane in vaginal discharge samples is characteristic of Trichomonas vaginalis. Giardia lamblia causes gastrointestinal illness, not vaginal infections. Trypanosoma brucei causes African sleeping sickness transmitted by tsetse flies. Leishmania donovani causes visceral leishmaniasis transmitted by sandflies.

Correct Answer: C

Rationale: The correct answer is C: Gram-negative bacterial outer membrane. Lipopolysaccharides (LPS) are major components of the outer membrane of Gram-negative bacteria. LPS consist of lipid A, core oligosaccharide, and O-antigen. They play a crucial role in the structural integrity and protection of Gram-negative bacteria. Choice A (Gram-positive bacteria) is incorrect because LPS are not present in Gram-positive bacteria. Choice B (Fungal cell walls) is incorrect as LPS are specific to bacterial outer membranes. Choice D (Viral capsids) is incorrect as LPS are not associated with viral structures.