Which bacteria produce exotoxins that affect the nervous system?

Correct Answer: A

Rationale: The correct answer is A: Clostridium botulinum and Clostridium tetani. Both bacteria produce exotoxins that affect the nervous system. Clostridium botulinum produces botulinum toxin, causing botulism, leading to muscle paralysis. Clostridium tetani produces tetanospasmin, causing tetanus, leading to muscle stiffness and spasms. Choice B (Escherichia coli and Salmonella) are known for causing gastrointestinal infections, not specifically affecting the nervous system. Choice C (Bacillus anthracis and Listeria monocytogenes) produce toxins that primarily affect other body systems, not the nervous system. Choice D (Pseudomonas aeruginosa and Staphylococcus aureus) are associated with skin and respiratory infections, not neurological effects.

Correct Answer: A

Rationale: The correct answer is A: Erythrocytic schizogony. In this case, the patient most likely has malaria, specifically caused by Plasmodium falciparum. The fever attacks every 2 days (tertian fever) are characteristic of P. falciparum infection. The cycle of erythrocytic schizogony in P. falciparum is around 48 hours, leading to the recurring fever pattern. Choices B, C, and D are incorrect as tissue schizogony does not cause the characteristic fever pattern, exotoxins are not typically involved in malaria fever, and gametocytes do not directly cause fever attacks.

Correct Answer: B

Rationale: The correct answer is B: Sugar meat pepton broth, sugar meat pepton agar. These nutrient media are optimal for Corynebacterium diphtheriae cultivation due to their ability to support the growth of this bacterium. Sugar meat pepton broth provides a liquid medium with essential nutrients, while sugar meat pepton agar provides a solid surface for bacterial growth and isolation. Incorrect choices: A: Diphtheriae does not require specific conditions for cultivation. C: Salt egg yolk agar is not commonly used for Corynebacterium diphtheriae. D: Endomedium and Ploskirev medium are not standard media for diphtheria testing.

Correct Answer: B

Rationale: The correct answer is B: Thayer-Martin agar. This selective media contains antibiotics that inhibit the growth of other organisms while allowing Neisseria gonorrhoeae to grow. The antibiotics in Thayer-Martin agar include vancomycin, colistin, nystatin, and trimethoprim, which target different types of bacteria, ensuring the isolation of N. gonorrhoeae. Phenylethyl alcohol agar (A) is used to isolate gram-positive organisms, not N. gonorrhoeae. MacConkey agar (C) is selective for gram-negative enteric bacteria. Mannitol salt agar (D) is used for isolating Staphylococcus species based on their ability to ferment mannitol.

Correct Answer: C

Rationale: The correct hierarchical order for virus classification is order, family, subfamily, genus, species. This is because classification starts at a broader level (order) and narrows down to a more specific level (species). Order comes first to group viruses based on common characteristics, followed by family, which further categorizes them. Subfamily refines the classification, then genus groups similar viruses together, and species distinguishes different strains within a genus. Choice A is incorrect because it places genus before family, which is not the correct sequence. Choice B is incorrect as it starts with species, which is the most specific level. Choice D is incorrect because it places genus at the beginning, which is too specific for the hierarchical order.

Correct Answer: B

Rationale: The correct answer is B: Pseudomonas aeruginosa. This bacterium is known for producing biofilms on medical devices due to its ability to adhere and form a slimy layer that protects it from antibiotics and the host immune system. Pseudomonas aeruginosa is commonly associated with healthcare-associated infections. Clostridium tetani (A) causes tetanus, not known for biofilm production on medical devices. Salmonella enterica (C) causes foodborne illnesses, not typically associated with medical device biofilms. Staphylococcus aureus (D) is a common pathogen in healthcare settings but is not specifically known for biofilm production on medical devices.

Correct Answer: B

Rationale: The correct answer is B: Flagella. Flagella are whip-like appendages used by bacteria for movement. They rotate in a corkscrew motion to propel the bacteria through their environment. Pili (choice A) are hair-like structures used for attachment, not movement. Capsules (choice C) are protective layers around bacteria, not involved in movement. Fimbriae (choice D) are also used for attachment and biofilm formation, not for movement. Therefore, the correct choice is B as flagella are specifically adapted for bacterial motility.

Correct Answer: C

Rationale: Rationale for choice C (Strep. pneumoniae): 1. Strep. pneumoniae is a common cause of bacterial meningitis. 2. It is a leading pathogen responsible for meningitis in adults and children. 3. It can invade the bloodstream and reach the meninges, causing inflammation. 4. Treatment guidelines often include antibiotics effective against Strep. pneumoniae. Summary of why other choices are incorrect: A. Staph. aureus is not a common cause of meningitis. B. Strep. pyogenes typically causes streptococcal infections but not meningitis. D. "None of the above" is incorrect as Strep. pneumoniae can cause meningitis.

Correct Answer: A

Rationale: Rationale: 1. Unicellular organisms with two layers in cytoplasm = Entamoeba gingivalis. 2. Wide pseudopodia = characteristic of Entamoeba genus. 3. Entamoeba histolytica causes amoebic dysentery, not dental plaque. 4. Trichomonas tenax causes periodontal disease, not dental plaque. 5. Lamblia intestinalis causes giardiasis, not related to dental plaque.