A patient suffers from severe postoperative pseudomonadous infection. What of the following antibiotics should be administered in this case?

Correct Answer: A

Rationale: The correct answer is A: Amikacin sulfate. Pseudomonas aeruginosa is commonly resistant to many antibiotics, but aminoglycosides like Amikacin have good activity against it. Step 1: Identify the pathogen causing the infection. Step 2: Consider the antibiotic's spectrum of activity against the pathogen. Step 3: Choose an antibiotic with proven efficacy. Amikacin is a good choice due to its effectiveness against Pseudomonas. Choice B, Benzylpenicillin, is a penicillin which is not effective against Pseudomonas. Choice C, Cephazolin, is a cephalosporin with limited activity against Pseudomonas. Choice D, Erythromycin, is a macrolide which is not effective against Pseudomonas.

Correct Answer: D

Rationale: The correct answer is D (All of the above) because all three bacteria listed produce exotoxins that cause severe gastrointestinal illness. Clostridium botulinum produces botulinum toxin causing botulism. Vibrio cholerae produces cholera toxin leading to cholera. Escherichia coli can produce various exotoxins causing different types of severe gastrointestinal illnesses like E. coli O157:H7 causing bloody diarrhea. Therefore, all choices A, B, and C are correct in this case as they all produce exotoxins causing severe gastrointestinal illness.

Correct Answer: A

Rationale: The correct answer is A: Pseudomonas aeruginosa. P. aeruginosa is a Gram-negative rod that is oxidase-positive and lactose non-fermenting. The positive oxidase test indicates the presence of cytochrome c oxidase, a characteristic of P. aerugin. E. coli is lactose fermenting. Salmonella and Shigella are also Gram-negative rods, but they are lactose fermenters, unlike the lactose non-fermenting P. aeruginosa.

Correct Answer: A

Rationale: The correct answer is A: Head lice. Epidemic typhus is transmitted by the body louse, Pediculus humanus humanus, which is different from the head louse, Pediculus humanus capitis. Head lice are not known to transmit epidemic typhus. Body lice are the primary vectors for transmitting epidemic typhus. Fleas are vectors for other diseases such as plague, not epidemic typhus. Ticks are vectors for various diseases but not for epidemic typhus. Therefore, the correct vector for epidemic typhus transmission is body lice, making choice A the correct answer.

Correct Answer: B

Rationale: The correct answer is B: Chlamydia trachomatis. This is because Chlamydia trachomatis is an obligate intracellular bacterium that cannot be cultured on standard agar plates. The symptoms described by the patient, such as pain, burning at urination, and scarce secretion in the morning, are indicative of a possible chlamydial infection. Additionally, the fact that the urine cultures are sterile after 24 hours of incubation suggests that the causative agent is not a typical bacteria like Escherichia coli, Streptococcus pneumoniae, or Neisseria gonorrhoeae, which would normally grow on agar plates. Therefore, Chlamydia trachomatis is the most probable cause of this disease. Summary: A: Escherichia coli - Incorrect, as it is a common cause of urinary tract infections and would typically grow on agar plates. C: Streptococcus pneumoniae - Incorrect, as it is

Correct Answer: A

Rationale: The correct answer is A: protozoans. Pinworms are commonly referred to as Enterobius vermicularis, which are parasitic worms belonging to the phylum Nematoda. Protozoans are single-celled organisms, and pinworms are multicellular worms. Algae are photosynthetic organisms, helminths are parasitic worms (which pinworms fall under), and fungi are eukaryotic organisms that include molds and yeasts. Therefore, protozoans are the correct choice for organisms commonly referred to as pinworms.

Correct Answer: D

Rationale: The correct answer is D, "All of these." Monotrichous bacteria have a single flagellum at one end, amphitrichous have flagella at both ends, and peritrichous have flagella distributed all over the surface. The answer D is correct because it includes all these possibilities based on flagella location. Monotrichous is incorrect as it only refers to a single flagellum, amphitrichous is incorrect as it only refers to flagella at both ends, and peritrichous is incorrect as it only refers to flagella all over the surface. Therefore, the correct answer encompasses all these options.

Correct Answer: A

Rationale: The correct answer is A: Neisseria meningitidis. This is because Neisseria meningitidis is a Gram-negative diplococcus known to cause bacterial meningitis, presenting with fever, headache, and neck stiffness. It is a common cause of meningitis in young adults and teenagers. Streptococcus pneumoniae (B) is a Gram-positive bacteria and a common cause of bacterial pneumonia, not meningitis. Haemophilus influenzae (C) is a Gram-negative coccobacillus that can cause meningitis, but it is less common in adults. Klebsiella pneumoniae (D) is a Gram-negative bacillus known to cause pneumonia and urinary tract infections, not meningitis.

Correct Answer: B

Rationale: Step-by-step rationale for why choice B (Tuberculin is introduced) is correct: 1. Tuberculin test helps identify individuals with latent TB infection. 2. Negative skin-allergic samples suggest absence of active TB. 3. Introducing tuberculin can help confirm latent TB infection. 4. Antibiotics are not prescribed for negative skin-allergic samples. 5. Vaccines are not administered for TB diagnosis. Summary: - Choice A is incorrect as antibiotics are not prescribed for negative skin-allergic samples. - Choice C is incorrect as vaccines are not used for TB diagnosis. - Choice D is incorrect as introducing tuberculin is the appropriate step in this scenario.