From urine of a 14-year-old boy with the exacerbation of secondary obstructive pyelonephritis Pseudomonas aeruginosa was isolated with a titer of 1000000 microbes per 1 ml. Which antibiotic is most advisable to be administered in this case?

Correct Answer: A

Rationale: The correct answer is A: Ciprofloxacin. Pseudomonas aeruginosa is commonly resistant to Ampicillin, Cefazolinum, and Azithromycin. Ciprofloxacin is a fluoroquinolone antibiotic known for its efficacy against Pseudomonas aeruginosa. Its broad spectrum and ability to penetrate tissues make it the most advisable choice for treating secondary obstructive pyelonephritis caused by this pathogen.

Correct Answer: B

Rationale: The correct answer is B: Tuberculosis and mycobacterioses. Mycobacterium tuberculosis, the causative agent of tuberculosis, and other mycobacteria can survive in the soil for extended periods. Here's the rationale: 1. Mycobacteria have a waxy cell wall that provides resistance to harsh environmental conditions. 2. The slow growth rate of mycobacteria allows them to persist in the soil for long periods. 3. Tuberculosis and mycobacterioses are known to be transmitted through environmental exposure, including soil. 4. Colibacillosis and cholera (Choice C) are caused by enteric bacteria that do not survive well in soil. 5. Leptospirosis and plague (Choice D) are bacterial diseases transmitted through animal hosts and are not known to be soil-borne.

Correct Answer: D

Rationale: Step-by-step rationale for why answer D is correct: 1. Tetanus exotoxins are produced by Clostridium tetani bacteria. 2. Once formed, the exotoxins can spread through the bloodstream. 3. Retrograde axonal transport allows the exotoxins to travel to the central nervous system (CNS). 4. In the CNS, the exotoxins can cause the symptoms of tetanus. 5. Options A, B, and C are incorrect as tetanus exotoxins do not follow those pathways. In summary, option D is correct as tetanus exotoxins can spread through the blood and reach the CNS via retrograde axonal transport, while the other options do not align with the known pathophysiology of tetanus.

Correct Answer: D

Rationale: The correct answer is D. Staphylococcus aureus, Escherichia coli, and Clostridium difficile are all known for causing hospital-acquired infections. Staphylococcus aureus can cause skin infections and pneumonia. Escherichia coli can lead to urinary tract infections. Clostridium difficile is associated with gastrointestinal infections. Each of these bacteria has been linked to healthcare-associated infections due to their ability to spread in healthcare settings. Therefore, the correct answer is D. Choices A, B, and C are incorrect because each of these bacteria individually is known to cause hospital-acquired infections.

Correct Answer: B

Rationale: The correct answer is B: Typhoid fever, Brucellosis. Both Typhoid fever and Brucellosis are bacterial infections that can lead to bacteremia, the presence of bacteria in the bloodstream. In Typhoid fever, the causative agent Salmonella typhi can enter the bloodstream, causing bacteremia. Similarly, Brucellosis, caused by Brucella species, can also result in bacteremia. Choice A is incorrect because bacteremia is not typically observed in Diphtheria. Choice C, Cholera, is caused by a toxin-producing bacterium and does not usually lead to bacteremia. Choice D, Dysentery, is a condition characterized by bloody diarrhea and is primarily caused by parasites or bacteria that typically do not lead to bacteremia.

Correct Answer: C

Rationale: The correct answer is C: Measles serological test. This is because the clinical presentation of high fever, maculopapular rash, and Filatov-Koplik's spots on the buccal mucosa are classic symptoms of measles. The presence of Filatov-Koplik's spots is highly specific for measles. Performing a measles serological test will help confirm the diagnosis by detecting measles-specific antibodies in the blood. Incorrect choices: A: Mumps serological test - Mumps typically presents with parotitis (swelling of the parotid glands) and not with Filatov-Koplik's spots. B: Enteroviruses serological test - Enteroviruses do not typically cause Filatov-Koplik's spots or the classic triad of symptoms seen in measles. D: Influenza virus serological test - Influenza virus does not cause Filatov-Koplik's spots and the characteristic rash seen

Correct Answer: C

Rationale: The correct answer is C (60 years) because as individuals age, their immune system weakens, making them more susceptible to infectious diseases. Around the age of 60, people are more likely to succumb to infections, leading to a higher mortality rate. Choices A, B, and D are incorrect because they are younger ages, and the likelihood of infectious diseases causing a significant proportion of deaths increases with age.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. The presence of Gram-positive cocci in pairs indicates a bacterial morphology consistent with Streptococcus pneumoniae, a common cause of pneumonia. This bacterium is known to appear in pairs or short chains on Gram stain. Staphylococcus aureus (B) typically presents as clusters of Gram-positive cocci, Neisseria meningitidis (C) is a Gram-negative diplococcus, and Klebsiella pneumoniae (D) is a Gram-negative rod, making them less likely causative agents in this scenario.

Correct Answer: C

Rationale: The correct answer is C: Thick peptidoglycan layer. Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet stain in the Gram staining process, leading to a purple color. This thick layer is a defining characteristic of Gram-positive bacteria. Rationale: A: Thin peptidoglycan layer is incorrect because Gram-positive bacteria have a thick peptidoglycan layer. B: Presence of an outer membrane is incorrect because Gram-positive bacteria lack an outer membrane. D: Presence of lipopolysaccharides is incorrect because lipopolysaccharides are typically found in the outer membrane of Gram-negative bacteria, not Gram-positive bacteria.