Correct Answer: C

Rationale: Neonatal meningitis is commonly caused by E. coli K1 and group B streptococci due to their ability to cross the blood-brain barrier in newborns. E. coli K1 is a frequent cause in early-onset cases, while group B streptococci are common in late-onset cases. Neisseria meningitidis and streptococcus agalactiae are not as likely to cause neonatal meningitis. Listeria and shigella are also uncommon causes in neonates. Therefore, choice C is the most likely pair of organisms responsible for neonatal meningitis.

Correct Answer: A

Rationale: The correct answer is A: Sabouraud. Sabouraud agar is specifically designed to promote the growth of fungi due to its low pH and high glucose content. The cream-like colonies indicate fungal growth, as fungi often appear as fluffy or powdery colonies on Sabouraud agar. Lowenstein-Jensen is used for mycobacteria, Roux for diphtheria, and Loeffler for Corynebacterium diphtheriae. Therefore, Sabouraud is the most suitable medium for detecting fungal contamination based on the characteristics of the colonies formed.

Correct Answer: B

Rationale: The correct answer is B: Conjugation. Conjugation involves the transfer of genetic material from a donor cell to a recipient cell through direct cell-to-cell contact, typically mediated by a conjugative plasmid. During conjugation, a conjugative pilus forms a bridge between the donor and recipient cells, allowing the transfer of genetic material. A: Replication is the process of copying DNA to produce two identical DNA molecules. It does not involve the transfer of genetic material between cells. C: Transformation is the uptake and incorporation of foreign DNA from the environment by a bacterial cell. It does not require direct cell-to-cell contact. D: Transduction is the transfer of genetic material from one bacterium to another by a bacteriophage vector. It does not involve direct cell-to-cell contact between the donor and recipient cells.

Correct Answer: A

Rationale: The correct answer is A: Vibrio cholerae. 1. Vibrio cholerae is a Gram-negative, comma-shaped bacterium known to cause cholera. 2. Shigella dysenteriae causes dysentery, not cholera. 3. Salmonella typhi causes typhoid fever, not cholera. 4. Campylobacter jejuni causes gastroenteritis, not cholera. Therefore, based on the symptoms presented and the characteristics of the bacterium, Vibrio cholerae is the most likely microorganism.

Correct Answer: A

Rationale: The correct answer is A: Plague. The presence of ovoid Gram-negative bipolar-stained bacilli with a delicate capsule in the sputum is characteristic of Yersinia pestis, the causative agent of plague. Plague presents with symptoms like fever, chills, and cough. Plague is a zoonotic disease usually transmitted through fleas from rodents. The other choices (B: Tuberculosis, C: Leptospirosis, D: Brucellosis) can be ruled out based on the specific description of the bacteria in the sputum. Tuberculosis is caused by Mycobacterium tuberculosis, which is not Gram-negative. Leptospirosis is caused by Leptospira, which are spirochetes and not ovoid bacilli. Brucellosis is caused by Brucella species, which are small, coccobacilli and not ovoid bacilli.