Final answer:
The choice of antibiotics for an infant with late-onset pneumonia on mechanical ventilation should cover a broad range of pathogens, with ampicillin and gentamicin or vancomycin and cefotaxime being possible options. The final decision should be guided by local resistance patterns and the specifics of the patient's condition.
Step-by-step explanation:
The appropriate antimicrobial agents to treat an infant diagnosed with late-onset pneumonia and receiving invasive mechanical ventilatory support would depend on the causative pathogen and the local resistance patterns. Given the limited information, the choice of antibiotics should cover a wide range of possible pathogens, including those resistant to commonly used antibiotics. In cases of antibiotic resistance concerns, especially with the emergence of drug-resistant strains of Streptococcus pneumoniae, broad-spectrum antibiotics such as cefotaxime or other ß-lactam antibiotics might be appropriate. For neonatal meningitis, treatment with ß-lactam antibiotics such as ampicillin plus gentamicin is a standard approach.
Therefore, the treatment option for the scenario provided might be ampicillin and gentamicin or vancomycin and cefotaxime, depending on local antibiotic resistance patterns and the specifics of the patient's condition. However, without further details such as cultures and sensitivity data, a precise antibiotic regimen cannot be determined. Empirical therapy should be adjusted based on the culture results and the sensitivity patterns of the pathogen involved.