The present invention is synergistic antibiotic compositions having pH adjusted profiles for manufacturing combination, and administration, particularly for patients at risk or suffering from ventilator-associated pneumonia (VAP) and ventilator associated tracheal (VAT) bronchitis. Antibiotic compositions containing fosfomycin and aminoglycosides having individually predetermined and selected pH ranges are manufactured and stored for in combination prior to aerosolization, preferably with a specially designed in-line nebulizer attached to a ventilator.
