recent hospitalization (last 90 days), residence in a nursing home, treatment in a hemodialysis clinic, and prior antibiotic use (last 90 days). possible empirical therapy combinations include (but are not limited to): vancomycin/linezolid and ciprofloxacin, cefepime and gentamicin/amikacin/tobramycin vancomycin/linezolid and ceftazidime ureidopenicillin plus β-lactamase inhibitor such as piperacillin/tazobactam or ticarcillin/clavulanate a carbapenem (e.g., imipenem or meropenem) therapy is typically changed once the causative bacteria are known and continued until symptoms resolve (often 7 to 14 days). for patients with vap not caused by nonfermenting gram-negative bacilli (like acinetobacter, pseudomonas aeruginosa) the available evidence seems to support the use of short-course antimicrobial treatments (< or =10 days). people who do not have risk factors for mdr organisms may be treated differently depending on local knowledge of prevalent bacteria. appropriate antibiotics may include ceftriaxone, ciprofloxacin, levofloxacin, or ampicillin/sulbactam. as of 2005, there is ongoing research into inhaled antibiotics as an adjunct to conventional therapy. tobramycin and polymyxin b are commonly used in certain centres but there is no clinical evidence to support their use. prognosis vap occurring early after intubation typically involves fewer resistant organisms and is thus associated with a more favorable outcome. because respiratory failure requiring mechanical ventilation is itself associated with a high mortality, determination of the exact contribution of vap to mortality has been difficult. as of 2006, estimates range from 33% to 50% death in patients who develop vap. mortality is more likely when vap is associated with certain microorganisms (pseudomonas, acinetobacter), blood stream infections, and ineffective initial antibiotics. vap is especially common in people who have acute respiratory distress syndrome (ards). epidemiology between 8 and 28% of patients receiving mechanical ventilation are affected by vap. vap can develop at any time during ventilation, but occurs most often in the first week of mechanical ventilation. there is some evidence for gender differences in the course of vap: men have been found to get vap more often, but women are more likely to die after contracting vap. recent reports indicate that patients with coronavirus disease 2019 who require mechanical ventilation in an intensive care unit are at increased risk of ventilator-associated pneumonia, compared to patients without covid-19 ventilated in the same unit and patients who had viral pneumonitis arising from viruses other than sars-cov-2. why this increased susceptibility should be present remains uncertain, as the noted reports adjusted for duration of ventilation, it is likely that the increased susceptibility relates impaired innate immunity in the lungs. however several observational studies have identified the use of glucocorticoids as a factor associated with increased risk of vap and other hospital-acquired infections.