Potentially resistant microorganisms in intubated patients with hospital-acquired pneumonia: the interaction of ecology, shock and risk factors.

PURPOSE: As per 2005 American Thoracic Society and Infectious Disease Society of America (ATS/IDSA) guidelines for managing hospital-acquired pneumonia, patients with early-onset pneumonia and without risk factors do not need to be treated for potentially resistant microorganisms (PRM).
METHODS: This was a secondary analysis of a prospective, observational, cohort, multicentre study conducted in 27 ICUs from nine European countries.
RESULTS: From a total of 689 patients with nosocomial pneumonia who required mechanical ventilation, 485 patients with confirmed etiology and antibiotic susceptibility were further analysed. Of these patients, 152 (31.3 %) were allocated to group 1 with early-onset pneumonia and no risk factors for PRM acquisition, and 333 (68.7 %) were classified into group 2 with early-onset pneumonia with risk factors for PRM or late-onset pneumonia. Group 2 patients were older and had more chronic renal failure and more severe illness (SAPS II score, 44.6 ± 16.5 vs. 47.4 ± 17.8, p = 0.04) than group 1 patients. Trauma patients were more frequent and surgical patients less frequent in group 1 than in group 2 (p < 0.01). In group 1, 77 patients (50.7 %) had PRM in spite of the absence of classic risk factors recognised by the current guidelines. A logistic regression analysis identified that presence of severe sepsis/septic shock (OR = 3.7, 95 % CI 1.5-8.9) and pneumonia developed in centres with greater than 25 % prevalence of PRM (OR = 11.3, 95 % CI 2.1-59.3) were independently associated with PRM in group 1 patients.
CONCLUSIONS: In patients admitted to ICUs with a prevalence of PRM greater than 25 % or with severe sepsis/septic shock, empiric therapy for group 1 nosocomial pneumonia requiring mechanical ventilation should also include agents likely to be effective for PRM pathogens.