This expert group investigated the potential role of nonpathogenic microorganisms in VAP. Three hundred sixty-nine VAP patients were identified during the study period. Only 29 episodes were considered to have been caused by commensal pathogens. The percentage of pathogens of unknown etiology was not reported. Polymicrobial VAP was found in 77 patients, and these patients were excluded from the study. Most patients had risk factors for more virulent or resistant pathogens like COPD, glucocorticoid therapy, or immunosuppression. Although the onset of 10 cases occurred before the sixth ICU day, all Gram-negative commensal pathogens that were isolated were sensitive to therapy with a third-generation cephalosporin or amoxicillin/clavulanic acid. Seven of 29 patients did not receive adequate treatment, and mortality did not increase significantly. Although the authors attribute a pathogenic role to commensal bacteria, they did not find any difference in mortality rate between patients with or without VAP. In addition, besides the limited relevance to mortality, only 20% of patients who died had received histologic confirmation of a diagnosis of pneumonia. Commensal pathogens can produce fulminant infections in immunocompromised patients, but this is the first study that has suggested the need to treat commensal isolates in patients with VAP. Future investigations are needed to define the pathogenic role of commensal agents in these kinds of patients.
The occurrence of and effect on prognosis of delays in the beginning of the treatment of VAP have not been reported before, to our knowledge. Appropriate initial antibiotic treatment has been reported to reduce in-hospital mortality. Iregui et al have found an increase in the hospital mortality rate with delayed initial treatment. Adequate initial treatment usually has been defined as an antibiotic with in vitro susceptibility to the pathogen isolated in respiratory samples. This definition needs the addition of onset timing in antibiotic administration. The most common cause of inadequate initial treatment was a delay in writing the medical orders. The presence of a resistant organism accounted for < 20% of cases. It is important to note that diagnostic delays were not counted, although radiologic criteria included an infiltrate persistence of > 72 h. Inadequate clinical evaluation and waiting for microbiological results were reasons of delayed empiric treatments.