Role of bacteriological investigation of endotracheal aspirate in diagnosis of ventilator-associated pneumonia

Ventilator associated pneumonia (VAP) is a common complication of ventilatory support for patients with acute respiratory failure, currently related to high mortality rate. Therefore, this complication of mechanical ventilation requires a prompt diagnosis and adequate antibiotic treatment. The study aimed to investigate the role of endotracheal aspirate (ETA) surveillance cultures in identifying the aetiology of VAP earlier. The study was conducted over a period of 12 months and included 152 patients under mechanical ventilation for >48 h from different ICUs of Assiut University Hospitals. Quantitative cultures of ETA at threshold of 105cfu/ml were performed. The organisms were primarily identified by colony morphology, microscopy of Gram stain and standard biochemical tests. The antibiotic resistance pattern of the isolated bacteria was determined by Kirby-Bauer disk diffusion method. VAP was suspected in 92/152 patients (60.53%). Microbiological support for VAP was obtained by ETA in 90 patients. Positive cultures occurred in 88 patients, the infection was polymicrobial in 50 (54.34%) of cultures. Major isolated pathogenic bacteria were gram negative (54.79%); Klebsiella species was the commonest organism (23.29 %). Gram positive bacteria were detected in 42.47% of the cultures; methicillin resistant Staphylococcus aureus (MRSA) was the predominant organism (24.40%). Gram negative bacteria showed high resistance to penicillins, cephalosporins and quinolones, the least resistance was to imipenem. Mortality was higher in VAP group (47.8%) than non VAP (30%). It is indicated that quantitative cultures of ETA is a useful method for early diagnosis of VAP with subsequent proper selection of adequate therapy.