Impact of microbial ecology on accuracy of surveillance cultures to predict multidrug resistant microorganisms causing ventilator-associated pneumonia

•By moving to a new hospital we detected a change in our local epidemiology.•We assessed SC accuracy to predict VAP etiology in different microbial ecology settings.•We checked SC effectiveness whatever was the rate of MDRM.•SC capacity to increase the rate of appropriate treatment was only present with a high rate of MDRM.

SummaryObjectivesThe objective of this study was to assess surveillance cultures (SC) prediction accuracy in two periods and settings of the same Department with a different microbiological epidemiology (high and low prevalence of multi-drug resistant microorganisms (MDRM)).MethodsProspective and observational study. SC were obtained twice a week in consecutive mechanically ventilated patients. Patients fulfilling VAP criteria were analyzed.Results440 patients were followed up, 71 patients had VAP (50 in period I and 21 in period II). MDRM causing VAP were more prevalent in the first period (48% vs. 19%; p = 0.033). The rate of empirical appropriate treatment in period I was lower than in period II (52% vs.76%; p = 0.031). SC prediction accuracy was similar in the two periods (80% vs. 81%; p = 0.744). However, if antibiotic treatment had been guided by SC, the percentage of appropriate treatment would have increased by 28% in the first period but only by 5% in the second; p = 0.024.ConclusionsSC were able to predict VAP etiology in 80% of cases regardless the prevalence of MDRM. However, the potential benefit of SC in terms of appropriate empirical treatment could be only observed when MDRM were prevalent.