Concordance between a new molecular real-time approach and traditional culture in suspected VAP patients

Introduction

Early microbiological documentation may reduce attributable mortality and excessive use of broad-spectrum antibiotics in ventilator-associated pneumonia (VAP). Using bronchoalveolar lavage (BAL) and endotracheal aspirates (ETA), we studied a new molecular biology-based approach to detect and quantify bacteria in less than 3 hours. This prospective multicenter trial aimed at comparing the microbiological results obtained using this molecular protocol (easyMAG® system) and semiquantitative culture in suspected VAP.

Methods

ETA and BAL samples were consecutively collected during 10 months in adult patients in four ICUs of France. The molecular method includes a preprocessing liquefaction for ETA before DNA extraction. DNAs were extracted using the easyMAG® system. Real-time PCR (qPCR) was run using the ABI7500FastDx PCR instrument. The results presented here concern: Staphylococcus aureus, Pseudomonas aeruginosa and Enterobacteriaceae. Quantification was performed using qPCR standard curves, by converting the cycle threshold to CFU/ ml.

Results

A total of 125 suspected VAP were included from 122 patients. In total, 125 BAL and 107 ETA were collected. Sex ratio (M/F) was 76%, and CPIS ≥6 was calculated in 74.6% of the suspected VAP patients. Mean ventilation duration before sampling was 6 days. Seventy-eight percent and 65% of the BAL and ETA culture were positive respectively. Correlations between molecular method and culture on BAL and ETA are reported in Table 1.

Table 1 Concordance between qPCR and culture on BAL/ETA in VAP patients.

Conclusion

Sensitivity and specificity of the new molecular approach for these main bacteria found in VAP could enable targeted first-line antibiotic therapy. In the future, the development of this approach will aim at obtaining a bedside diagnostic in only a few hours.