Comparison of the surveillance with quantitative and nonquantitative ETA cultures in predicting ventilator-associated pneumonia etiology in patients receiving antibiotic therapy

Introduction

It is not yet clear whether surveillance of lower respiratory tract secretions should be performed routinely and which method should be used for this. The aim of the present study is to investigate the value of quantitative (QC-ETA) and nonquantitative (NQC-ETA) surveillance cultures in predicting the causative pathogen of ventilator-associated pneumonia (VAP) in patients receiving antibiotic therapy.

Methods

A prospective, observational, cohort study carried out in medical ICU of a tertiary hospital. One hundred and nine ICU patients receiving mechanical ventilation for at least 4 days were included in the study.

Results

Concordance and discordance of causative pathogens of VAP with prior quantitative and nonquantitative surveillance cultures were assessed. Tracheal surveillance cultures were obtained routinely at the time of intubation and thrice weekly. Each sample was processed nonquantitatively and quantitatively (103 and 105 cfu/ml). Diagnosis of VAP was made with microbiologically confirmed clinical criteria (CPIS > 6 and growth > 105 cfu/ml in ETA). Sixty-eight VAP episodes were developed during this period. Sensitivity (63%, 28%), specificity (78%, 85%), positive predictive value (82%, 76%), negative predictive value (56%, 41%), false positive (22%, 15%) and false negative (37%, 72%) results of the NQC-ETA and QC-ETA were calculated, respectively. NQC-ETA and QC-ETA predicted the causative pathogens 3.3 (2.7) days and 2.5(1.7) days prior to the development of VAP episodes, respectively.

Conclusion

The results of this study suggest that NQC-ETA would be an acceptable tool in surveillance for and predicting the causative pathogen of VAP developing in patients who have already received antibiotic therapy.