Molecular detection of microorganisms in distal airways of patients undergoing lung cancer surgery

Abstract

Background: Whereas proximal airways of patients undergoing lung cancer surgery are known to present specific microbiota incriminated in the occurrence of postoperative respiratory complications, little attention has been paid to distal airways and lung parenchyma considered to be free from bacteria. We have hypothesized that molecular culture-independent techniques applied to distal airways should allow identification of uncultured bacteria, virus, or emerging pathogens and predict the occurrence of postoperative respiratory complications.

Methods: Microbiological assessments were obtained from the distal airways of resected lung specimens from a prospective cohort of patients undergoing major lung resections for cancer. Microorganisms were detected using real-time polymerase chain reaction (PCR) assays targeting the bacterial 16s ribosomal RNA gene and Herpesviridae, cytomegalovirus (CMV), and herpesvirus simplex. All postoperative microbiological assessments were compared with the PCR results.

Results: In all, 240 samples from 87 patients were investigated. Colonizing agents were exclusively Herpesviridae (CMV, n=13, and herpesvirus simplex, n=1). All 16s ribosomal RNA PCR remained negative. Thirteen patients (15%) had a positive CMV PCR (positive-PCR group), whereas the remaining 74 patients constituted the negative-PCR group. Postoperative pneumonia occurred in 24% of the negative-PCR group and in 69% of the positive-PCR group (p=0.003). Upon stepwise logistic regression, performance status, percent of predicted diffusion lung capacity for carbon monoxide, and positive PCR were the risk factors of postoperative respiratory complications. The CMV PCR had a positive predictive value of 0.70 in prediction of respiratory complications.

Conclusions: When tested by molecular techniques, lung parenchyma and distal airways are free of bacteria, but CMV was found in a high proportion of the samples. Molecular CMV detection in distal airways should be seen as a reliable marker to identify patients at risk for postoperative respiratory complications.