Clinical impact of multiplex bacterial PCR of bronchoalveolar lavage in patients with suspected LRTI

Introduction: Lower respiratory tract infections (LRTI) are a major cause of morbidity and mortality in patients worldwide. Early pathogen identification is crucial to guide antibacterial therapy and decrease length of hospital stay. Methods: Prospective, monocentric, clustered, observational study. Patients with suspected LRTI who underwent bronchoscopy with bronchoalveolar lavage (BAL) over 12 months were included. In addition to conventional microbiology, a multiplex polymerase chain reaction (PCR) bacterial assay (Curetis Unyvero) was performed in the BAL on a 2 week on:1 week off predetermined schedule. No therapeutic recommendation was provided in conjunction with the PCR results to the treating physician. Primary outcome was usage of antibacterial therapy within 30 days after the bronchoscopy. Results: 605 cases (330 immunosuppressed) were analyzed. When taking into consideration only the 17 pathogens included in the multiplex PCR assay, there was 100% concordance for positive results between the multiplex PCR assay and conventional culture in 58/107 cases. For negative results, the concordance was 294/311 cases. Thus, conventional culture detected only 54% of the bacteria evidenced by PCR in the BAL. However, PCR failed to detect bacteria in 5.5% of the cases with a positive culture. After bronchoscopy, 57% (208/368) of the hospitalized patients received antibacterial therapy for LRTI, with an average of 2.1 ± 1.1 antibacterial agents per case used for a median of 10 [6; 14] days. The cases with multiplex PCR results did not have a statistically significant difference in antibacterial therapy length after bronchoscopy (p = 0.133), amount of antibiotics used after bronchoscopy (p = 0.357) or hospital stay (p = 0.696) compared to cases with only culture results. Conclusion: PCR detected 50% more bacteria in the BAL than conventional culture. Without a specific action plan for the treating physician, PCR results of the BAL did not influence antibiotic usage in patients with suspected LRTI.