Molecular quantification of bacteria from respiratory samples in patients with suspected ventilator-associated pneumonia

Abstract

Ventilator-associated pneumonia (VAP) is the most common infection in critically ill patients. Initial antibiotic therapy is often broad spectrum, which promotes antibiotic resistance so new techniques are under investigation to obtain early microbiological identification and quantification. This trial compares the performance of a new real-time quantitative molecular-based method with conventional culture in patients with suspected VAP. Patients with suspected VAP who were ventilated for at least 48 h were eligible. An endotracheal aspirate (ETA) and a bronchoalveolar lavage (BAL) were performed at each suspected VAP episode. Both samples were analysed by conventional culture and molecular analysis. For the latter, bacterial DNA was extracted from each sample and real-time PCR were run. In all, 120 patients were finally included; 76% (91) were men; median age was 65 years, and clinical pulmonary infection score was ≥6 for 73.5% (86) of patients. A total of 120 BAL and 103 ETA could be processed and culture results above the agreed threshold were obtained for 75.0% (90/120) of BAL and 60.2% (62/103) of ETA. The main isolated bacteria were Staphylococcus aureus, Pseudomonas aeruginosa and Haemophilus influenzae. Performance was 89.2% (83.2%-93.6%) sensitivity and 97.1% (96.1%-97.9%) specificity for BAL samples and 71.8% (61.0%-81.0%) sensitivity and 96.6% (95.4%-97.5%) specificity for ETA samples when the molecular biology method was compared with conventional culture method (chosen as reference standard). This new molecular method can provide reliable quantitative microbiological data and is highly specific with good sensitivity for common pathogens involved in VAP.

DNA‐based testing in lung transplant recipients with suspected non‐viral lower respiratory tract infection: A prospective observational study

“…Experience with BAL PCR in LTx recipients is limited to P. jirovecii and respiratory viruses, the foremost being cytomegalovirus . Unlike the clinical scenario studied herein, a multitude of studies assessing multiplex PCR in patients with suspected ventilator‐associated pneumonia argue for its usefulness in the ICU setting . None of the patients in this study, however, was transferred to the ICU, where a time difference of 2 hours might bear greater significance.…”

“…9,10 Unlike the clinical scenario studied herein, a multitude of studies assessing multiplex PCR in patients with suspected ventilator-associated pneumonia argue for its usefulness in the ICU setting. [11][12][13][14]…”

Rapid syndromic molecular testing in pneumonia: The current landscape and future potential

“…This is an FDA approved and CE marked platform that uses nested real-time PCR to detect 34 clinically important respiratory targets (15 semi-quantitative bacterial targets, 3 qualitative atypical bacterial targets, 8 resistance genes and 8 viral targets [30][31][32] Furthermore, the pneumonia panel detects pathogens in a much higher proportion of samples than culture. Buchan et al 31 reported that the Filmarray detected a bacterial target in 71% more specimens than routine culture, equating to over 100% increase in total bacterial detections.…”

Resistance Trends and Treatment Options in Gram-Negative Ventilator-Associated Pneumonia

“…Verigene is a nanoparticle-based amplification method for identifying Gram-negative species and resistance genes, but this panel is currently FDA-approved only for positive blood cultures [22]. Ribosomal amplification (e.g., 16S ribosomal RNA gene PCR) has also been evaluated in suspected VAP cases [23, 24]. …”