Novel toxin assays implicate Mycoplasma pneumoniae in prolonged ventilator course and hypoxemia

Abstract

Background: Community-acquired respiratory distress syndrome (CARDS) toxin is a unique Mycoplasma pneumoniae virulence factor. Molecular assays targeting this toxin are more sensitive than existing diagnostics, but these assays have not been used to investigate the role of M pneumoniae as a nosocomial infection in critical illness. We sought to determine the incidence of M pneumoniae among mechanically ventilated subjects using these novel assays and to investigate the impact of this pathogen on pulmonary outcomes. Methods: We conducted a prospective observational study enrolling subjects with suspected ventilator-associated pneumonia(VAP) undergoing BAL in the surgical trauma ICU at a level I trauma center. Lavage fluid and serum samples were tested for M pneumoniae using assays to detect CARDS toxin gene sequences, protein, or antitoxin antibodies. Results:We collected samples from 37 subjects, with 41%(15 of 37) testing positive using these assays. The positive and negative groups did not differ significantly in baseline demographic characteristics, including age, sex, injury severity, or number of ventilator days before bronchoscopy. The positive group had significantly fewer ventilator-free days(P = .04) and lower average oxygenation(P = .02). These differences were most pronounced among subjects with ARDS. Conclusions: Evidence is provided that M pneumoniae is present in a substantial number of subjects with suspected VAP. Subjects testing positive experience a significantly longer ventilator course and worse oxygenation compared with subjects testing negative. © 2011 American College of Chest Physicians.