Adaptation of prevotella during acute infectious pulmonary exacerbation

Introduction: Prevotella species are the predominant anaerobes detected in sputum samples from CF patients. Little is known about how these organisms survive interaction with the influx of immune components that occurs during pulmonary inflammation. Therefore, this study aimed to determine if the resistance of these organisms to the bactericidal activities of neutrophils and/or the complement system increased during CF pulmonary exacerbation Methods: Prevotella isolates, highly similar by PFGE, were cultured from 2 CF patients prior to and immediately after antibiotic treatment of an infective pulmonary exacerbation. The 4 isolates were incubated with pooled human serum (t=60 mins), which contains complement, and with human neutrophils (t=20 mins). Decreases in bacterial cell viability were calculated relative to controls performed in the absence of the respective immune components Results: Table 1 . Activity of immune components against Prevotella % Survival in Serum +/- SD (N=3) % Survival in Neutrophils +/- SD (N=3) Patient (Gender & Age) Pre-Ex Post-Ex Pre-Ex Post-Ex Patient 1 (M, 25) 42.6 (+/- 4.3) 60.4 (+/- 7.2) --- --- Patient 2 (F, 21) 22.2 (+/- 4.0) 95.6 (+/- 3.1) 64.5 (+/-2.1) 64.9 (+/-2.9) Pre-Ex: organism isolated pre-exacerbation; Post-Ex: organism isolated post-exacerbation Post exacerbation isolates were significantly more resistant to the bactericidal effects of human serum (P < 0.05). Susceptibility to neutrophil mediated killing was similar Conclusion: Resistance of Prevotella species to complement mediated immune clearance increases during pulmonary exacerbation. Up-regulation of this key virulence determinant may reflect adaptation to prolonged exposure to complement during pulmonary exacerbation.