95 Susceptibility of CF Prevotella isolates to neutrophil and complement mediated immune clearance

Objectives Prevotella spp. are the predominant anaerobes detected in CF sputum samples. To contribute to disease development bacteria, such as Prevotella, must first survive the host's immune response. Therefore, this study aimed to determine the susceptibility of CF Prevotella isolates to neutrophil and complement mediated immune clearance. Methods Prevotella spp. (N = 8) isolated from CF patients (N = 8) were incubated with neutrophils from healthy controls (T = 20 mins) and with serum complement (T = 60 mins). Decreases in bacterial viability were calculated relative to controls. Prevotella and P. aeruginosa co-culture neutrophil killing assays were also performed. TableSurvival of isolatesSpecies% Survival in 10% serum (N = 3), mean±SD%Survival in neutrophils (N = 3), mean±SD% Survival of P. aeruginosa, co-cultured with Prevotella, in neutrophils (N = 3), mean±SDP. denticola100.5±6.4 * 66.13±4.1644.74±10.56P. salivae42.64±4.24114.3±15.04 * 43.05±2.28P. nigrescens70.9±6.9967.848.19±3.17P. veroralis61.72±20.130.69±8.31−P. melaninogenica3.84±1.0961.43±6.066.80±3.26P. histicola08.19±2.68−P. pallens113.3±9.43 * 23.33±5.77−P. oulorum101.6±5.4 * 46.03±8.56−*Resistant. Results See the table. Prevotella isolates displayed resistance to serum killing (N = 3) and phagocytosis (N = 1). Four Prevotella isolates were more resistant to phagocytosis (>60% survival) than P. aeruginosa and S. aureus (∼42 and 54% survival, respectively). When co-cultured with P. melaninogenica, the resistance of P. aeruginosa to phagocytosis increased (P = 0.001). Conclusion Complement resistance & neutrophil evasion/inhibition strategies utilised by Prevotella spp. may enable persistence within the CF lung.