93 Production of virulence factors by Prevotella isolates belonging to the cystic fibrosis (CF) respiratory microbiota

Abstract

Objectives The pathogenesis of Prevotella in CF lung infection is not clear. The aim of this study was to determine production of putative virulence factors by CF Prevotella isolates. Methods Prevotella isolates (CF, n=40; non-CF, n=50) were characterised phenotypically/genotypically for extended-spectrum β-lactamase (ESβL) production (Table). The presence of a capsule was determined for CF Prevotella isolates (n = 40) using both light and transmission electron microscopy. Following culture, the haemolytic capacity of cell-free supernatant from CF isolates (n = 40) was ascertained using a semi-quantitative assay. Proteolysis by Prevotella (n = 40) was investigated following growth on agar containing 2% w/v skimmed milk powder. Results ESβL production is summarised in the Table. Twenty-seven of 40 (68%) Prevotella isolates were encapsulated. All isolates (n = 40) exhibited an ability to degrade horse erythrocytes (Range, 2.07–41.95%; Mean, 23.45%) demonstrating the production of haemolysins. Protease activity was identified in 37/40 (93%) isolates. TableESBL productionPhenotypeMethodPositive, n (%)PCFNon-CFESβLCombined disc31/40 (78)27/50 (54)0.036blaTEMPCR & sequencing19/40 (48)7/50 (14)0.001 Conclusion Virulence factor production was common amongst Prevotella spp. CF Prevotella may potentially contribute to treatment failure of CF lung infection with b-lactams (ES3L production), evade the defence mechanism (capsule production) or contribute to host tissue damage (haemolysin/protease production). Funded by DEL NI studentships, HSC R&D, Public Health Agency, NI and the MRC through a US-Ireland Partnership Grant. Non-CF isolates provided by Dr Hall, Anaerobe Reference Unit, Wales.