Characterisation of a type IV pilus produced by Aeromonas caviae

A pilus produced by a clinical isolate of Aeromonas caviae (strain CA195) was purified and partially characterised. The Mr of the pilin was estimated to be 23 kDa by SDS-PAGE. Its N-terminal amino-acid sequence showed that it was closely related to 'bundle-forming' type IV pili purified from other Aeromonas spp. associated with gastro-enteritis and considered to be important intestinal colonisation factors. Bundle-forming pili, often with a polar location, were seen on the surface of strain CA195 which was highly adherent to HEp-2 cells. Removal of surface structures by mechanical means decreased adhesion (by > or = 50%) suggesting that these pili played some role in HEp-2 cell binding. This pilus type could prove an important marker for enteropathogenic A. caviae which appear to lack other putative virulence factors.