TOXIN PRODUCTION, ADHERENCE AND PROTEIN EXPRESSION BY CLINICAL AEROMONAS SPP ISOLATES IN BROTH AND HUMAN POOLED ILEOSTOMY FLUID

The physiological behaviour of clinical Aeromonas spp. isolates was co mpared following culture in a conventional broth and human pooled ileo stomy fluid (PIF). Protein expression was markedly affected by the gro wth medium, with an overall reduction in whole cell proteins in bacter ia grown in ileostomy fluid. In addition, novel outer membrane protein s were produced in PIF but not in broth. The majority of A. hydrophila and A. sobria isolates produced toxin in both broth and PIF, whereas no cytotoxin positive A. caviae were found. Toxin titres were at least two doubling dilutions higher in 40% and 21% of A. hydrophila and A. sobria isolates, respectively, following culture in brain heart infusi on broth compared With PIF. Bacterial adherence to Vero and A-549 cell s was significantly more common in A. hydrophila (53%) and A. sobria ( 64%) than in A. caviae (15%) (P < 0.01). We observed increased adheren ce by 6 aeromonas strains previously classified as adherence-positive, but not by 6 non-adherers, in PIF compared with brain heart infusion broth. The influence of growth medium on the expression of potential v irulence determinants by Aeromonas spp. provides a rationale for the u se of human ileostomy fluid in future in vitro studies, in order to si mulate the nutrient conditions found in vivo.