Toxin production, adherence and protein expression by clinicalAeromonasspp. isolates in broth and human pooled ileostomy fluid

Abstract

SUMMARYThe physiological behaviour of clinicalAeromonasspp. isolates was compared following culture in a conventional broth and human pooled ileostomy fluid (PIF). Protein expression was markedly affected by the growth medium, with an overall reduction in whole cell proteins in bacteria grown in ileostomy fluid. In addition, novel outer membrane proteins were produced in PIF but not in broth. The majority ofA. hydrophilaandA. sobriaisolates produced toxin in both broth and PIF. whereas no cytotoxin positiveA. caviaewere found. Toxin titres were at least two doubling dilutions higher in 40% and 21% ofA. hydrophilaandA. sobriaisolates, respectively, following culture in brain heart infusion broth compared with PIF. Bacterial adherence to Vero and A-549 cells was significantly more common inA. hydrophila(53%) andA. sobria(64%) than inA. caviae(15%) (P < 0·01). We observed increased adherence 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 virulence determinants byAeromonasspp. provides a rationale for the use of human ileostomy fluid in futurein vitrostudies, in order to simulate the nutrient conditions foundin vivo.