Rifaximin-induced alteration of virulence of diarrhoea-producing Escherichia coli and Shigella sonnei

Rifaximin shortens the duration of travellers' diarrhoea without important alteration of colonic. ora. This study investigated the expression of virulence factors [heat-stable (ST) and heat-labile (LT) enterotoxins, surface adhesion factors (CS2/CS3, CS6) and matrix metalloproteinase-9 (MMP-9)] as well as the interleukin (IL)-8 induction potential of diarrhoeagenic Escherichia coli and Shigella sonnei strains exposed to rifaximin (8, 32 and 64 mg/L) for 4, 8, 18 and 24 h. Following exposure to rifaximin, enterotoxigenic E. coli (ETEC) isolates did not express ST/LT, CS2/CS3 or CS6, whereas enteroaggregative E. coli (EAEC) and S. sonnei isolates did not produce detectable amounts of MMP-9. Moreover, induction of IL-8 was undetectable. At subinhibitory concentrations, rifaximin alters the virulence of ETEC, EAEC and S. sonnei isolates. These findings help explain the efficacy of rifaximin despite minimal alteration of colonic. ora. (C) 2009 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.