Evaluación de extractos acuosos de Annona lutescens Safford (Annonaceae) contra Escherichia coli Escherich, 1885 (Enterobacteriaceae)

Abstract

Annona lutescens Safford es un árbol con diversas actividades biológicas tales como: analgésico, antitumoral, vermífugo, insecticida y antibacteriana; sin embargo, se desconoce si muestra actividad sobre las variantes patógenas de E. coli, un bacilo Gramnegativo que causa diarrea. Los ensayos in vitro mostraron que E. coli ATCC 25922 fue inhibida de manera dosis dependiente con los extractos acuosos de hojas de A. lutescens. Dichos extractos no inhibieron las variantes patógenas de E. coli EAEC, DAEC o EPEC, que causan diarrea; tampoco degradó a la proteína Pic, un factor de virulencia de EAEC.

Annona lutescens Safford is a small tree in which crude extracts have demonstrated biological activities including analgesic, anti-tumoral, vermifuge, in- secticide and antibacterial; however, this biological activity against diarrheagenic E. coli strains have not been evaluated. In vitro assays performed in this study demonstrate that leaf crude aquose extracts of A. lutescens exhibited antibacterial activity against the non-pathogenic E. coli strain ATCC 25922 in a dose-dependent manner. The extracts, however, were unable to inhibit the bacterial growth when incubated with diarrheagenic pathotypes EAEC, DAEC, or EPEC. The crude extract was tested for protease activity on secreted virulence factors. A secreted autotransporter protein, Pic, an important virulence factor from EAEC, was used as a surrogate for this studies but Pic remained intact after incubation.