Composition and antagonistic activity of the indigenous intestinal microbiota of Prochilodus argenteus Agassiz

The composition and antibacterial properties of indigenous intestinal microbiota from Prochilodus argenteus were studied during reproductive (alimentary restriction) and non‐reproductive (normal feeding) periods. Dilutions of intestinal contents from 21 specimens of P. argenteus captured from São Francisco Basin, Minas Gerais State, Brazil, were used for enumeration, isolation, identification and determination of in vitro antibacterial properties of predominant components of the intestinal microbial ecosystem. Predominant species recovered for both periods were: Aeromonas hydrophila, Plesiomonas shigelloides, Lactococcus lactis and an unidentified Gram‐positive rod for facultative anaerobes and Bacteroides stercoris/eggerthii and Fusobacterium mortiferum for obligate anaerobes. Gram‐positive components of this microbiota showed high antagonistic activity against gram‐negative species. Coagulase‐negative Staphylococcus sp., Enterococcus durans, Enterococcus faecium and the unidentified gram‐positive rod had wider range of antagonism properties. The indigenous intestinal microbiota of P. argenteus was quite similar to that of other fishes and the reproductive and alimentary status has few influences on its composition.