Caracterização de bacteriocina sintetizada por amostra de Shigella sonnei isolada de criança com diarreia aguda

Abstract

Shigella is one of the most important bacterial agents of acute diarrhea.Bacteriocins are antimicrobial proteinaceous substances synthesized by a huge variety of bacteria including Shigella that seem to contribute to the virulence of the organism. We addressed the characterization of a bacteriocin produced by a Shigella sonnei isolate (SsP). The activity spectrum of SsP and the distribution of the characteristic ability to synthesize bacteriocins among SsP were evaluated. MIC and MBC of the intracellular fraction precipitated with 75% (NH4)2SO4) were also determined. Molecular mass of bacteriocin(s) found in C75 was estimated by SDS-PAGE. C75 was submitted to sequential steps of chromatography and partially purified fractions were evaluated by mass spectrometry (MS). A narrow activity spectrum against taxonomically related organisms both enteropathogens and members of the intestinal microbiota was observed. The ability to express antagonism was homogeneously distributed among SsP population. CIM and CBM values as well as the short period required to eliminate the indicator strain indicated that C75 is bactericidal. Two protein bands of 57 and 66 kDa showed activity. Taken together this result, the diversity of inhibition halos sizes, and the detection of several active fractions in every purification step suggest that SsP synthesizes more than one bacteriocin. The partial purification of the bacteriocin(s) found in C75 was achieved as demonstrated by MS. Sequences obtained did not match any bacteriocin stored in the searched databases.