Characterization of a bacteriocin produced by a clinical isolate of Shigella flexneri 2

Abstract

This study was conducted to determine the emergence of antibiotic resistant/producer strains, focusing the efforts in the search for new antimicrobial compounds. A total of 15,131 fecal samples (CI) were analyzed from patients from acute diarrhea (2015-2017 period) and observed that 1,794 were positive for either E. coli, Shigella or Salmonella presence. The ability of 388 Shigella isolates to produce antimicrobial peptides was determined by deferred-antagonism assay. Here, we observed that 9.02% of the Shigella isolates produced an antimicrobial agent able to inhibit the E. coli AB133 strain growth. The CI172 strain was selected as producer for its antimicrobial characterization. This antagonist compound (ShpCI172) was produced during exponential growth phase and displayed a restricted action spectrum. It is also thermo-resistant and has about 3 kDa molecular mass. The ShpCI172 can be classified as a microcin, since CI172 did not display cross immunity with other well-known microcins. This is the first report where the production of a microcin by a Shigella flexneri 2 strains is described. The use of ShpCI172 microcin may contribute to preventing or controlling diarrheal diseases. This finding represents an important contribution in the biotechnology field for its application in the development of new antibiotics and/or food preservatives agents.