Bacteriocin production by Shigella sonnei isolated from faeces of children with acute diarrhoea

Abstract

Shigella is a common agent of diarrhoea, a worldwide major health problem. The bacterium produces bacteriocins; however, the role of these substances as a virulence factor is completely unknown. With the aim to search for colicin production by Shigella sonnei, to evaluate the influence of culture conditions on bacteriocin expression, and to characterize the substance partially, 16 S. sonnei strains isolated from children with diarrhoea were tested for antagonism against members of the intestinal microbiota or agents of diarrhoea. Nine strains exhibited isoantagonism and heteroantagonism against S. flexneri and diarrhoeagenic Escherichia coli. Autoantagonism and antagonism against the intestinal microbiota were not detected. Culture medium and incubation conditions influenced antagonism expression. Antagonism resulting from bacteriophages, low pH, fatty acids, hydrogen peroxide, and chloroform was excluded. The activity of the intracellular fraction obtained with 75% ammonium sulphate was preserved at pH 1.0-11.0, and was found to be reduced by organic solvents and affected by high temperatures and proteases. The antagonistic spectrum and the in vitro conditions for better antagonism expression suggest that the role of colicin in S. sonnei virulence, if any, would be expressed prior to infection, and may regulate population density of enteropathogens by helping in organism transmission.

Activity Spectrum of Colicins Produced by Shigella sonnei and Genetic Mechanism of Colicin Resistance in Conspecific S. sonnei Strains and Escherichia coli

“…In addition to the emergence of resistance, the impact of the toxin on the commensal microbiota also deserves equal attention, before therapeutic applications commence. Several studies have shown that colicins leave the structure of the commensal microbiome largely undisturbed (18,19). In our case, we found that the majority of commensal E. coli strains (85%, n ϭ 20) were colicin resistant.…”

“…Among the colicins produced by Shigella strains, colicin U and colicin Js are expressed by S. boydii and S. sonnei, respectively (15)(16)(17). A few studies have demonstrated that S. sonnei colicins exhibit antagonism against some of the shigellae and DEC, which are sometimes uncontrollable by any antimicrobial therapy (18). Hence, strategies for designing newer antibiotics with different modes of action are now being considered.…”

An evaluation and partial characterization of a bacteriocin produced by Lactococcus lactis subsp lactis ST1 isolated from goat milk

“…Oxidative stress could, in general, slightly impact the growth of LAB, since they are defined as aerotolerant microorganisms though different behavior had been detected for bacteriocin production in various atmospheric incubation conditions (7,17,19,27). …”

Colicin type 7 produced by majority of Shigella sonnei isolated from Thai patients with diarrhoea

“…Bacteriocins have been reported to be produced by several enteric bacteria including S. sonnei , S. flexneri , and S. boydii . They are usually designated as colicins (Horak 1994; Padilla et al , 2006; Smajs and Weinstock 2001; Smajs et al , 1997; Smarda et al , 1987; Sousa et al , 2010). Colicin genes are found mostly in colicinogenic plasmids of Gram-negative E. coli (Cascales et al , 2007).…”

“…There are at least 23 colicin types have been described in detail (Smajs and Weinstock 2001). It has been reported that S. sonnei , S. flexneri , and S. boydii produce colicin (Horak 1994; Padilla et al , 2006; Smajs and Weinstock 2001; Smajs et al , 1997; Smarda et al , 1987; Sousa et al , 2010); however, there are only a few reports on the characterization of bacteriocin from S. sonnei (Smarda et al , 1987; Sousa et al , 2010; Tigyi 2005). The aim of this study was to determine the colicin production by S. sonnei strain isolated from Thai patients with diarrhoea and to characterize its properties.…”