Effect of simulated gastrointestinal conditions on biofilm formation by Salmonella 1,4,[5],12:i:-.

R Seixas,L Tavares,F Bernardo,M Oliveira,M Gabriel,J Machado

doi:10.1155/2014/153956

Abstract

Salmonella Typhimurium 1,4,[5],12:i:- is a major serovar responsible for human salmonellosis whose biofilm-forming ability, influenced by environmental conditions like those found in the gastrointestinal tract, is one of the main contributing factors to its ability to persist in the host and thus one of the main causes of chronic relapsing infections. Most studies to evaluate biofilm formation are performed in microtiter assays using standard media. However, no reports are available on the ability of this serovar to produce biofilm under in vitro simulated gastrointestinal conditions which better correlate with the environment found in the gastrointestinal tract. To address this, a modified biofilm assay simulating intestinal fluid was conceived to assess the biofilm formation of 133 Salmonella Typhimurium 1,4,[5],12:i:- isolates with and without agitation and at three different time points (24 h, 48 h, and 72 h). The results were then compared to the existing microtiter method using conventional biofilm growth medium (Mueller Hinton Broth). Statistical analysis revealed significant differences in the results obtained between the three protocols used. The simulated human intestinal environment impaired biofilm production demonstrating that conditions like pH, agitation or the presence of enzymes can influence biofilm production. Therefore, results from in vitro simulation of in vivo conditions may contribute to unravelling factors relating to biofilm formation and persistence in the context of the human host.

Highlights

The emergence of a pandemic monophasic variant of Salmonella Typhimurium, S. enterica subsp. enterica serovar 1,4,[5],12:i:, was first reported in Europe in the mid-1990s and is presently considered to be one of the major serovars responsible for human salmonellosis worldwide [1].Many studies have demonstrated that Salmonella bacteria are capable of forming biofilms on a wide variety of abiotic and biotic surfaces [2, 3]
We aimed to evaluate the influence of conditions mimicking the intestinal human tract environment on biofilm formation by Salmonella Typhimurium 1,4,[5],12:i:- in vitro
With these modifications, which better simulate real conditions, we aim to provide a better insight into the influence the gastrointestinal environment has upon the biofilm-forming ability of this serovar and provide more reliable laboratory and clinically relevant results

Summary

Introduction

Many studies have demonstrated that Salmonella bacteria are capable of forming biofilms on a wide variety of abiotic and biotic surfaces [2, 3]. These highly organized multicellular bacterial structures, responsible for chronic or persistent infections, decrease antimicrobial therapy efficacy and improve resistance to environmental stresses such as desiccation, high temperatures, and antiseptics [4, 5]. Modifications have been made to improve its accuracy [8, 9] It is generally performed under static conditions using different media, such as Mueller Hinton Broth (MHB) or Tryptic Soy Broth (TSB), and enables quantitative biofilm determination through the application of different dyes such as crystal violet, resazurin, or dimethyl methylene blue [7, 8]

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