Transcriptomic Response Of Salmonella Enterica Subspecies Enterica Serovar Typhi To Antibiotic Treatments During Biofilm Formation
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Date
2018-03
Authors
Dashti, Marjan Ganjali
Journal Title
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Publisher
Universiti Sains Malaysia
Abstract
Salmonella Typhi (S. Typhi) is a human-specific pathogen which causes typhoid fever. One major factor contributing to typhoid persistence is the existence of asymptomatic typhoid carriers. Biofilm formation in the human gallbladder is postulated to be associated with development of the carrier-state. The aim of this study was to develop an optimized assay for S. Typhi biofilm formation in vitro that mimics the environment of the gallbladder. Six key variables involved in S. Typhi biofilm formation were optimized using Response Surface Methodology (RSM), and the resulting assay formed the basis for transcriptomic investigation of biofilm production, in the presence of the antibiotics kanamycin and chloramphenicol. Both planktonic (free-swimming) and intermediate-biofilm cells were investigated in this study, to determine the patterns of gene expression which influence the S. Typhi biofilm community. The results showed that S. Typhi could not survive antibiotic treatment in the absence of biofilm. The bacteria were found to construct biofilm more readily in the presence of kanamycin than chloramphenicol. To clarify the mechanism of this adaptation, high quality RNA was extracted from untreated and antibiotic-treated samples of S. Typhi planktonic and intermediate-biofilm cells. Transcriptomic analysis was carried out to identify genes responsible for the adaptation. Gene expression of S. Typhi cells were grouped into four categories: 1) biofilm regulation, 2) exopolysaccharide and lipopolysaccharide production, 3) antibiotic resistance, and 4) metabolic pathways. Four genes involved in biofilm formation were selected and confirmed using qualitative real-time PCR (qPCR). It was established that the Multiple-stress-resistance gene bhsA was up-regulated in the intermediate-biofilm cells with chloramphenicol and kanamycin treatments.
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Keywords
S. Typhi biofilm formation in vitro , environment of the gallbladder