Effect of triclosan onSalmonella typhimuriumat different growth stages and in biofilms

Abstract

Triclosan is a potent biocide that is included in a diverse range of products. This research was aimed to investigate the susceptibility of planktonic and biofilm-associated Salmonella enterica serovar Typhimurium to triclosan, and to identify potential mechanisms of adaptation. The effect of triclosan was studied on planktonic Salmonella (log and stationary phases), on biofilm-associated cells, on bacteria derived from disrupted biofilms and on a biofilm-deficient mutant. An eight-log reduction of exponentially growing cells was observed with 1000 micro g mL(-1) triclosan within 10 min, a 3.6-log reduction in stationary cells and a 6.3-log reduction in stationary cells of a biofilm-deficient mutant (P<0.05). Biofilm-associated cells were tolerant (1-log reduction). However, biofilm-derived cells showed sensitivity to triclosan similar to stationary-phase cells. Triclosan induced the transcription of fabI and micF. Within biofilms, triclosan also up-regulated the transcription of acrAB, encoding for an efflux pump, marA, and the cellulose-synthesis-coding genes bcsA and bcsE. Thus, Salmonella within biofilms could experience reduced influx, increased efflux and enhanced exopolysaccharides production. Our results demonstrated that the tolerance of Salmonella towards triclosan in the biofilm was attributed to low diffusion through the extracellular matrix, while changes of gene expression might provide further resistance to triclosan and to other antimicrobials.

The Challenge of Efflux-Mediated Antibiotic Resistance in Gram-Negative Bacteria

“…The impact of drug exporters on biofilm formation varies in different species, so P. aeruginosa mutants deficient in or overproducing RND pumps can still form biofilms (16,884), while the loss or inhibition of any of 9 MDR pumps (AcrAB, AcrD, AcrEF, MdtABC, MdsABC, EmrAB, MdfA, MdtK, and MacAB) or the TolC OM protein in Salmonella impairs biofilm formation with reduced production of curli (885,886). Interestingly, the biocide triclosan induces acrAB and marA expression in Salmonella biofilm cells (887). Similarly, E. coli mutants with a genetic deletion of one of the RND (acrAB, acrD, acrEF, mdtABC, and mdtEF), MFS (emrAB, emrD, and emrKY), SMR (emrE), and ABC (macAB) pump genes resulted in reduced biofilm formation (888).…”

Signals, Regulatory Networks, and Materials That Build and Break Bacterial Biofilms

“…Subinhibitory concentrations of the aminoglycoside antibiotic tobramycin has been shown to induce biofilm formation in P. aeruginosa (135). Another antimicrobial compound, triclosan, enhances transcription of cellulose synthesis genes in S. Typhimurium (310). Because cellulose is part of the biofilm matrix of S. Typhimurium, triclosan may activate biofilm formation in this organism.…”

The RNA Processing Enzyme Polynucleotide Phosphorylase Negatively Controls Biofi lm Formation by Repressing Poly-N-Acetylglucosamine (PNAG) Production in Escherichia coli C

“…Triclosan also caused upregulated the transcription of other genes (e.g. micF, acrAB, marA bcsA, bcsE) in Salmonella that might help induce further resistance [16]. Schweizer [17] reported that some bacterial strains (such as gram-negative bacteria) use a multiple triclosan resistance mechanism, including active efflux from cell where bacteria actively pump TCS out of the cell [18].…”