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Comparative analysis of Salmonella susceptibility and tolerance to the biocide chlorhexidine identifies a complex cellular defense network.

Condell O, Power KA, Händler K, Finn S, Sheridan A, Sergeant K, Renaut J, Burgess CM, Hinton JC, Nally JE, Fanning S - Front Microbiol (2014)

Bottom Line: Typhimurium compared with its isogenic sensitive progenitor.The defense network involved multiple cell targets including those associated with the synthesis and modification of the cell wall, the SOS response, virulence, and a shift in cellular metabolism toward anoxic pathways, some of which were regulated by CreB and Fur.In addition, results indicated that chlorhexidine tolerance was associated with more extensive modifications of the same cellular processes involved in this proposed network, as well as a divergent defense response involving the up-regulation of additional targets such as the flagellar apparatus and an altered cellular phosphate metabolism.

View Article: PubMed Central - PubMed

Affiliation: UCD Centre for Food Safety, School of Public Health, Physiotherapy and Population Science, University College Dublin Belfield, Dublin, Ireland ; European Program for Public Health Microbiology Training, European Centre for Disease Prevention and Control Stockholm, Sweden.

ABSTRACT
Chlorhexidine is one of the most widely used biocides in health and agricultural settings as well as in the modern food industry. It is a cationic biocide of the biguanide class. Details of its mechanism of action are largely unknown. The frequent use of chlorhexidine has been questioned recently, amidst concerns that an overuse of this compound may select for bacteria displaying an altered susceptibility to antimicrobials, including clinically important anti-bacterial agents. We generated a Salmonella enterica serovar Typhimurium isolate (ST24(CHX)) that exhibited a high-level tolerant phenotype to chlorhexidine, following several rounds of in vitro selection, using sub-lethal concentrations of the biocide. This mutant showed altered suceptibility to a panel of clinically important antimicrobial compounds. Here we describe a genomic, transcriptomic, proteomic, and phenotypic analysis of the chlorhexidine tolerant S. Typhimurium compared with its isogenic sensitive progenitor. Results from this study describe a chlorhexidine defense network that functions in both the reference chlorhexidine sensitive isolate and the tolerant mutant. The defense network involved multiple cell targets including those associated with the synthesis and modification of the cell wall, the SOS response, virulence, and a shift in cellular metabolism toward anoxic pathways, some of which were regulated by CreB and Fur. In addition, results indicated that chlorhexidine tolerance was associated with more extensive modifications of the same cellular processes involved in this proposed network, as well as a divergent defense response involving the up-regulation of additional targets such as the flagellar apparatus and an altered cellular phosphate metabolism. These data show that sub-lethal concentrations of chlorhexidine induce distinct changes in exposed Salmonella, and our findings provide insights into the mechanisms of action and tolerance to this biocidal agent.

No MeSH data available.


Related in: MedlinePlus

A 2-D proteome map of ST24WT and ST24CHX, without chlorhexidine treatment. The spot numbers corresponds to identified proteins as described in Table 2, Tables S4, S5. Those spots labeled in black represent non-differentially expressed proteins (see Table S5). Protein spots labeled green (and denoted as Group A, see Table 2, Table S4) were significantly up-regulated in ST24CHX relative to ST24WT, whilst spots labeled in red represent Group B and were significantly down-regulated in ST24CHX relative to ST24WT (Table 2, Table S4).
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Figure 8: A 2-D proteome map of ST24WT and ST24CHX, without chlorhexidine treatment. The spot numbers corresponds to identified proteins as described in Table 2, Tables S4, S5. Those spots labeled in black represent non-differentially expressed proteins (see Table S5). Protein spots labeled green (and denoted as Group A, see Table 2, Table S4) were significantly up-regulated in ST24CHX relative to ST24WT, whilst spots labeled in red represent Group B and were significantly down-regulated in ST24CHX relative to ST24WT (Table 2, Table S4).

Mentions: Proteomic analysis revealed a total of 470 protein spots differentially expressed, without chlorhexidine exposure, between ST24WT and ST24CHX (>2-fold change, p < 0.05). Among the differentially expressed proteins, 208 were up-regulated and 262 were down-regulated in ST24CHX relative to the reference isolate (Figure 8). Of the up-regulated proteins a total of 48 protein spots were identified with statistical significance and these corresponded to 34 individual proteins (Table 2, Tables S4, S5). These were divided into three functional categories; general cell metabolism (24 proteins), stress response (5 proteins) and transport and permeability (5 proteins). Up-regulated proteins are indicated in green in Figure 8, denoted by the green traces in Figure 9, and functionally categorized in Table 2.


Comparative analysis of Salmonella susceptibility and tolerance to the biocide chlorhexidine identifies a complex cellular defense network.

Condell O, Power KA, Händler K, Finn S, Sheridan A, Sergeant K, Renaut J, Burgess CM, Hinton JC, Nally JE, Fanning S - Front Microbiol (2014)

A 2-D proteome map of ST24WT and ST24CHX, without chlorhexidine treatment. The spot numbers corresponds to identified proteins as described in Table 2, Tables S4, S5. Those spots labeled in black represent non-differentially expressed proteins (see Table S5). Protein spots labeled green (and denoted as Group A, see Table 2, Table S4) were significantly up-regulated in ST24CHX relative to ST24WT, whilst spots labeled in red represent Group B and were significantly down-regulated in ST24CHX relative to ST24WT (Table 2, Table S4).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4117984&req=5

Figure 8: A 2-D proteome map of ST24WT and ST24CHX, without chlorhexidine treatment. The spot numbers corresponds to identified proteins as described in Table 2, Tables S4, S5. Those spots labeled in black represent non-differentially expressed proteins (see Table S5). Protein spots labeled green (and denoted as Group A, see Table 2, Table S4) were significantly up-regulated in ST24CHX relative to ST24WT, whilst spots labeled in red represent Group B and were significantly down-regulated in ST24CHX relative to ST24WT (Table 2, Table S4).
Mentions: Proteomic analysis revealed a total of 470 protein spots differentially expressed, without chlorhexidine exposure, between ST24WT and ST24CHX (>2-fold change, p < 0.05). Among the differentially expressed proteins, 208 were up-regulated and 262 were down-regulated in ST24CHX relative to the reference isolate (Figure 8). Of the up-regulated proteins a total of 48 protein spots were identified with statistical significance and these corresponded to 34 individual proteins (Table 2, Tables S4, S5). These were divided into three functional categories; general cell metabolism (24 proteins), stress response (5 proteins) and transport and permeability (5 proteins). Up-regulated proteins are indicated in green in Figure 8, denoted by the green traces in Figure 9, and functionally categorized in Table 2.

Bottom Line: Typhimurium compared with its isogenic sensitive progenitor.The defense network involved multiple cell targets including those associated with the synthesis and modification of the cell wall, the SOS response, virulence, and a shift in cellular metabolism toward anoxic pathways, some of which were regulated by CreB and Fur.In addition, results indicated that chlorhexidine tolerance was associated with more extensive modifications of the same cellular processes involved in this proposed network, as well as a divergent defense response involving the up-regulation of additional targets such as the flagellar apparatus and an altered cellular phosphate metabolism.

View Article: PubMed Central - PubMed

Affiliation: UCD Centre for Food Safety, School of Public Health, Physiotherapy and Population Science, University College Dublin Belfield, Dublin, Ireland ; European Program for Public Health Microbiology Training, European Centre for Disease Prevention and Control Stockholm, Sweden.

ABSTRACT
Chlorhexidine is one of the most widely used biocides in health and agricultural settings as well as in the modern food industry. It is a cationic biocide of the biguanide class. Details of its mechanism of action are largely unknown. The frequent use of chlorhexidine has been questioned recently, amidst concerns that an overuse of this compound may select for bacteria displaying an altered susceptibility to antimicrobials, including clinically important anti-bacterial agents. We generated a Salmonella enterica serovar Typhimurium isolate (ST24(CHX)) that exhibited a high-level tolerant phenotype to chlorhexidine, following several rounds of in vitro selection, using sub-lethal concentrations of the biocide. This mutant showed altered suceptibility to a panel of clinically important antimicrobial compounds. Here we describe a genomic, transcriptomic, proteomic, and phenotypic analysis of the chlorhexidine tolerant S. Typhimurium compared with its isogenic sensitive progenitor. Results from this study describe a chlorhexidine defense network that functions in both the reference chlorhexidine sensitive isolate and the tolerant mutant. The defense network involved multiple cell targets including those associated with the synthesis and modification of the cell wall, the SOS response, virulence, and a shift in cellular metabolism toward anoxic pathways, some of which were regulated by CreB and Fur. In addition, results indicated that chlorhexidine tolerance was associated with more extensive modifications of the same cellular processes involved in this proposed network, as well as a divergent defense response involving the up-regulation of additional targets such as the flagellar apparatus and an altered cellular phosphate metabolism. These data show that sub-lethal concentrations of chlorhexidine induce distinct changes in exposed Salmonella, and our findings provide insights into the mechanisms of action and tolerance to this biocidal agent.

No MeSH data available.


Related in: MedlinePlus