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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.


Chlorhexidine tolerance is associated with differentially expressed genes associated with cofactor metabolism. Relative expression refers to the fold-change difference in expression between the ST24WT, without chlorhexidine treatment relative to the conditions listed in the figure.
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Figure 6: Chlorhexidine tolerance is associated with differentially expressed genes associated with cofactor metabolism. Relative expression refers to the fold-change difference in expression between the ST24WT, without chlorhexidine treatment relative to the conditions listed in the figure.

Mentions: In addition to alterations in the general cell metabolism, genes associated with cofactor synthesis in ST24WT were differentially-expressed. Six % of genes known to be associated with cofactor biosynthesis (as obtained from KEGG) were up-regulated in ST24WT, following a 30 min exposure to chlorhexidine. These markers coded for enzymes involved in the synthesis of thiamine, folate, molybdopterin and porphyrin (vitamin B12) amongst others (Figure 6). The altered expression of these cofactor associated genes may be linked with the changes in general cell metabolism outlined earlier. For example, the increased expression detected in enzymes involved in both the synthesis and transport of thiamine may be a bacterial response designed to satisfy the increased demand for thiamine as a cofactor for pyruvate dehydrogenase and 2-oxoglutarate decarboxylase. Similarly, vitamin B12 is required for the utilization of 1,2-propanediol as a carbon source by the pdu operon and molybopterin as a cofactor of formate dehydrogenase. All were up-regulated in ST24WT, following exposure to chlorhexidine (Gladyshev et al., 1994; Bobik et al., 1999).


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)

Chlorhexidine tolerance is associated with differentially expressed genes associated with cofactor metabolism. Relative expression refers to the fold-change difference in expression between the ST24WT, without chlorhexidine treatment relative to the conditions listed in the figure.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Chlorhexidine tolerance is associated with differentially expressed genes associated with cofactor metabolism. Relative expression refers to the fold-change difference in expression between the ST24WT, without chlorhexidine treatment relative to the conditions listed in the figure.
Mentions: In addition to alterations in the general cell metabolism, genes associated with cofactor synthesis in ST24WT were differentially-expressed. Six % of genes known to be associated with cofactor biosynthesis (as obtained from KEGG) were up-regulated in ST24WT, following a 30 min exposure to chlorhexidine. These markers coded for enzymes involved in the synthesis of thiamine, folate, molybdopterin and porphyrin (vitamin B12) amongst others (Figure 6). The altered expression of these cofactor associated genes may be linked with the changes in general cell metabolism outlined earlier. For example, the increased expression detected in enzymes involved in both the synthesis and transport of thiamine may be a bacterial response designed to satisfy the increased demand for thiamine as a cofactor for pyruvate dehydrogenase and 2-oxoglutarate decarboxylase. Similarly, vitamin B12 is required for the utilization of 1,2-propanediol as a carbon source by the pdu operon and molybopterin as a cofactor of formate dehydrogenase. All were up-regulated in ST24WT, following exposure to chlorhexidine (Gladyshev et al., 1994; Bobik et al., 1999).

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.