title: Mechanistic insights into response of Staphylococcus aureus to bioelectric effect on polypyrrole/chitosan film.
abstract: Treatment of biofilm-related infections in orthopedics remains a serious clinical challenge. It is known that an electric current can significantly enhance the potency of some antibiotics against biofilms (bioelectric effect) but the uncertainty of the mechanisms and the electrolytic cell-like system used in previous studies limit its applications. Herein, the behavior of Staphylococcus aureus (S. aureus) on an electrically conductive polypyrrole/chitosan film upon passage of a direct current (DC) through the film was investigated in the absence and presence of gentamicin. The killing efficacy of the bacteria within the biofilm by gentamicin was greatly enhanced by the DC treatment. From an analysis of the gene expression by the biofilm bacteria after treatment with gentamicin, DC and their combination, it is postulated that the promotion of bacterial autolysis by DC treatment is responsible for the enhanced susceptibility of biofilm S. aureus to gentamicin. This postulate is supported by an increase in the amount of extracellular deoxyribonucleic acid and adenosine triphosphate, and the appearance of disrupted bacterial cells in the biofilm after DC treatment. These findings provide a new insight into the interaction between DC and bacteria, and offer potential benefits for the treatment of infections in orthopedics.
authors.affiliation: NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Kent Ridge 117576, Singapore.
authors.forename: Jieyu
authors.initials: J
authors.lastname: Zhang
authors.affiliation: NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Kent Ridge 117576, Singapore; Department of Chemical and Biomolecular Engineering, National University of Singapore, Kent Ridge 117576, Singapore. Electronic address: chenkg@nus.edu.sg.
authors.forename: Koon Gee
authors.initials: KG
authors.lastname: Neoh
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, Kent Ridge 117576, Singapore.
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Hu
authors.affiliation: NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Kent Ridge 117576, Singapore; Department of Chemical and Biomolecular Engineering, National University of Singapore, Kent Ridge 117576, Singapore.
authors.forename: En-Tang
authors.initials: ET
authors.lastname: Kang
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001422:Bacterial Adhesion / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D048271:Chitosan / Q000494:pharmacology*; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000378:metabolism; D004560:Electricity; D005110:Extracellular Space / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005839:Gentamicins / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D010933:Plankton / Q000187:drug effects / Q000254:growth & development; D011108:Polymers / Q000494:pharmacology*; D011758:Pyrroles / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000166:cytology / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D004269:DNA, Bacterial; D005839:Gentamicins; D011108:Polymers; D011758:Pyrroles; C067635:polypyrrole; D000255:Adenosine Triphosphate; D048271:Chitosan
keywords: Autolysis; Bioelectric effect; Biofilm; Direct current; Gentamicin; Staphylococcus aureus