Differential Actions of Chlorhexidine on the Cell Wall of Bacillus subtilis and Escherichia coli

Chlorhexidine is a chlorinated phenolic disinfectant used commonly in mouthwash for its action against bacteria. However, a comparative study of the action of chlorhexidine on the cell morphology of Gram-positive and Gram-negative bacteria is lacking. In this study, the actions of chlorhexidine on the cell morphology were identified with the aids of electron microscopy. After exposure to chlorhexidine, numerous spots of indentation on the cell wall were found in both Bacillus subtilis and Escherichia coli. The number of indentation spots increased with time of incubation and increasing chlorhexidine concentration. Interestingly, the dented spots found in B. subtilis appeared mainly at the hemispherical caps of the cells, while in E. coli the dented spots were found all over the cells. After being exposed to chlorhexidine for a prolonged period, leakage of cellular contents and subsequent ghost cells were observed, especially from B subtilis. By using 2-D gel/MS-MS analysis, five proteins related to purine nucleoside interconversion and metabolism were preferentially induced in the cell wall of E. coli, while three proteins related to stress response and four others in amino acid biosynthesis were up-regulated in the cell wall materials of B. subtilis. The localized morphological damages together with the biochemical and protein analysis of the chlorhexidine-treated cells suggest that chlorhexidine may act on the differentially distributed lipids in the cell membranes/wall of B. subtilis and E. coli

New materials and devices for preventing catheter-related infections

Catheters are the leading source of bloodstream infections for patients in the intensive care unit (ICU). Comprehensive unit-based programs have proven to be effective in decreasing catheter-related bloodstream infections (CR-BSIs). ICU rates of CR-BSI higher than 2 per 1,000 catheter-days are no longer acceptable. The locally adapted list of preventive measures should include skin antisepsis with an alcoholic preparation, maximal barrier precautions, a strict catheter maintenance policy, and removal of unnecessary catheters. The development of new technologies capable of further decreasing the now low CR-BSI rate is a major challenge. Recently, new materials that decrease the risk of skin-to-vein bacterial migration, such as new antiseptic dressings, were extensively tested. Antimicrobial-coated catheters can prevent CR-BSI but have a theoretical risk of selecting resistant bacteria. An antimicrobial or antiseptic lock may prevent bacterial migration from the hub to the bloodstream. This review discusses the available knowledge about these new technologies

Identification of the Burkholderia pseudomallei bacteriophage ST79 lysis gene cassette.

AimsTo identify and characterize the lysis gene cassette from the bacteriophage ST79 that lyses Burkholderia pseudomallei.Methods and resultsApproximately 1·5 kb of ST79 lysis genes were identified from the phage genome data. It was composed of holin, peptidase M15A or endolysin, lysB and lysC. Each gene and its combinations were cloned into Escherichia coli and the lytic effects were measured. Co-expression of holin and peptidase M15A showed the highest lysis activity. Expression of holin, lysB/C or holin-peptidase M15A-lysB/lysC lysed the E. coli membrane, whereas peptidase M15A alone did not. The predicted transmembrane structures of holin and lysB/C indicated that they could be inserted into the bacterial membrane to form pores, affecting cell permeability and causing lysis.ConclusionThis is the first report of an investigation into the lysis genes of B. pseudomallei's lytic phage using E. coli as a model.Significance and impact of the studyBurkholderia pseudomallei, a Gram-negative bacterium causing an infectious disease, is intrinsically resistant to several antibiotics, and a vaccine is not available. The lysis genes of ST79, the first reported lytic bacteriophage of B. pseudomallei, were characterized. The development of ST79 as an alternative treatment for skin ulceration, for example, or to be used as a gene cloning tool for B. pseudomallei may be possible with this knowledge

Identification of the Burkholderia pseudomallei bacteriophage ST79 lysis gene cassette.

AimsTo identify and characterize the lysis gene cassette from the bacteriophage ST79 that lyses Burkholderia pseudomallei.Methods and resultsApproximately 1·5 kb of ST79 lysis genes were identified from the phage genome data. It was composed of holin, peptidase M15A or endolysin, lysB and lysC. Each gene and its combinations were cloned into Escherichia coli and the lytic effects were measured. Co-expression of holin and peptidase M15A showed the highest lysis activity. Expression of holin, lysB/C or holin-peptidase M15A-lysB/lysC lysed the E. coli membrane, whereas peptidase M15A alone did not. The predicted transmembrane structures of holin and lysB/C indicated that they could be inserted into the bacterial membrane to form pores, affecting cell permeability and causing lysis.ConclusionThis is the first report of an investigation into the lysis genes of B. pseudomallei's lytic phage using E. coli as a model.Significance and impact of the studyBurkholderia pseudomallei, a Gram-negative bacterium causing an infectious disease, is intrinsically resistant to several antibiotics, and a vaccine is not available. The lysis genes of ST79, the first reported lytic bacteriophage of B. pseudomallei, were characterized. The development of ST79 as an alternative treatment for skin ulceration, for example, or to be used as a gene cloning tool for B. pseudomallei may be possible with this knowledge