title: Inefficacy of vancomycin and teicoplanin in eradicating and killing Staphylococcus epidermidis biofilms in vitro.
abstract: Biofilm-associated bacteria display a decreased susceptibility towards antibiotics. Routine assessment of antibiotic susceptibility of planktonic bacteria therefore offers an insufficient prediction of the biofilm response. In this study, in vitro biofilms of eight clinical Staphylococcus epidermidis strains were subjected to treatment with vancomycin, teicoplanin, oxacillin, rifampicin and gentamicin. In addition, the biofilms were subjected to combinations of an antibiotic with rifampicin. The effects on the biofilms were assessed by crystal violet staining to determine the total biofilm biomass, staining with XTT to determine bacterial cell viability, and microscopy. Combining these methods showed that treatment of S. epidermidis biofilms with glycopeptides increased the total biofilm biomass and that these antibiotics were not effective in killing bacteria embedded in biofilms. The decreased killing efficacy was more pronounced in biofilms produced by strains that were classified as 'strong' biofilm producers. Rifampicin, oxacillin and gentamicin effectively killed biofilm-associated bacteria of all tested strains. Combining antibiotics with rifampicin increased the killing efficacy without influencing the total biofilm biomass. When vancomycin or teicoplanin were combined with rifampicin, the increase in biofilm biomass was neutralised and also the killing efficacy was influenced in a positive way. We conclude that the combined methodology used in this study showed that glycopeptides were not effective in eradicating S. epidermidis biofilms but that combination with rifampicin improved the killing efficacy in vitro.
authors.affiliation: KU Leuven-University of Leuven, Department of Microbiology and Immunology, Laboratory of Clinical Bacteriology and Mycology, UZ Leuven Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium. Electronic address: jolien_cl@hotmail.com.
authors.forename: J
authors.initials: J
authors.lastname: Claessens
authors.affiliation: KU Leuven-University of Leuven, Department of Microbiology and Immunology, Laboratory of Clinical Bacteriology and Mycology, UZ Leuven Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
authors.forename: M
authors.initials: M
authors.lastname: Roriz
authors.affiliation: KU Leuven-University of Leuven, Department of Microbiology and Immunology, Laboratory of Clinical Bacteriology and Mycology, UZ Leuven Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
authors.forename: R
authors.initials: R
authors.lastname: Merckx
authors.affiliation: Electron Microscopy Facility (EMoNe) of the VIB BIO Imaging Core at KU Leuven-University of Leuven, Center for Human Genetics, Herestraat 49, B-3000 Leuven, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Baatsen
authors.affiliation: KU Leuven-University of Leuven, Department of Microbiology and Immunology, Laboratory of Molecular Bacteriology, Rega Institute for Medical Research, Herestraat 49, B-3000 Leuven, Belgium.
authors.forename: L
authors.initials: L
authors.lastname: Van Mellaert
authors.affiliation: KU Leuven-University of Leuven, Department of Microbiology and Immunology, Laboratory of Clinical Bacteriology and Mycology, UZ Leuven Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Van Eldere
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development*; D004347:Drug Interactions; D005839:Gentamicins / Q000494:pharmacology; D006801:Humans; D050296:Microbial Viability / Q000187:drug effects*; D010068:Oxacillin / Q000494:pharmacology; D012293:Rifampin / Q000494:pharmacology; D013203:Staphylococcal Infections / Q000382:microbiology; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000302:isolation & purification / Q000502:physiology; D017334:Teicoplanin / Q000494:pharmacology*; D014640:Vancomycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D005839:Gentamicins; D017334:Teicoplanin; D014640:Vancomycin; D010068:Oxacillin; D012293:Rifampin
keywords: Biofilm; Biofilm biomass; Killing efficacy; Staphylococcus epidermidis; Teicoplanin; Vancomycin