title: Extracellular DNA-dependent biofilm formation by Staphylococcus epidermidis RP62A in response to subminimal inhibitory concentrations of antibiotics.
abstract: We measured the ability of Staphylococcus epidermidis to form biofilms in the presence of subminimal inhibitory concentrations (sub-MICs) of vancomycin, tigecycline, linezolid and novobiocin. Six strains that produce different amounts of biofilm were tested. The three strains that produced the highest amounts of biofilm exhibited steady-state or decreased biofilm formation in the presence of sub-MIC antibiotics, whereas the three strains that produced lower amounts of biofilm exhibited up to 10-fold-increased biofilm formation in the presence of sub-MIC antibiotics. In two of the inducible strains (9142 and 456a), antibiotic-induced biofilm formation was inhibited by dispersin B, an enzyme that degrades poly-N-acetylglucosamine (PNAG) biofilm polysaccharide. In the third inducible strain (RP62A), dispersin B inhibited biofilm formation in response to sub-MIC vancomycin, but not to sub-MIC tigecycline. In contrast, DNase I efficiently inhibited biofilm formation by strain RP62A in response to sub-MIC tigecycline and vancomycin. DNase I had no effect on antibiotic-induced biofilm formation in strains 9142 and 456a. Our findings indicate that antibiotic-induced biofilm formation in S. epidermidis is both strain- and antibiotic-dependent and that S. epidermidis RP62A utilizes an extracellular DNA-dependent mechanism to form biofilms in response to sub-MIC antibiotics.
authors.affiliation: Department of Oral Biology, New Jersey Dental School, Medical Science Building, Room C636, 185 S. Orange Ave., Newark, NJ 07103, USA. kaplanjb@umdnj.edu
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Kaplan
authors.forename: Saïd
authors.initials: S
authors.lastname: Jabbouri
authors.forename: Irina
authors.initials: I
authors.lastname: Sadovskaya
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D013045:Species Specificity; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial