title: Activities of fosfomycin and rifampin on planktonic and adherent Enterococcus faecalis strains in an experimental foreign-body infection model.
abstract: Enterococcal implant-associated infections are difficult to treat because antibiotics generally lack activity against enterococcal biofilms. We investigated fosfomycin, rifampin, and their combinations against planktonic and adherent Enterococcus faecalis (ATCC 19433) in vitro and in a foreign-body infection model. The MIC/MBClog values were 32/>512 μg/ml for fosfomycin, 4/>64 μg/ml for rifampin, 1/2 μg/ml for ampicillin, 2/>256 μg/ml for linezolid, 16/32 μg/ml for gentamicin, 1/>64 μg/ml for vancomycin, and 1/5 μg/ml for daptomycin. In time-kill studies, fosfomycin was bactericidal at 8× and 16× MIC, but regrowth of resistant strains occurred after 24 h. With the exception of gentamicin, no complete inhibition of growth-related heat production was observed with other antimicrobials on early (3 h) or mature (24 h) biofilms. In the animal model, fosfomycin alone or in combination with daptomycin reduced planktonic counts by ≈4 log10 CFU/ml below the levels before treatment. Fosfomycin cleared planktonic bacteria from 74% of cage fluids (i.e., no growth in aspirated fluid) and eradicated biofilm bacteria from 43% of cages (i.e., no growth from removed cages). In combination with gentamicin, fosfomycin cleared 77% and cured 58% of cages; in combination with vancomycin, fosfomycin cleared 33% and cured 18% of cages; in combination with daptomycin, fosfomycin cleared 75% and cured 17% of cages. Rifampin showed no activity on planktonic or adherent E. faecalis, whereas in combination with daptomycin it cured 17% and with fosfomycin it cured 25% of cages. Emergence of fosfomycin resistance was not observed in vivo. In conclusion, fosfomycin showed activity against planktonic and adherent E. faecalis. Its role against enterococcal biofilms should be further investigated, especially in combination with rifampin and/or daptomycin treatment.
authors.affiliation: Service of Infectious Diseases, Department of Medicine, Lausanne University Hospital, Lausanne, Switzerland.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Oliva
authors.forename: Ulrika
authors.initials: U
authors.lastname: Furustrand Tafin
authors.forename: Elena Maryka
authors.initials: EM
authors.lastname: Maiolo
authors.forename: Safaa
authors.initials: S
authors.lastname: Jeddari
authors.forename: Bertrand
authors.initials: B
authors.lastname: Bétrisey
authors.forename: Andrej
authors.initials: A
authors.lastname: Trampuz
mesh_terms: D000081:Acetamides / Q000008:administration & dosage / Q000494:pharmacology; D000667:Ampicillin / Q000008:administration & dosage / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001422:Bacterial Adhesion / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects; D002151:Calorimetry; D017576:Daptomycin / Q000008:administration & dosage / Q000494:pharmacology; D004195:Disease Models, Animal; D004359:Drug Therapy, Combination; D013293:Enterococcus faecalis / Q000187:drug effects*; D005547:Foreign Bodies / Q000188:drug therapy / Q000382:microbiology*; D005578:Fosfomycin / Q000008:administration & dosage / Q000494:pharmacology*; D005839:Gentamicins / Q000008:administration & dosage / Q000494:pharmacology; D016908:Gram-Positive Bacterial Infections / Q000188:drug therapy*; D006168:Guinea Pigs; D000069349:Linezolid; D008297:Male; D008826:Microbial Sensitivity Tests; D023303:Oxazolidinones / Q000008:administration & dosage / Q000494:pharmacology; D012293:Rifampin / Q000008:administration & dosage / Q000494:pharmacology*; D014640:Vancomycin / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D000081:Acetamides; D000900:Anti-Bacterial Agents; D005839:Gentamicins; D023303:Oxazolidinones; D005578:Fosfomycin; D014640:Vancomycin; D000667:Ampicillin; D000069349:Linezolid; D017576:Daptomycin; D012293:Rifampin