title: Antimicrobial susceptibility of bifidobacteria.
abstract: OBJECTIVE
  The aim of our study was to analyse the antibiotic susceptibility of various strains of Bifidobacterium spp. to a wide range of antimicrobial agents.
  
  
  METHODS
  Fifty strains belonging to eight species of bifidobacteria, isolated from humans, animals or probiotic products, were tested for susceptibility to 30 antibiotics by disc diffusion on Brucella agar supplemented with 5% laked sheep blood and vitamin K1 (1 mg/L). MICs of nine anti-anaerobe agents, including three new molecules (telithromycin, linezolid and gatifloxacin), were determined using the reference agar-dilution method.
  
  
  RESULTS
  All strains of bifidobacteria, whatever the species, were sensitive to penicillins: penicillin G, amoxicillin (MIC(50) 0.06 mg/L), piperacillin, ticarcillin, imipenem and usually anti-Gram-positive antibiotics (macrolides, clindamycin, pristinamycin, vancomycin and teicoplanin). Susceptibility to cefalothin and cefotetan was variable. Most isolates (70%) were resistant to fusidic acid. As expected, high resistance rates were observed for aminoglycosides. Metronidazole, an agent known for its anti-anaerobe activity, was ineffective against 38% of the strains. The newly commercialized molecules, telithromycin, linezolid and gatifloxacin, were active with MIC(50)S of 1 mg/L. The only variation in susceptibility observed among the different species concerned Bifidobacterium breve, which appeared to be generally more resistant. Potentially acquired resistance was only observed against tetracycline and minocycline, in 14% of the strains.
  
  
  CONCLUSIONS
  With regard to a general concern about the safety of probiotics, such as potential transferability of resistance determinants, bifidobacteria, with their low natural and acquired resistance to 30 antibiotics, appear risk-free.
authors.affiliation: Laboratoire de Microbiologie, UFR des Sciences Pharmaceutiques et Biologiques, Université René Descartes, 75270 Paris, France.
authors.forename: C
authors.initials: C
authors.lastname: Moubareck
authors.forename: F
authors.initials: F
authors.lastname: Gavini
authors.forename: L
authors.initials: L
authors.lastname: Vaugien
authors.forename: M J
authors.initials: MJ
authors.lastname: Butel
authors.forename: F
authors.initials: F
authors.lastname: Doucet-Populaire
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D039941:Bifidobacteriales Infections / Q000382:microbiology; D001644:Bifidobacterium / Q000145:classification / Q000187:drug effects*; D003731:Dental Caries / Q000382:microbiology; D024881:Drug Resistance, Bacterial; D005243:Feces / Q000382:microbiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007422:Intestines / Q000382:microbiology; D008826:Microbial Sensitivity Tests / Q000379:methods; D019936:Probiotics
chemical_list: D000900:Anti-Bacterial Agents