title: Multiple combination antibiotic susceptibility testing of nontypeable Haemophilus influenzae biofilms.
abstract: Haemophilus influenzae is a cause of otitis media with effusion (OME). Animal models demonstrate growth of H. influenzae biofilms in OME, which may explain why OME does not respond well to conventional antibiotic therapy. Using a previously developed in vitro model, we performed H. influenzae susceptibility studies to see if H. influenzae biofilm cultures were more resistant to antibiotics than planktonic (broth) cultures, and to determine which antibiotics were most effective against H. influenzae biofilms. H. influenzae isolates were grown as biofilms on polystyrene pins. Biofilm and planktonic minimum inhibitory concentrations (MICs) were measured for 8 antibiotics, and multiple combination testing was performed with 66 groupings of 1, 2, or 3 antibiotics. We found that biofilm cultures were more resistant to antibiotics than planktonic ones. Antibiotic combinations containing rifampin and ciprofloxacin were most effective against biofilms. Biofilm testing reveals differences in effectiveness among antibiotics not apparent from conventional susceptibility testing, and suggests novel antibiotic regimens that could be studied for treatment of OME.
authors.affiliation: Department of Pediatrics, Ottawa, Ontario, Canada K1H 8L1. slinger@cheo.on.ca
authors.forename: Robert
authors.initials: R
authors.lastname: Slinger
authors.forename: Francis
authors.initials: F
authors.lastname: Chan
authors.forename: Wendy
authors.initials: W
authors.lastname: Ferris
authors.forename: Sau-Wai
authors.initials: SW
authors.lastname: Yeung
authors.forename: Melissa
authors.initials: M
authors.lastname: St Denis
authors.forename: Isabelle
authors.initials: I
authors.lastname: Gaboury
authors.forename: Shawn D
authors.initials: SD
authors.lastname: Aaron
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001431:Bacteriological Techniques; D018441:Biofilms / Q000254:growth & development*; D024901:Drug Resistance, Multiple, Bacterial; D004359:Drug Therapy, Combination; D006193:Haemophilus influenzae / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D010033:Otitis Media / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents