title: Importance of antibiotic penetration in the antimicrobial resistance of biofilm formed by non-pigmented rapidly growing mycobacteria against amikacin, ciprofloxacin and clarithromycin.
abstract: OBJECTIVE
  To study the resistance of biofilms developed by non-pigmented rapidly growing mycobacteria (NPRGM) against amikacin, ciprofloxacin and clarithromycin in an in vitro model using clinical strains of different species.
  
  
  METHODS
  Antimicrobial susceptibilities of different clinical strains of Mycobacterium abscessus, Mycobacterium chelonae, Mycobacterium fortuitum, Mycobacterium peregrinum, Mycobacterium mucogenicum and Mycobacterium mageritense using conventional techniques were measured. Biofilm resistance was measured by using the sandwich technique developed by Anderl et al. using a concentration of antibiotic of 50mg/L. Penetration of antibiotics through biofilm was measured using the same technique with minimal modifications.
  
  
  RESULTS
  NPRGM biofilms showed drug resistance (percentages of viable bacteria >1% of those of controls) against antibiotics that are commonly used for the treatment of infections caused by these organisms, although there are intraspecies differences between strains. We have detected differences in antibiotic penetration through biofilms with an important permeability barrier for ciprofloxacin. However, other mechanisms must be probably more important to explain the antimicrobial resistance of NPRGM biofilm.
  
  
  CONCLUSIONS
  Biofilms formed by NPRGM are resistant to amikacin, ciprofloxacin and clarithromycin. As no resistance differences between the tested antibiotics have been observed, it is likely that biofilm permeability of antibiotics is of low importance for antimicrobial resistance of biofilms.
authors.affiliation: Department of Clinical Microbiology, Fundación Jiménez Díaz, Madrid, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Ortíz-Pérez
authors.forename: Nieves
authors.initials: N
authors.lastname: Martín-de-Hijas
authors.forename: Noelia
authors.initials: N
authors.lastname: Alonso-Rodríguez
authors.forename: Diana
authors.initials: D
authors.lastname: Molina-Manso
authors.forename: Ricardo
authors.initials: R
authors.lastname: Fernández-Roblas
authors.forename: Jaime
authors.initials: J
authors.lastname: Esteban
mesh_terms: D000583:Amikacin / Q000493:pharmacokinetics* / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics* / Q000494:pharmacology; D058491:Bacterial Load; D018441:Biofilms / Q000187:drug effects*; D002939:Ciprofloxacin / Q000493:pharmacokinetics* / Q000494:pharmacology; D017291:Clarithromycin / Q000493:pharmacokinetics* / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial / Q000502:physiology*; D066298:In Vitro Techniques; D008826:Microbial Sensitivity Tests; D009161:Mycobacterium / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D009170:Nontuberculous Mycobacteria / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D013045:Species Specificity
chemical_list: D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D000583:Amikacin; D017291:Clarithromycin