title: Macrolides decrease the minimal inhibitory concentration of anti-pseudomonal agents against Pseudomonas aeruginosa from cystic fibrosis patients in biofilm.
abstract: BACKGROUND
  Biofilm production is an important mechanism for bacterial survival and its association with antimicrobial resistance represents a challenge for the patient treatment. In this study we evaluated the in vitro action of macrolides in combination with anti-pseudomonal agents on biofilm-grown Pseudomonas aeruginosa recovered from cystic fibrosis (CF) patients.
  
  
  RESULTS
  A total of 64 isolates were analysed. The biofilm inhibitory concentration (BIC) results were consistently higher than those obtained by the conventional method, minimal inhibitory concentration, (MIC) for most anti-pseudomonal agents tested (ceftazidime: P = 0.001, tobramycin: P = 0.001, imipenem: P < 0.001, meropenem: P = 0.005). When macrolides were associated with the anti-pseudomonal agents, the BIC values were reduced significantly for ceftazidime (P < 0.001) and tobramycin (P < 0.001), regardless the concentration of macrolides. Strong inhibitory quotient was observed when azithromycin at 8 mg/L was associated with all anti-pseudomonal agents tested in biofilm conditions.
  
  
  CONCLUSIONS
  P. aeruginosa from CF patients within biofilms are highly resistant to antibiotics but macrolides proved to augment the in vitro activity of anti-pseudomonal agents.
authors.affiliation: Unidade de Microbiologia, Serviço de Patologia Clínica, Hospital de Clínicasde Porto Alegre, Porto Alegre, Brazil. albarth@hcpa.ufrgs.br
authors.forename: Larissa
authors.initials: L
authors.lastname: Lutz
authors.forename: Dariane Castro
authors.initials: DC
authors.lastname: Pereira
authors.forename: Rodrigo Minuto
authors.initials: RM
authors.lastname: Paiva
authors.forename: Alexandre Prehn
authors.initials: AP
authors.lastname: Zavascki
authors.forename: Afonso Luis
authors.initials: AL
authors.lastname: Barth
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D002648:Child; D002675:Child, Preschool; D003550:Cystic Fibrosis / Q000150:complications; D004357:Drug Synergism; D005260:Female; D006801:Humans; D018942:Macrolides / Q000494:pharmacology*; D008297:Male; D008826:Microbial Sensitivity Tests; D011552:Pseudomonas Infections / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000302:isolation & purification / Q000502:physiology*; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides