title: In vitro activity of ciprofloxacin, moxifloxacin, vancomycin and erythromycin against planktonic and biofilm forms of Corynebacterium urealyticum.
abstract: OBJECTIVE
  To study the ability of Corynebacterium urealyticum to produce biofilms and to compare the in vitro activity of antimicrobials against planktonic and biofilm-associated organisms.
  
  
  METHODS
  Biofilm formation on polystyrene plates by three C. urealyticum strains was studied in artificial urine under static conditions. The bactericidal activities of ciprofloxacin, moxifloxacin, vancomycin and erythromycin were studied against biofilm-associated organisms, and the results were compared with those obtained against planktonic organisms. Persister biofilm-associated organisms of each strain exposed to antibiotics were retested to determine the MIC of the same antibiotic.
  
  
  RESULTS
  The three strains tested consistently produced biofilms. Planktonic organisms was susceptible to ciprofloxacin, moxifloxacin and vancomycin, and their MBC values were two to eight times higher than their corresponding MICs. Bactericidal effect on biofilm-associated organisms required very high antibiotic concentrations; the minimum biofilm bactericidal concentrations for ciprofloxacin, moxifloxacin and vancomycin ranged from 128 to > or =1024 times their respective MBCs for planktonic organisms. Erythromycin was not bactericidal against either planktonic or biofilm-associated organisms for the single susceptible strain tested. Persister biofilm-associated organisms exposed to erythromycin increased their MIC by a factor >8000, but no changes in susceptibility were observed with the other compounds.
  
  
  CONCLUSIONS
  This work demonstrates that C. urealyticum produces biofilms on polystyrene plates and biofilm-associated organisms are much less susceptible to the bactericidal effect of the antibiotics; and the exposure of C. urealyticum to erythromycin may favour resistance selection. Overall, these results may explain the difficulties for bacterial eradication in chronic infections caused by C. urealyticum.
authors.affiliation: Department of Medical Microbiology and Antimicrobial Chemotherapy, Fundación Jiménez Díaz, Madrid, Spain. fsoriano@fjd.es
authors.forename: Francisco
authors.initials: F
authors.lastname: Soriano
authors.forename: Lorena
authors.initials: L
authors.lastname: Huelves
authors.forename: Plinio
authors.initials: P
authors.lastname: Naves
authors.forename: Violeta
authors.initials: V
authors.lastname: Rodríguez-Cerrato
authors.forename: Gema
authors.initials: G
authors.lastname: del Prado
authors.forename: Vicente
authors.initials: V
authors.lastname: Ruiz
authors.forename: Carmen
authors.initials: C
authors.lastname: Ponte
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D003352:Corynebacterium / Q000187:drug effects* / Q000302:isolation & purification; D003354:Corynebacterium Infections / Q000382:microbiology; D004917:Erythromycin / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability; D011804:Quinolines / Q000494:pharmacology*; D014556:Urine / Q000382:microbiology; D014640:Vancomycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D011804:Quinolines; D004917:Erythromycin; D014640:Vancomycin