title: Differences in biofilm development and antibiotic susceptibility among clinical Ureaplasma urealyticum and Ureaplasma parvum isolates.
abstract: OBJECTIVE
  The aim of this work was to study the ability of clinical isolates of Ureaplasma spp. to form biofilms in vitro and to compare the antibiotic susceptibility of sessile cells and their planktonic counterparts.
  
  
  METHODS
  A total of nine Ureaplasma spp. isolates recovered from unrelated male patients diagnosed with urethritis or chronic prostatitis and two isolates isolated from the urine of two healthy volunteers were included. Ureaplasma species identification was performed by 16S rDNA gene amplification and sequencing. Conventional antibiotic susceptibility tests were carried out by the broth microdilution method. Biofilm susceptibility assays were performed following the method proposed by Moskowitz using 10C urea broth medium and confirming bacterial growth by colour shift of the medium. The chi(2) test was applied to analyse the statistical differences between the MIC and the minimal biofilm inhibitory concentration.
  
  
  RESULTS
  Isolates were identified as Ureaplasma urealyticum serovar 7 (five isolates), U. urealyticum serovar 13 (four isolates) and Ureaplasma parvum serovar 3 (two isolates). Biofilm formation was observed in 9 out of the 11 strains studied (82%); two isolates of U. urealyticum serovar 13 were non-biofilm formers. Global resistance percentages of planktonic cells compared with sessile cells were different for erythromycin (0% versus 44%, P = 0.02), telithromycin (22% versus 77%, P = 0.02), ciprofloxacin (66% versus 100%), levofloxacin (0% versus 33%) and tetracycline (0% versus 33%). All nine biofilm-forming strains were fully susceptible to clarithromycin in both planktonic and biofilm types of growth.
  
  
  CONCLUSIONS
  These results indicate that biofilm formation can protect mycoplasma cells from antibiotics and host defences, favouring their persistence in chronically infected or colonized patients while increasing resistance to antimicrobial agents. Therefore, the capacity to form biofilms by Ureaplasma spp. isolates should be considered when antibiotic treatments are required.
authors.affiliation: Servicio de Microbiología, Hospital Universitario Ramón y Cajal y CIBER en Epidemiología y Salud Pública, Ctra Colmenar Km 9.1, Madrid 28034, Spain.
authors.forename: María
authors.initials: M
authors.lastname: García-Castillo
authors.forename: María-Isabel
authors.initials: MI
authors.lastname: Morosini
authors.forename: María
authors.initials: M
authors.lastname: Gálvez
authors.forename: Fernando
authors.initials: F
authors.lastname: Baquero
authors.forename: Rosa
authors.initials: R
authors.lastname: del Campo
authors.forename: María-Antonia
authors.initials: MA
authors.lastname: Meseguer