CHARACTERIZATION OF DUAL-SPECIES BIOFILMS DEVELOPED BY MICROORGANISMS INVOLVED IN POLYMICROBIAL CATHETER-ASSOCIATED URINARY TRACT INFECTIONS

MATEYCA, CELESTE; IELPI, LUIS; GALVAN, ESTELA M.

Cordoba

Congreso; XI Congreso Argentino de Microbiología General SAMIGE; 2015

Urinary catheterization is frequent in hospitals and long term care facilities. Bacteriuria associated with prolonged catheterization is polymicrobial. Establishment of biofilms constitutes a bacterial strategy for persistence on catheter surfaces. We aim to study whether microbial community interactions in dual-species biofilms developed by uropathogens could be beneficial or detrimental to the species involved.First, we performed a retrospective study at a public hospital in CABA to assess the local epidemiology of pathogens involved in catheter-associated polymicrobial bacteriuria. The more prevalent associations found were Klebsiella pneumoniae-Escherichia coli (Kp-Ec), E. coli-Enterococcus faecalis (Ec-Ef), K. pneumoniae-E. faecalis (Kp-Ef), and K. pneumoniae-Proteus mirabilis (Kp-Pm). Next, we studied the ability of these co-isolated species to grow as single- and dual-species biofilms, as well as planctonically, in artificial urine medium (AUM). Biofilms were formed on a siliconized surface allowing bacteria to attach for 3 h, and then replacing AUM every day. At different times, biofilms were disrupted mechanically and colony forming units (cfu) were assessed by plating on selective antibiotics. All species attached to the surface (5-30 cfu/cm2) and developed single-species biofilms, whose cell number increased over time and was maintained for 7 days. A 1000-fold increment in cell number was reached by both K. pneumoniae and E. coli biofilms, whereas the maximal increase in cell number reached by E. faecalis and P. mirabilis biofilms was 10-fold. The association Kp-Ec did not affect biofilm growth by K. pneumoniae but resulted in E. coli being outnumbered by K. pneumoniae after 72 h. In Ec-Ef dual-cultures, E. coli ability to form a biofilm was not altered, however, a 10-fold decrease in E. faecalis adherence to the surface, and a subsequent delay on biofilm development, was observed. Regarding Kp-Ef, characteristics of biofilm formation were identical to single-species biofilms. Planktonic growth of E. coli, E. faecalis, and K. pneumoniae in dual-species cultures were similar than single-species cultures. The Kp-Pm combination resulted in the impairment of K. pneumoniae, but not P. mirabilis, to attach to the surface and develop a biofilm. However, P. mirabilis behavior was similar in dual- and single-species biofilms. Kp-Pm liquid cultures showed a negative effect on K. pneumoniae growth and viability.Our findings evidenced a variety of effects occurring after two bacterial species being together into a biofilm. Establishment of Kp-Ec biofilms resulted in a detrimental effect over E. coli, while interactions in Ec-Ef co-cultures diminished the adhesion to the surface of E. faecalis. In addition, Kp-Pm interactions impaired K. pneumoniae biofilm. The results suggest that species behavior in dual-species biofilm depends on the identity of the two partners involved.