Silicone colonization by non-Candida albicans Candida species in the presence of urine

Abstract

Urinary tract infections (UTIs) are the most common nosocomial infections and 80 % are related to the use of urinary catheters. Furthermore,Candidaspecies are responsible for around 15 % of UTIs and an increasing involvement of non-Candida albicans Candida(NCAC) species (e.g.Candida glabrata,Candida tropicalisandCandida parapsilosis) has been recognized. Given the fact that silicone is frequently used in the manufacture of urinary catheters, the aim of this work was to compare both the adhesion and biofilm formation on silicone of different urinary clinical isolates of NCAC species (i.e.C. glabrata,C. tropicalisandC. parapsilosis) in the presence of urine. Several clinical isolates of NCAC species recovered from patients with UTIs, together with reference strains of each species, were examined. Adhesion and biofilm formation were performed in artificial urine and the biofilm biomass was assessed by crystal violet staining. Hydrophobicity and surface charge of cells was determined by measuring contact angles and zeta potential, respectively. The number of viable cells in biofilms was determined by enumeration of c.f.u. after appropriate culture. The biofilm structure was also examined by confocal laser scanning microscopy (CLSM). The results showed that all isolates adhered to silicone in a species- and strain-dependent manner withC. parapsilosisshowing the lowest andC. glabratathe highest levels of adhesion. However, these differences in adhesion abilities cannot be correlated with surface properties since all strains examined were hydrophilic and exhibited a similar zeta potential. Despite a higher number of cultivable cells being recovered after 72 h of incubation, stronger biofilm formation was not observed and CLSM showed an absence of extracellular polymeric material for all isolates examined. In summary, this work demonstrated that all tested NCAC species were able to adhere to and survive on silicone in the presence of urine. Furthermore,C. glabratastrains presented higher colonization abilities thanC. tropicalisandC. parapsilosisstrains, a fact that might explain the larger role ofC. glabratacolonization and disseminated infections in hospitalized and catheterized patients.