Biofilm formation by multidrug resistant Enterobacteriaceae strains isolated from solid organ transplant recipients

Solid organ transplant (SOT) recipients are especially at risk of developing infections by multidrug resistant bacteria (MDR). In this study, the biofilm-forming capability of 209 MDR strains (Escherichia coli n = 106, Klebsiella pneumoniae n = 78, and Enterobacter spp. n = 25) isolated from rectal swabs in the first 48 hours before or after kidney (93 patients), liver (60 patients) or kidney/pancreas transplants (5 patients) were evaluated by using a microplate assay. Thirty-nine strains were isolated before transplant and 170 strains were isolated post-transplant. Overall, 16% of E. coli strains, 73% of K. pneumoniae strains and 4% Enterobacter strains showed moderate or strong biofilm production. Nine strains isolated from infection sites after transplantation were responsible of infections in the first month. Of these, 4 K. pneumoniae, 1 E. coli and 1 Enterobacter spp. strains isolated pre-transplant or post-transplant as colonizers caused infections in the post-transplant period. Our results suggest that in vitro biofilm formation could be an important factor for adhesion to intestine and colonization in MDR K. pneumoniae strains in SOT recipients, but this factor appears to be less important for MDR E. coli and Enterobacter spp. Acknowledgements: The authors thank Dr. Fidel Madrazo (Electron Microscopy Unit, Technology Support Services, IDIVAL) for helping with confocal microscopy. This research was supported by ‘Plan Nacional de I + D + i and Instituto de Salud Carlos III (Fondo de Investigaciones Sanitarias PI 13/01191 to MCF and PI 16/01103 to JRV), Subdirección General de Redes y Centros de Investigación Cooperativa, Spanish Ministry of Economy and Competitiveness, Spanish Network for Research in Infectious Diseases (REIPI RD12/0015) and (REIPI RD16/0016) co-financed by the European Development Regional Fund “A way to achieve Europe” ERDF.