A binational cohort study of intestinal colonization with extended-spectrum β-lactamase-producing Proteus mirabilis in patients admitted to rehabilitation centres.

The aims of our study were to analyse the risk factors for colonization by Extended-spectrum β-lactamases (ESBL)-producing Proteus mirabilis (ESBL-PM) in rehabilitation patients and to characterize the molecular features of these strains. The study was conducted in two rehabilitation centres located in Rome, Italy (Fondazione Santa Lucia IRCCS (FSL)), and Tel-Aviv, Israel (Tel-Aviv Sourasky Medical Center (TASMC)). Carriage of ESBL-PM was surveyed by rectal swabs. Strain typing was performed by pulsed-field gel electrophoresis (PFGE). Identification of ESBL genes was done by PCR and sequencing. Patients admitted to the same institutions without ESBL carriage were included as controls. The study group included 70 and 41 patients from FSL and TASMC, respectively. In FSL, the multivariate analysis identified severe acute brain injury (OR = 15, 95% CI = 3.2-69.5, p 0.001), decubitus ulcer (OR = 3.5, 95% CI = 1.2-9.8, p 0.018) and recent treatment with quinolones (OR = 5.7, 95% CI = 1.07-30.1, p 0.042) as independent risk factors. ESBL-PM carriers stayed longer in the hospital on average and were less likely to be discharged home. No significant risk factor was identified in TASMC. There were no similarities in PFGE types or ESBL genes between the ESBL-PM isolates from the two institutions. In both hospitals, a variety of PFGE types existed but a single ESBL type predominated, namely TEM-92 in FSL (n = 64/70; 91%) and CTX-M-2 in TASMC (n = 37/41; 90%). A new TEM ESBL variant, TEM-177 was identified in FSL. The clonal diversity and the predominance of a single ESBL type suggested that horizontal gene transfer played an important role in dissemination of resistance. The development of a population analysis tool that would allow tracing deeper genetic relationships is required.