Epidemiologia molecolare di isolati clinici di P. aeruginosa MDR produttori di metallo-ß-lattamasi di tipo VIM-1 in una struttura di neuroriabilitazione

The VIM- and IMP-type metallo-ß-lactamases (MBLs) are clinically relevant emerging resistance determinants in Gram-negative nosocomial pathogens. To date, MBLs have been reported in acute care hospitals, but their epidemiology in Rehabilitation Facilities (RF) - the largest reservoirs of patients colonized by multidrug-resistant isolates - is largely unknown. This study is aimed to investigate MBL production in Pseudomonas aeruginosa isolates from “Fondazione S. Maugeri” Hospital an RF located in Pavia. 59 non replicate P. aeruginosa strains were isolated between July 2003 - March 2004, from patients incoming from different Italian hospitals. 18/59 resulted resistant to carbapenems. Phenotypic detection of the MBL producers was performed using the E-test and the EPI microdilution method. Molecular methods were used to investigate the MBL determinants and their genetic context.The clonal relatedness of the isolates were studied by PFGE. 12/18 carbapenem-resistant isolates were found to produce a VIM-type MBL. 7/12 were clonally related suggesting a clonal spread, while the 5 others, unrelated to the epidemic profile A, were simultaneously present in the same RF. Preventive and control measures including established microbiological protocols should be applied to detect the MBL producers and to contrast the diffusion of carbapenem-resistant P. aeruginosa in RF.