Acquired AmpC type beta-lactamases: an emerging problem in Italian long-term care and rehabilitation facilities.

We report the multiple detection of Proteus mirabilis isolates, from 4 different long-term care and rehabilitation facilities (LTCRFs) of Northern Italy, resistant to expanded-spectrum cephalosporins and cephamycins and producing an acquired ampC-like beta-lactamase, named CMY-16. Genotyping by PFGE showed that isolates were clonally related to each other, although not identical. In all isolates the bla(CMY16) gene was not transferable by conjugation and was found to be carried on the chromosome. These results revealed multifocal spreading of a CMY-16 producing P. mirabilis clone in Northern Italy and emphasize the emergence of similar acquired resistance determinants in the LTCRFs setting.