Colonisation and infection due to Enterobacteriaceae producing plasmid-mediated AmpC β-lactamases

Objectives: To investigate theepidemiology and clinical features of infections caused by Enterobacteria producing plasmid-mediated AmpC beta-lactamases (pAmpC), which are emerging as a cause of resistance to extended-spectrum cephalosporins. Methods: A prospective multicentre cohort of patients with infection/colonisation due to pAmpC-producing Enterobacteriaceae was performed in 7 Spanish hospitals from February throughout July 2009. pAmpCs were characterised by PCR and sequencing. Results: 140 patients were included; organisms isolated were Escherichia coli (n=100), Proteus mirabilis (n=20), Klebsiella pneumoniae (n=17), and others (n=3). Overall, 90% had a chronic underlying condition. The acquisition was nosocomial in 43%, healthcare-associated in 41% (14% of those were nursing home residents), and community in 16%. Only 5% of patients had no predisposing feature for infection with multidrug-resistant bacteria. Nineteen percent of patients were bacteraemic. Inappropriate empirical therapy was administered to 81% of bacteraemic patients, who had a crude mortality rate of 48%. The most frequent enzyme was CMY-2 (70%, predominantly in E. coli and P. mirabilis) followed by DHA-1 (19%, predominantly in K. pneumoniae). Conclusion: pAmpC-producing Enterobacteriaceae caused nosocomial, healthcare-associated and community infections mainly inpredisposed patients. Invasive infections were associated with high mortality which might be partly related to inappropriate empirical therapy. (C) 2011 The British Infection Association. Published by Elsevier Ltd. All rights reserved.