Molecular survey of -lactamases conferring resistance to newer generation -lactams in Enterobacteriaceae in Polish hospitals

Joanna Empel, Anna Baraniak, Elbieta Literacka, Agnieszka Mrówka, Janusz Fiett, Ewa Sadowy, Waleria Hryniewicz, Marek Gniadkowski^*, and The Beta-PL Study Group

National Medicines Institute, 00-725 Warsaw, Poland

^* To whom correspondence should be addressed. Email: gniadkow{at}cls.edu.pl.

	Abstract

The first national survey of resistance to newer generation -lactams in nosocomial populations of Enterobacteriaceae was performed in Poland. The study covered all non-repetitive enterobacterial isolates cultured from inpatients in 13 regional secondary-care hospitals from November 2003 to January 2004. Among 2,388 isolates, the predominant species was Escherichia coli (59.6%), followed by Proteus mirabilis (14.5%), and Klebsiella spp. (8.5%). The frequency of extended-spectrum -lactamases (ESBLs) was very high, with 11.1% among all isolates and 40.4% in Klebsiella pneumoniae, the latter value much exceeding that for E. coli (2.5%). The contribution of outbreak isolates was significant, resulting for example in a particularly high rate of ESBLs in Serratia marcescens (70.8%). The pool of ESBL types was totally dominated (81.7%) by CTX-M-like -lactamases, CTX-M-3 (80.6%) and CTX-M-15, followed by SHV types (17.5%; SHV-2, SHV-5, SHV-12), and sporadic TEM-like enzymes (0.7%; TEM-19, TEM-48). Acquired AmpC-type cephalosporinases were observed exclusively in P. mirabilis, accounting for 20.5% of its isolates (compared with 11.5% of ESBL producers in that species). All these enzymes were of the Citrobacter freundii origin (CMY-12, CMY-15, and a novel variant CMY-38). Four isolates of E. coli, K. pneumoniae and P. mirabilis produced class A inhibitor-resistant -lactamases (TEM-30, TEM-32, TEM-37 and SHV-49), being the first isolates of that kind identified in Poland. The survey documented both specific and more global characteristics of the epidemiology of the -lactamase-mediated resistance in enterobacteria in Polish hospitals, and demonstrated that the ESBL frequency has reached the alarming level.