Multidrug-Resistant Bacteria in Southeastern Austria

To the Editor: In many parts of the world, the proportions of methicil-lin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant en-terococci, and extended-spectrum β-lactamase (ESBL)–producing organisms in the family Enterobacteriaceae have increased remarkably during recent years (1). However, proportions of antimicrobial drug resistance vary substantially at national and regional levels. We describe antimicrobial drug resistance data for hospitalized patients and outpatients in southeast Austria. A total of 690,967 clinical samples were collected from hospitalized patients and outpatients and analyzed at the microbiology laboratory of the Medical University of Graz during 1997–2006. Selected for resistance surveillance were nonduplicate isolates of S. aureus, Enterococcus fae-cium, E. faecalis, Escherichia coli, and Klebsiella spp. Antibiotic suscep-tibilities were determined by using disk diffusion and the VITEK2 system (bioMérieux, Marcy l'Etoile, France) with specifi c susceptibility test cards. Etest (AB Biodisk, Solna, Sweden) was used to confi rm results. Test results were interpreted according to the recommendations of the Clinical and Laboratory Standards Institute (2). During the study period, the proportion of patients with MRSA remained stable (2.5%–4.9%) (Figure, panel A). The prevalence of MRSA among invasive S. aureus isolates ranges between 0.5% and 44.4% in European countries and has increased in recent years (3). We found MRSA predominantly in samples from hospitalized patients (median 72.1%); however, the incidence of community acquired MRSA increased slightly during recent years, similar to that of other central European countries (4). Vancomycin resistance was not noted during the study period; however, 4 vancomycin-intermediate MRSA isolates were noted in 2004, 2005, and 2006, in concordance with the sporadic occurrence of MRSA with intermediate susceptibility to glycopeptides recently reported for other European countries (3). The percentage of patients with vancomycin-resistant E. faecium and E. faecalis was low (median 0.4%) (Figure, panel A). In total, 10 E. fae-cium and 4 E. faecalis isolates with resistance to vancomycin were reported; most were from hospitalized patients. As in most European countries, human infections due to glycopeptide-resistant enterococci remain rare in Austria, although a high proportion of glycopeptide-resistant E. faecium was reported recently from animals used in food production (5). Among E. coli isolates, no ESBL producers were noted in 1997. From 1998 through 2002, proportions of ESBL-producing E. coli were 0.06%– 0.13%, which corresponds to 3–6 isolates per year. A subsequent increase of ESBL-producing E. coli isolates was noted, from 19 (0.3%) in 2003 to 148 (2.4%) in 2006 (Figure, panel B). Most (67%) ESBL-producing isolates found during …