Extended-spectrum cephalosporin-resistant Escherichia coli in community, specialized outpatient clinic and hospital settings in Switzerland

Objectives: Resistance to extended-spectrum cephalosporins (ESCs) in Escherichia coli can be due to the production of ESBLs, plasmid-mediated AmpCs (pAmpCs) or chromosomal AmpCs (cAmpCs). Information regarding type and prevalence of beta-lactamases, clonal relations and plasmids associated with the bla genes for ESC-R E. coli (ESC-R-Ec) detected in Switzerland is lacking. Moreover, data focusing on patients referred to the specialized outpatient clinics (SOCs) are needed. Methods: We analysed 611 unique E. coli isolated during September-December 2011. ESC-R-Ec were studied with microarrays, PCR/DNA sequencing for bla(ESBLs), bla(pAmpCs), promoter region of bla(cAmpC), IS elements, plasmid incompatibility group, and also implementing transformation, aIEF, rep-PCR and MLST. Results: The highest resistance rates were observed in the SOCs, whereas those in the hospital and community were lower (e. g. quinolone resistance of 22.6%, 17.2% and 9.0%, respectively; P = 0.003 for SOCs versus community). The prevalence of ESC-R-Ec in the three settings was 5.3% (n = 11), 7.8% (n = 22) and 5.7% (n = 7), respectively. Thirty isolates produced CTX-M ESBLs (14 were CTX-M-15), 5 produced CMY-2 pAmpC and 5 hyper-expressed cAmpCs due to promoter mutations. Fourteen isolates were of sequence type 131 (ST131; 10 with CTX-M-15). bla(CTX-M) and bla(CMY-2) were associated with an intact or truncated ISEcp1 and were mainly carried by IncF, IncFII and IncI1plasmids. Conclusions: ST131 producing CTX-M-15 is the predominant clone. The prevalence of ESC-R-Ec (overall 6.5%) is low, but an unusual relatively high frequency of AmpC producers (25%) was noted. The presence of ESC-R-Ec in the SOCs and their potential ability to be exchanged between hospital and community should be taken into serious consideration.