Community emergence of CTX-M type extended-spectrum β-lactamases among urinary Escherichia coli from women

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Abstract
To conduct a territory-wide study of extended-spectrum β-lactamases (ESBLs) among community isolates of urinary Escherichia coli from women in Hong Kong. Up to 50 consecutive single-patient E. coli isolates, collected from 13 laboratories in 2004, were studied. The ESBLs were characterized by PCR sequencing using specific primers. The epidemiological relationship of the isolates was studied by PFGE and phylogenetic group PCRs. Forty-two ESBL producers were found among 600 consecutive isolates tested. The ESBL prevalence was 7.3% (15/205) for women aged 18–35 years, 5% (11/219) for women aged 36–50 years, 6.3% (4/63) for women aged 51–64 years and 10.6% (12/113) for women aged ≥65 years (P = 0.3). The ESBL-producing isolates were often multidrug-resistant and CTX-M-14 was found in 37 isolates, CTX-M-15 in 3 isolates and CTX-M-3 in 2 isolates. PFGE revealed no significant clusters among the ESBL producers. Overall, CTX-M-14 producers were significantly more likely to belong to group D than non-ESBL producers [18/37 (48.6%) versus 13/57 (22.8%), P = 0.009]. However, 7 of 13 (53.8%) CTX-M-14 producers from women aged 18–35 years represented phylogenetic group B2, compared with 7 of 24 (29.2%) for women of all other ages (P = 0.1). The study documented the community emergence of CTX-M as the predominant ESBL type among urinary isolates from women. The spread of CTX-M enzymes among isolates from young women is concerning and deserves close monitoring.