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Comparative epidemiology of CTX-M-14 and CTX-M-15 producing Escherichia coli: Association with distinct demographic groups in the community in New Zealand


Extended spectrum beta-lactamase producing E. coli (ESBL-EC) are an emerging public health issue. In New Zealand (NZ), bla CTX-M-14 and bla CTX-M-15 are the most common ESBL genes. Although many studies describe risk factors for ESBL-EC, few describe risk factors for specific ESBL genes. Between January 2006 and December 2007, we characterized 108 consecutive, non-duplicate isolates of ESBL-EC at the Auckland Hospital laboratory. Demographic and clinical data were recorded. Of the 108, 54.6% (59) were CTX-M-15-EC, 26.9% (29) were CTX-M-14-EC and 12.09% were CTX-M-9 (13). The remaining seven isolates carried CTX-M-3 (3; 2.7%), CTX-M-65 (2; 1.8%), CTX-M-27 (1; 0.9%) and CTX-M-57 (1; 0.9%). CTX-M-15-EC were more likely than CTX-M-14-EC to be fluoroquinolone-resistant (86.4% versus 32.4%; p = 0.006) and to be non-susceptible to amoxicillin-clavulanate (84.7% versus 41.4%; p = 0.0001). Patients with CTX-M-15-EC were more likely to be of Indian ethnicity (34.5% versus 0%; p = 0.0012) and to have travelled recently (31.6% versus 4%; p = 0.0088). Patients with CTX-M-14-EC were more likely to have Chinese or South-East Asian ethnicity (48.1% versus 5.2%; p < 0.0001) and to have no history of either travel or prior hospital admission (44% versus 8.9%; p = 0.0006). These data imply that CTX-M-15 and CTX-M-14 producing E. coli are associated with distinct demographic subgroups in NZ.

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