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.