Prevalence and diversity of extended-spectrum β-lactamases in faecal Escherichia coli isolates from healthy humans in Spain

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolates were detected in seven of 105 faecal samples from healthy humans, from two Spanish cities, during 2007. In these isolates, five ESBLs were detected, CTX-M-14 ( n  = 2), CTX-M-1 ( n  = 2), CTX-M-32 ( n  = 1), CTX-M-8 ( n  = 1) and TEM-52 ( n  = 1). Both bla _CTX-M-14a (surrounded by IS Ecp1 -IS 903 ) and bla _CTX-M-14b variants (included in an integron structure) were identified in this study. This is the first time that the bla _CTX-M-8 gene and ESBLs of the CTX-M-8 group have been found in Europe and Spain, respectively. Faecal E. coli of healthy humans therefore constitute a reservoir of bla _CTX-M genes with different surrounding genetic elements.