First report of CTX-M producing Escherichia coli, including the new ST2526, isolated from beef cattle and sheep in Portugal

The prevalence of extended-spectrum β-lactamase-containing Escherichia coli isolates was studied in beef cattle and sheep at slaughter in Portugal. CTX-M-producing E. coli isolates were detected in 7% of the 127 fecal samples. The β-lactamase genes detected were as following: CTX-M-32 (n = 4), TEM-1 + CTX-M-1 (n = 3) and CTX-M-1 (n = 2). All CTX-M-containing isolates exhibit a multiresistant phenotype. MLST analysis revealed four different STs under 2 ST complexes (STC10 and STC155) and we detected a novel allelic profile representing a new ST, registered in the database as ST2526. Five of the CTX-M-containing isolates were classified in the B1 phylogroup and 4 isolates in the A phylogroup. Eight isolates harbored at least one of the virulence factors studied. Detection of CTX-M-producers E. coli in beef cattle and sheep raises important questions as they can represent a potential risk factor to public health.