Characteristics of extended-spectrum β-lactamase–producing Escherichia coli isolated from fecal samples of piglets with diarrhea in central and southern Taiwan in 2015

BACKGROUND The production of extended-spectrum β-lactamases (ESBLs) confer resistance to the commonly used beta-lactam antimicrobials and ESBL-producing bacteria render treatment difficulty in human and veterinary medicine. ESBL-producing bacteria have emerged in livestock in recent years, which may raise concerns regarding possible transfer of such bacteria through the food chain. The swine industry is important in Taiwan, but investigations regarding the status of ESBL in swine are limited. RESULTS We collected 275 fecal swab samples from piglets with diarrhea in 16 swine farms located in central and southern Taiwan from January to December 2015 and screened them for ESBL-producing Escherichia coli. ESBL producers were confirmed phenotypically by combination disc test and genotypically by polymerase chain reaction and DNA sequencing. The occurrence rate of ESBL-producing E. coli was 19.7% (54 of 275), and all were obtained in swine farms located in southern Taiwan. bla CTX-M-1-group and bla CTX-M-9-group were the two bla CTX-M groups found. bla CTX-M-55 (34 of 54; 63.0%) and bla CTX-M-15 (16 of 54; 29.6%), which belong to the bla CTX-M-1-group, were the two major bla gene types, whereas bla CTX-M-65 was the only type found in the bla CTX-M-9 group. Twenty-seven strains contained bla TEM-1, and the other 27 strains contained bla TEM-116. One strain found in Pingtung harbored three bla genes: bla TEM-116, bla CTX-M-55, and bla CTX-M-65. ESBL-producing E. coli exhibited a multidrug-resistant phenotype, and multilocus sequence typing revealed that the ST10 clonal complexes, including ST10, 167, 44, and 617 accounted for 35% (19 of 54) of these strains. CONCLUSIONS ESBL-producing E. coli from piglets with diarrhea were isolated from swine farms located in southern Taiwan. The most commonly detected bla were bla CTX-M-15 and bla CTX-M-55. The ST10 clonal complexes comprised most of our ESBL-producing E. coli strains. Fecal shedding from swine may contaminate the environment, resulting in public health concerns; thus, continued surveillance of ESBL is essential in swine and in other food animals.