Antimicrobial susceptibility and characterization of extended-spectrum β-lactamases in Escherichia coli isolated from bovine mastitic milk in South Korea from 2012 to 2015.
In this study, we aimed to assess trends in antimicrobial resistance and to investigate the characteristics of extended-spectrum β-lactamase (ESBL)-producing isolates from bovine mastitic milk from 2012 to 2015. A total of 374 Escherichia coli isolates were analyzed (154 in 2012, 113 in 2013, 76 in 2014, and 31 in 2015). No consistent trends in antimicrobial resistance of E. coli isolates occurred during the 4-yr period. The most frequently observed resistance was tetracycline (23.3%), followed by streptomycin (17.1%), ampicillin (16.6%), neomycin (11.8%), and trimethoprim/sulfamethoxazole (11.2%). Multidrug resistance was observed in 15.5% of isolates. Among these isolates, 15 (4.0%) carried one or more blaCTX-Mand AmpC ESBL genes from 11 different farms, including blaCTX-M-15at 4 farms, blaCTX-M-3at 2 farms, blaCTX-M-1at 3 farms, and blaCMY-2at 3 farms. This study is the first report of blaCTX-M-3-producing E. coli in dairy milk. Transfer of ESBL was observed in 3 blaCTX-M-3-producing isolates, 1 blaCTX-M-1-producing isolate, and all 3 blaCMY-2-producing isolates. Almost all blaCTX-M-15and blaCTX-M-1genes possessed an insertion sequence, ISECP1, upstream of the blaCTX-Mgene. Identical pulsed-field gel electrophoresis profiles were also observed in blaCTX-M-producing E. coli from the same farm. These results suggested that ESBL might spread by both clonal and horizontal spread in dairy farms in South Korea. Although no significant changes occurred in the antimicrobial resistance of E. coli during the 4-yr study period, the resistance rates and presence of ESBL were high compared with those in other countries. Thus, these findings suggest the importance of control measures for E. coli, particularly ESBL-producing bacteria, on dairy farms to reduce treatment failure and transmission to humans.
Korea Zoonosis Research Institute, Chonbuk National University, 820-120 Hana-ro, Iksan, Jeonbuk 54531, Republic of Korea.
Dong-Seob
DS
Tark
Bacterial Disease Division, Animal and Plant Quarantine Agency, 177 Hyeksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, Republic of Korea.
Dong Chan
DC
Moon
Bacterial Disease Division, Animal and Plant Quarantine Agency, 177 Hyeksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, Republic of Korea.
Hee Young
HY
Kang
Bacterial Disease Division, Animal and Plant Quarantine Agency, 177 Hyeksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, Republic of Korea.
Su-Ran
SR
Kim
Bacterial Disease Division, Animal and Plant Quarantine Agency, 177 Hyeksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, Republic of Korea.
Hyang-Mi
HM
Nam
Bacterial Disease Division, Animal and Plant Quarantine Agency, 177 Hyeksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, Republic of Korea.
Hee-Soo
HS
Lee
Bacterial Disease Division, Animal and Plant Quarantine Agency, 177 Hyeksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, Republic of Korea.
Suk-Chan
SC
Jung
Bacterial Disease Division, Animal and Plant Quarantine Agency, 177 Hyeksin 8-ro, Gimcheon-si, Gyeongsangbuk-do 39660, Republic of Korea. Electronic address: imsk0049@korea.kr.
Suk-Kyung
SK
Lim
D000818:Animals; D000890:Anti-Infective Agents / Q000627:therapeutic use; D002417:Cattle; D004926:Escherichia coli / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000662:veterinary; D006801:Humans; D008892:Milk / Q000382:microbiology; D010957:Plasmids; D001618:beta-Lactamases
D000890:Anti-Infective Agents; D001618:beta-Lactamases
Escherichia coli; bovine mastitic milk; extended-spectrum β-lactamase; multidrug resistance