title: Prevalence of Antimicrobial Resistance and Transfer of Tetracycline Resistance Genes in Escherichia coli Isolates from Beef Cattle.
abstract: The aim of this study was to investigate the prevalence and transferability of resistance in tetracycline-resistant Escherichia coli isolates recovered from beef cattle in South Korea. A total of 155 E. coli isolates were collected from feces in South Korea, and 146 were confirmed to be resistant to tetracycline. The tetracycline resistance gene tet(A) (46.5%) was the most prevalent, followed by tet(B) (45.1%) and tet(C) (5.8%). Strains carrying tet(A) plus tet(B) and tet(B) plus tet(C) were detected in two isolates each. In terms of phylogenetic grouping, 101 (65.2%) isolates were classified as phylogenetic group B1, followed in decreasing order by D (17.4%), A (14.2%), and B2 (3.2%). Ninety-one (62.3%) isolates were determined to be multidrug resistant by the disk diffusion method. MIC testing using the principal tetracyclines, namely, tetracycline, chlortetracycline, oxytetracycline, doxycycline, and minocycline, revealed that isolates carrying tet(B) had higher MIC values than isolates carrying tet(A). Conjugation assays showed that 121 (82.9%) isolates could transfer a tetracycline resistance gene to a recipient via the IncFIB replicon (65.1%). This study suggests that the high prevalence of tetracycline-resistant E. coli isolates in beef cattle is due to the transferability of tetracycline resistance genes between E. coli populations which have survived the selective pressure caused by the use of antimicrobial agents.
authors.affiliation: Department of Infectious Diseases, College of Veterinary Medicine, Seoul National University, Seoul, Republic of Korea.
authors.forename: Seung Won
authors.initials: SW
authors.lastname: Shin
authors.affiliation: Department of Infectious Diseases, College of Veterinary Medicine, Seoul National University, Seoul, Republic of Korea.
authors.forename: Min Kyoung
authors.initials: MK
authors.lastname: Shin
authors.affiliation: Department of Infectious Diseases, College of Veterinary Medicine, Seoul National University, Seoul, Republic of Korea.
authors.forename: Myunghwan
authors.initials: M
authors.lastname: Jung
authors.affiliation: Department of Infectious Diseases, College of Veterinary Medicine, Seoul National University, Seoul, Republic of Korea.
authors.forename: Kuastros Mekonnen
authors.initials: KM
authors.lastname: Belaynehe
authors.affiliation: Department of Infectious Diseases, College of Veterinary Medicine, Seoul National University, Seoul, Republic of Korea Institute of Green Bio Science and Technology, Seoul National University, Pyeungchang, Republic of Korea yoohs@snu.ac.kr.
authors.forename: Han Sang
authors.initials: HS
authors.lastname: Yoo
mesh_terms: D000818:Animals; D002417:Cattle; D003227:Conjugation, Genetic; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D005243:Feces / Q000382:microbiology*; D022761:Gene Transfer, Horizontal; D005798:Genes, Bacterial; D005838:Genotype; D008826:Microbial Sensitivity Tests; D058889:Molecular Typing; D015995:Prevalence; D000069466:Red Meat; D056910:Republic of Korea; D013753:Tetracycline Resistance