title: ESBL-ProducingEscherichia colifrom Cows Suffering Mastitis in China Contain Clinical Class 1 Integrons with CTX-M Linked to ISCR1.
abstract: The prevalence of pathogenic multi-drug resistant (MDR) extended-spectrum β-lactamase (ESBL)-producingEscherichia coliis rapidly increasing, becoming a global concern. In a veterinary context, ESBL-producingE. coliare mostly reported in poultry and pigs. Here, we report on the prevalence and characterize ESBL-producingE. coliisolated from diverse dairy farms in China. Overall, 36 (23.53%) out of 153E. coliisolates from mastitic milk samples (n= 1252) were confirmed as ESBL-producers by double-disc synergy testing and PCR. Nucleotide analysis of PCR amplicons revealed thatblaCTX-Mwas the predominant ESBL gene detected in 28 (77.78%) isolates, withblaCTX-M-15being the major (78.57%) allele encoding for ESBLs. Also, 20 (55.56%) and 6 (16.67%) of the ESBL isolates were carryingblaTEMandblaSHVgenes, respectively, in singlet or in combination. The majority of these isolates belonged to phylo-group A (69.44%) and D (16.67%). Strikingly, all these isolates were found to be MDR showing high resistance to cephalosporins including the fourth generation cefepime and common non β-lactams. Additionally, class 1 integrons (intI1) were found in 30 (83.33%) isolates. Analysis of the class 1 integrons variable regions indicated that they were carrying up to five different gene cassettes conferring resistance to various drugs with a predominant combination ofdfrA17-aadA5genes in tandem, conferring resistance to aminoglycosides and trimethoprim. However, no ESBL encoding genes were found in the cassettes. Interestingly, 22 (66.11%) of the ESBL isolates were also carrying insertion sequence common region 1 (ISCR1) which was found to be associated with most of the CTX-M genes. Altogether, the current study reports on the high prevalence of ESBL-positiveE. coli, particularly CTX-M-15, carrying clinical class 1 integrons and ISCR1elements are likely indicative of their rapid and wider dissemination, posing threats to veterinary and public health. To the best of our knowledge, this is the first comprehensive study to report on the alarming high occurrence of ESBL-producingE. colifrom mastitic cows in China.
authors.affiliation: Department of Clinical Veterinary Medicine, College of Veterinary Medicine, China Agricultural University Beijing, China.
authors.forename: Tariq
authors.initials: T
authors.lastname: Ali
authors.affiliation: College of Veterinary Sciences and Animal Husbandry, Abdul Wali Khan University, Garden Campus Mardan, Pakistan.
authors.forename: Sadeeq
authors.initials: S
authors.lastname: Ur Rahman
authors.affiliation: Department of Clinical Veterinary Medicine, College of Veterinary Medicine, China Agricultural University Beijing, China.
authors.forename: Limei
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Clinical Veterinary Medicine, College of Veterinary Medicine, China Agricultural University Beijing, China.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Shahid
authors.affiliation: Department of Clinical Veterinary Medicine, College of Veterinary Medicine, China Agricultural University Beijing, China.
authors.forename: Shiyao
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Clinical Veterinary Medicine, College of Veterinary Medicine, China Agricultural University Beijing, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Liu
authors.affiliation: Department of Clinical Veterinary Medicine, College of Veterinary Medicine, China Agricultural University Beijing, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Gao
authors.affiliation: Department of Clinical Veterinary Medicine, College of Veterinary Medicine, China Agricultural University Beijing, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Han
keywords: CTX-M-15; E. coli; ESBLs; bovine mastitis; gene cassettes; integrons