Interrelationship between tetracycline resistance determinants, phylogenetic group affiliation and carriage of class 1 integrons in commensal Escherichia coli isolates from cattle farms

Abstract

BackgroundCarriage of antibiotic-resistant foodborne pathogens by food production animals is one of many contributors to treatment failure in health care settings, and it necessitates an integrated approach to investigate the carriage of resistant pathogens harboring integrons in food-producing animals.MethodsEscherichia coli isolates with reduced susceptibility to tetracycline antibiotics (n = 92) were tested for associations between carriage of class1 integrons, phylogenetic group affiliation and tetracycline resistance determinants using the MIC method, PFGE analysis, PCR and sequencing.ResultsPhylogroups B1 and A were the most common (58.7 and 19.6%, respectively), followed by groups D (20.7%) and B2 (1.1%). All isolates carried at least one of the tet genes examined. In addition, 88 (95.7%) of all tetracycline-resistant isolates carried tet(A) or tet(B), while 47 (51.1%) and 41 (44.6%) harbored only tet(A) or tet(B), respectively. Likewise, isolates harboring these genes had a higher chance (P < 0.05) of carrying class 1 integrons. Of the tested isolates, 38 (41.3%) carried the intI1 gene. Classical integrons with complete genes (sul1 and qacE∆1) at the 3′-CS were recognized in 27 isolates. PCR screening and subsequent sequencing demonstrated that 84.2% (32/38) of the intI1-positive isolates harbored resistance gene cassettes. Overall, seven gene cassettes were identified, either solely or combined with another gene cassette. The most common gene was aadA1 (10 isolates), followed by a combination of aadA1-dfrA1 (seven isolates), aadA1-dfrA12 (six isolates) and aadA1-aadA2-dfrA12 (three isolates). Genetic typing using PFGE showed minimum clonal relatedness with 28 different clusters and 12–25 discernible DNA fragments.ConclusionsThis study brings new insight into the relationships between the presence of integrons, phylogenetic group association and characteristics of tetracycline antibiotic resistance determinants in commensal E. coli strains.

A One Health Comparative Assessment of Antimicrobial Resistance in Generic and Extended-Spectrum Cephalosporin-Resistant Escherichia coli from Beef Production, Sewage and Clinical Settings

“…Consequently, it is likely that the high MDRs reflect long-term exposure of bacteria to specific antimicrobials [ 87 ]. Long-term tetracycline use confers resistance to other antimicrobial agents via co-selection, as tet genes and other resistance genes often share common integrons, plasmids or transposons [ 65 , 90 ].…”

Targeting Plasmids to Limit Acquisition and Transmission of Antimicrobial Resistance

“…Integrons are divided into several classes (class 1, class 2, and class 3) depending on the amino acid sequence of the IntI enzyme. Class 1 integrons, which are typically associated with plasmids, are most commonly encountered in clinical isolates from hospitals and elderly care facilities, but have also been found in food production chain isolates (e.g., cattle farm isolates) (Belaynehe et al, 2018;Faghri et al, 2018;Rajpara et al, 2018). ISCRs are transposable elements that are a similar size to IS elements, are often associated with class 1 integrons, and are capable of mobilizing adjacent DNA via a rolling-circle mechanism (Bennett, 2008).…”

Antimicrobial use and resistance in Escherichia coli from healthy food-producing animals in Guadeloupe

“…A recent study on a Danish pig production farm clearly indicated that commonly used antimicrobials such as tetracycline, which are not listed as critically important for human treatment can create resistance to critically important antimicrobials, limiting treatment possibilities [23]. A recent metagenomic study on bacterial communities showed that co-selection of resistance to tetracyclines among ESBL producers mobilized conjugative plasmids [24] or integrons [25]. The wide use of tetracyclines in our setting may explain some of the disproportion between the prevalence of resistance and the use of 3rd GC.…”