Integrative conjugative elements mediate the high prevalence of tmexCD3-toprJ1b in Proteus spp. of animal source.

Integrative conjugative elements (ICEs) are important mobile elements that are associated with the dissemination of antibiotic resistance genes (ARGs) in . Recent studies demonstrated that the tigecycline resistance gene cluster has emerged in ICEs of . However, the prevalence of positive from animal sources is unclear. To cover the gap, a total of 762 spp. were isolated from animal source from six provinces of China to identify the positive isolates. Eight positive isolates were identified, with the positive rate of 1.05% against all spp. and 2.79% against ICE-bearing spp. The gene cluster in these spp. were and all of them were carried by ICEs. Genetic structure analysis showed that -bearing ICEs were complicated and plastic, but the was specifically integrated into variable region III (VRIII) of ICEs with the help of integrases. Furthermore, we found that the gene, which is presented in VRIII of ICEs and other genetic structures of many other bacterial genomes, was a hotspot for the integration of -bearing potential mobile elements. In summary, our results suggested that were important reservoirs for due to the high prevalence of ICEs. Therefore, continuous surveillance of ICEs-associated ARGs in is necessary and significant for controlling their future transmission. IMPORTANCE The emergence and spread of have greatly weakened the function of tigecycline. Although studies have demonstrated the significance of as carriers for , the epidemic mechanism and characteristics of in remain unclear. Herein, we deciphered that the gene in VRIII of SXT/R391 ICEs was a hotspot for the integration of -bearing mobile genetic elements by genomic analysis. The mobilization and dissemination of in were mediated by highly prevalent ICEs. Furthermore, the co-occurrence of -bearing ICEs with other chromosomally encoded multidrug resistance gene islands warned that the chromosomes of are significant reservoirs of ARGs. Overall, our results provide significant insights for the prevention and control of in .