Transmissible ST3-IncHI2 Plasmids Are Predominant Carriers of Diverse Complex IS26-Class 1 Integron Arrangements in Multidrug-Resistant Salmonella

Abstract

Diverse mobile genetic elements (MGEs) including plasmids, insertion sequences, and integrons play an important role in the occurrence and spread of multidrug resistance (MDR) in bacteria. It was found in previous studies that IS26 and class 1 integrons integrated on plasmids to speed the dissemination of antibiotic-resistance genes in Salmonella. It is aimed to figure out the patterns of specific genetic arrangements between IS26 and class 1 integrons located in plasmids in MDR Salmonella in this study. A total of 74 plasmid-harboring Salmonella isolates were screened for the presence of IS26 by PCR amplification, and 39 were IS26-positive. Among them, 37 isolates were resistant to at least one antibiotic. The thirty-seven antibiotic-resistant isolates were further involved in PCR detection of class 1 integrons and variable regions, and all were positive for class 1 integrons. Six IS26-class 1 integron arrangements with IS26 inserted into the upstream or downstream of class 1 integrons were characterized. Eight combinations of these IS26-class 1 integron arrangements were identified among 31 antibiotic-resistant isolates. Multidrug-resistance plasmids of the IncHI2 incompatibility group were dominant, which all belonged to ST3 by plasmid double locus sequence typing. These 21 IncHI2-positive isolates harbored six complex IS26-class 1 integron arrangement patterns. Conjugation assays and Southern blot hybridizations confirmed that conjugative multidrug-resistance IncHI2 plasmids harbored the different complex IS26-class 1 integron arrangements. The conjugation frequency of IncHI2 plasmids transferring alone was 10−5-10−6, reflecting that different complex IS26-class 1 integron arrangement patterns didn't significantly affect conjugation frequency (P > 0.05). These data suggested that class 1 integrons represent the hot spot for IS26 insertion, forming diverse MDR loci. And ST3-IncHI2 was the major plasmid lineage contributing to the horizontal transfer of composite IS26-class 1 integron MDR elements in Salmonella.

Diverse Mobile Genetic Elements and Conjugal Transferability of Sulfonamide Resistance Genes (sul1, sul2, and sul3) in Escherichia coli Isolates From Penaeus vannamei and Pork From Large Markets in Zhejiang, China

“…On contrary, all 12 strains collected from pork samples had different pulsotypes, demonstrating wide genomic diversity. The possible non-clonal dissemination of sul genes in E. coli isolates from pork samples might be effected by MGEs via horizontal gene transfer (HGT) (Zhao et al, 2018). However, further genomic analysis is necessary to confirm this hypothesis.…”

“…ISs are the simplest autonomous MGEs capable of altering the expression of neighboring genes (Zhao et al, 2018). In the present study, 87.5% (35/40) of sul gene-related fragments were found to carry ISs belonging to a variety of families in diverse sites.…”

Escherichia coli ST302: Genomic Analysis of Virulence Potential and Antimicrobial Resistance Mediated by Mobile Genetic Elements

“…We were able to map all F2_18C horizontally transferred ARGs to a 274, 059 bp circular plasmid, pF2_18C_HI2 ( Figure 6A). This plasmid was typed by pMLST as HI2:ST3, a lineage known as a major contributor in transferring complex class 1 integrons conferring AMR (Zhao H. et al, 2018) pF2_18C_HI2 is very similar to three HI2:ST3 plasmids circulating in Australian pig farms (Dyall-Smith et al, 2017;Billman-Jacobe et al, 2018;Wyrsch et al, 2019) (Figure 6A). pF2_18C_H12 carries the same AMR profile as pSDE-SvHI2, isolated from a severe ETEC strain (Wyrsch et al, 2019), and differs to a pSDC-F2_12BHI2, isolated from a commensal E. coli strain (Wyrsch et al, 2019), and pSTM6-275, isolated from Salmonella enterica subsp.…”

Genomic Characterisation of a Multiple Drug Resistant IncHI2 ST4 Plasmid in Escherichia coli ST744 in Australia

“…Additionally, pRDB9 carried the mcr-1 gene embedded in the composite transposon Tn 6330 . These and other observations highlight how highly similar plasmids adjust to the antimicrobial selection pressures imparted onto the host bacterium by altering the resistance gene cargo they carry [ 72 , 73 ].…”