Co-spread of metal and antibiotic resistance within ST3-IncHI2 plasmids from E. coli isolates of food-producing animals

Abstract

Concerns have been raised in recent years regarding co-selection for antibiotic resistance among bacteria exposed to heavy metals, particularly copper and zinc, used as growth promoters for some livestock species. In this study, 25 IncHI2 plasmids harboring oqxAB (20/25)/blaCTX-M (18/25) were found with sizes ranging from ∼260 to ∼350 kb and 22 belonged to the ST3-IncHI2 group. In addition to blaCTX-M and oqxAB, pcoA-E (5/25) and silE-P (5/25), as well as aac(6′)-Ib-cr (18/25), floR (16/25), rmtB (6/25), qnrS1(3/25) and fosA3 (2/25), were also identified on these IncHI2 plasmids. The plasmids carried pco and sil contributed to increasing in the MICs of CuSO4 and AgNO3. The genetic context surrounding the two operons was well conserved except some variations within the pco operon. The ~32 kb region containing the two operons identified in the IncHI2 plasmids was also found in chromosomes of different Enterobacteriaceae species. Further, phylogenetic analysis of this structure showed that Tn7-like transposon might play an important role in cross-genus transfer of the sil and pco operons among Enterobacteriaceae. In conclusion, co-existence of the pco and sil operons, and oqxAB/blaCTX-M as well as other antibiotic resistance genes on IncHI2 plasmids may promote the development of multidrug-resistant bacteria.

Characterization of a Novel IncHI2 Plasmid Carrying Tandem Copies of bla CTX-M-2 in a fosA6 -Harboring Escherichia coli Sequence Type 410 Strain

“…S1). ST3-IncHI2 plasmids are reportedly widely disseminated in Chinese poultry and livestock farms, and they carry fosA3, bla CTX-M-9 -group genes (bla CTX-M-14/65/27 ), and/or oqxAB (17,19). In previous studies, ST1-IncHI2 plasmids were associated with bla CTX-M-9 in Europe, while ST2-or APEC-O1-R-type IncHI2 plasmids linked to bla CTX-M-2 were found in Salmonella spp.…”

“…KT347600.1) (15), bla VIM (accession no. LN555650.1) (16), bla IMP , armA, qnrA, oqxAB, fosA3, and mcr-1 (12,(17)(18)(19)(20)(21). So far, no IncHI2 plasmid carrying bla CTX-M-2 has been characterized fully.…”

Regulation of conjugative transfer of plasmids and integrative conjugative elements

“…The relaxase, with the DNA strand attached, transfers to the recipient cell through the pore formed by the T4SS, finally the plasmid needs to be established in the recipient, with the help of ssDNA binding, anti-restriction and SOS inhibition proteins to generate stable transconjugants. (Alvarez-Martinez and Christie, 2009;Ding and Hynes, 2009;Frost et al, 2005;Koraimann and Wagner, 2014). It is interesting to note that expression of transfer genes is induced in a subset of the bacterial population, maybe diminishing the negative effects of the associated energy cost (Koraimann and Wagner, 2014).…”

“…Conjugative plasmids and ICEs from Gram-negative bacteria usually carry all the structural genetic elements required to perform transfer (an oriT site, Dtr and Mpf genes) (Frost et al, 2005). In Gram-positive bacteria, there are two different systems (Goessweiner-Mohr et al, 2014).…”

IncHI2 Plasmids Are the Key Vectors Responsible for oqxAB Transmission among Salmonella Species

“…However, oqxAB-positive IncHI2-ST3 plasmids were mainly reported in this study. Nevertheless, a recent publication reported that most IncHI2-oqxAB-bla CTX-M-9 plasmids in E. coli belong to IncHI2-ST3 (18). It is suggested that the IncHI2 plasmids undergo constant evolvement and dissemination within various bacterial species.…”