Novel multidrug resistance genomic islands and transposon carrying bla_VEB-1 identified in mcr-positive Aeromonas strains from raw meat in China

Objectives To characterize the genetic environments of ESBL gene blaVEB-1 in mcr-positive Aeromonas strains from raw meat in China. Methods Whole genomes of Aeromonas strains were sequenced using the Illumina or Nanopore platforms. Genetic environments of bla(VEB-1) were analysed using the BLAST program. Results The blaVEB-1 gene was detected in five Aeromonas strains carrying the mcr-7-like gene. WGS revealed that all bla(VEB-1) genes were located on Aeromonas chromosome, and were carried by two novel different genomic islands named Aeromonas veronii genomic islands AveGI1 and AveGI2, as well as one transposon named Tn7690. AveGI1 is a new member of the Salmonella genomic island 1 family, incorporated into the 3'-end of mnmE (trmE). AveGI2 is a novel genomic island that has a size of 23 180 bp and is incorporated into the 3'-end of syd. The MDR regions of AveGI1 and AveGI2 are two different class 1 integrons containing 10 and five resistance genes, respectively. Tn7690 is a Tn1722 derivative containing In4-type integron and Tn5393, which harbours 10 resistance genes and integrates into different positions on the chromosomes of three strains with the capacity for mobility. Conclusions We report chromosomally located novel MDR genomic islands and transposon that carry blaVEB-1 in mcr-positive Aeromonas strains. These genetic elements may mediate the spread of bla(VEB-1) in Aeromonas, and may also evolve by capturing new antimicrobial resistance genes or other mobile genetic elements.