Genomic traits of Aeromonas veronii isolated from slaughtered Danish broilers

Novel multidrug resistance genomic islands and transposon carrying blaVEB-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 blaVEB-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 blaVEB-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 blaVEB-1 in Aeromonas, and may also evolve by capturing new antimicrobial resistance genes or other mobile genetic elements.

Whole genome sequence analysis of Aeromonas spp. isolated from ready-to-eat seafood: antimicrobial resistance and virulence factors

Aeromonas are widespread in aquatic environments and are considered emerging pathogens in humans and animals. Multidrug resistant (MDR) Aeromonas circulating in the aquatic environment and food production chain can potentially disseminate antimicrobial resistance (AMR) to humans via the foodborne route. In this study, we aimed to investigate AMR and virulence factors of 22 Aeromonas strains isolated from ready-to-eat (RTE) seafood. A multilocus phylogenetic analysis (MLPA) using the concatenated sequences of six housekeeping genes (gyrB, rpoD, gyrA, recA, dnaJ, and dnaX) in the 22 Aeromonas genomes and average nucleotide identity (ANI) analysis revealed eight different species; A. caviae, A. dhakensis, A. hydrophila, A. media, A. rivipollensis, A. salmonicida, A. bestiarum, and A. piscicola. The presence of virulence genes, AMR genes and mobile genetic elements (MGEs) in the Aeromonas genomes was predicted using different databases. Our data showed that the genes responsible for adherence and motility (Msh type IV pili, tap type IV pili, polar flagella), type II secretion system (T2SS) and hemolysins were present in all strains, while the genes encoding enterotoxins and type VI secretion system (T6SS) including major effectors were highly prevalent. Multiple AMR genes encoding β-lactamases such as cphA and bla_OXA were detected, and the distribution of those genes was species-specific. In addition, the quinolone resistance gene, qnrS2 was found in a IncQ type plasmid of the A. rivopollensis strain A539. Furthermore, we observed the co-localization of a class I integron (intl1) with two AMR genes (sul1 and aadA1), and a Tn521 transposon carrying a mercury operon in A. caviae strain SU4-2. Various MGEs including other transposons and insertion sequence (IS) elements were identified without strongly associating with detected AMR genes or virulence genes. In conclusion, Aeromonas strains in RTE seafood were potentially pathogenic, carrying several virulence-related genes. Aeromonas carrying multiple AMR genes and MGEs could potentially be involved in the dissemination and spread of AMR genes to other bacterial species residing in the same environment and possibly to humans. Considering a One-Health approach, we highlight the significance of monitoring AMR caused by Aeromonas circulating in the food chain.