Next generation sequencing and in vivo pathogenicity study of multidrug-resistance efflux pump genesoqxAB-encoding plasmids in Escherichia coli

Background: Multidrug-resistant efflux pump genes oqxAB-encoding plasmids are wildly disseminated in livestock, and also identified in human samples. Giving the high presence in environment and multidrug-resistant nature of oqxAB, deeper understanding of oqxAB-encoding plasmids is necessary.

Objective: To investigate the prevalence, virulence, and phylogenetic of oqxAB-encoding plasmids.

Method: A total of 43 oqxAB carrying Escherichia coli were isolated from human and livestock from China and Hong Kong, these isolates were characterised by disc-diffusion susceptibility test and PCR. The 43 samples were sequenced using PacBio or Illumina platforms, and analysied with five oqxAB-encoding plasmid sequences extracted from Genbank. in vivo pathogenicity study performed by injecting E. coli J53 transconjugants containing oqxAB plasmid into Galleria mellonella larvae.

Result: Among the 48 oqxAB-encoding plasmids, 27 were IncFII F18 plasmids, 12 F16 plasmids, six F33 plasmids, two F24 plasmids, and one F14 plasmid. Virulence regions in plasmids with same Inc group encoded similar set of virulence factors and antibiotic resistance genes. Co-existence of blaCTX-M, fosA3, and oqxAB genes was identified in all F33 plasmids and one F18 plasmid. in vivo pathogenicity study suggested oqxAB plasmids caused significant health deterioration in larvae but no significant increase in death.

Conclusion: Our data shows similar sets of pathogenic factors are frequently co-carried by oqxAB plasmids of same Inc group, suggesting high correlation between plasmids identified from China and Hong Kong. Co-existence of fosA3, blaCTX-M, and oqxAB suggests resistance to most clinical antibiotics. in vivo test indicates oqxAB plasmid can increase pathogenicity of the host bacteria.