Clonal and Plasmid-Mediated Dissemination of β-Lactamases Producing Klebsiella spp. Among Environment and Humans in an Intensive Vegetable Cultivation Area in Eastern China.

Background

Emergence and the rising prevalence of extended-spectrum β-lactamases (ESBLs) producing multidrug-resistant Klebsiella spp. is a global concern.

Methods

391 samples were collected from environmental and people in an intensive vegetable cultivation area in eastern China in June 2019. ESBLs-producing Klebsiella spp. were obtained by PCR and strain identification. The resistance genotype and phenotype of the strain were determined by PCR and drug susceptibility test. The number and size of plasmids were determined by pulsed-field gel electrophoresis assays of plasmids. The plasmid of blaCTX-M was determined by DNA imprinting hybridization, and the transferability of plasmid was understood by plasmid conjugation experiment. Whole-genome sequencing analysis (WGS) was used to obtain other antimicrobial resistance genes, virulence factors, mobile elements, and genetic environment.

Results

Seventeen ESBL-producing Klebsiella spp. were multi-drug resistant. Sixteen ESBLs-producing Klebsiella spp. carried the blaCTX-M, and the size of the plasmid containing the blaCTX-M anged from ∼33.3 kb to ∼244.4 kb. Thirteen ESBLs-producing Klebsiella spp. carried the blaCTX-M were successfully transferred to the recipient bacterium through plasmid mediation. Single nucleotide polymorphism analysis showed clonal transmission between river water (J4-J8) and river sediment (J9), in river water (J3) and human feces (J12). WGS showed that all blaCTX-M were associated with the mobile element Tn3 and/or IS1380 family. All strains carried virulence factors related to adhesion, colonization, and pathogenicity.

Conclusion

This study reminds us that antibiotic-resistant bacteria (ARB) from vegetable cultivation environments can spread to human. It is vital to enhance surveillance of the vegetable cultivation area and high vigilance for the risk of ARB movement from the vegetable plantation environment to humans.