Genetic diversity, virulence factors and drug resistance of Pantoea strains isolated from samples of fresh fruits, vegetables and soil.

Abstract

Introduction: Pantoea is a genus of Gram-negative bacteria from the Erwiniaceae family. These bacteria are opportunistic human pathogens which are widely distributed in plants and soil. This study aimed to reveal the genetic diversity of Pantoea isolates from food and soil, characterise them biochemically and evaluate their drug resistance.

Material and methods: Thirty Pantoea strains were isolated from fresh fruit (n = 2), fresh and minimally processed vegetables (n = 12) and soil samples (n = 16). The genomic DNA was isolated from cultures on nutrient agar, and species were identified by amplification of 16S ribosomal RNA and housekeeping gene fragments and confirmed by sequencing. Virulence gene presence was determined by amplification of the hcp (haemolysin-coregulated protein), vgrG (glycine-valine repeat sequence G), acrA (anti-clustered regularly interspaced short palindromic repeat protein A) and acrB genes. Isolate drug resistance was tested using the disc-diffusion and gradient strip methods. The presence of Ambler class C (AmpC) β-lactamase (βL) and extended-spectrum (ES) βL resistance genes was tested for.

Results: Five species were identified: P. agglomerans (n = 24), P. ananatis (n = 1), P. eucalypti (n = 1), P. conspicua (n = 1) and P. vagans (n = 2). The hcp and vrgG virulence genes were detected in 7 and 1 strain, respectively. All strains showed high resistance to cephazolin and cephuroxime, and more than half did so to ampicillin. The production of AmpC βL and ESβL was confirmed in 22 and 25 strains, respectively. Three strains of the Pantoea bacteria, including P. ananatis from leeks and P. agglomerans from arugula and soil, showed resistance to three or more antimicrobial classes.

Conclusion: Pantoea spp., including multidrug-resistant strains, in fresh foods pose a potential risk of infection to consumers.