The emergence of extended-spectrum β-lactamase (ESBL)-producing Salmonella London isolates from human patients, retail meats and chickens in southern China and the evaluation of the potential risk factors of Salmonella London

Salmonella is a major foodborne pathogen that causes a broad range of infection in humans and animals. This research was undertaken to investigate the antimicrobial resistance, virulence genes and genotyping of the extended-spectrum β-lactamase (ESBL)-producing Salmonella London (S. London) isolates originating from human patients, retail meats and chickens in southern China. The high antimicrobial resistance rates to trimethoprim/sulfamethoxazole (100%), methoxypyrimidine (100%), sulfaisoxazole (100%), ampicillin (73.68%) and amoxicillin (63.16%) were observed among a total of 19 S. London isolates, and the particular concern is that all isolates exhibited multidrug resistance (MDR). The ESBL-positive phenotype, which is resistant to antibiotics such as ampicillin, ceftazidime and cefotaxime, was observed in the isolates (15/19). These strains harbor the emerging ESBL-coding genes blaSHV, blaTEM-1, blaCTX-M and blaOXA, and co-harbor the virulence genes stn, invA, sseL and virK. In addition, the predominant genotypic virulence profile was characterized by the presence of stn, fimA, virK, invA, sseL, mgtC, siiE and sopB genes in the strains. The profiles of enterobacterial repetitive intergenic consensus (ERIC)-PCR revealed that S. London isolates with genetic diversity were widely disseminated. This study highlights the potential threat to public health posed by the foodborne transmission of the multidrug-resistant S. London isolates from diverse sources.