Pathogenic and commensal Escherichia coli from irrigation water show potential in transmission of extended spectrum and AmpC β-lactamases determinants to isolates from lettuce

摘要

There are few studies on the presence of extendedspectrumβ-lactamases and AmpC β-lactamases(ESBL/AmpC) in bacteria that contaminate vegetables.The role of the production environment in ESBL/AmpC gene transmission is poorly understood. Theoccurrence of ESBL/AmpC in Escherichia coli (n = 46)from lettuce and irrigation water and the role of irrigationwater in the transmission of resistant E. coliwere studied. The presence of ESBL/AmpC, geneticsimilarity and phylogeny were typed using genotypicand phenotypic techniques. The frequency ofβ-lactamase gene transfer was studied in vitro.ESBLs/AmpC were detected in 35 isolates (76%).Fourteen isolates (30%) produced both ESBLs/AmpC.Prevalence was highest in E. coli from lettuce (90%).Twenty-two isolates (48%) were multi-resistant withbetween two and five ESBL/AmpC genes. The majorESBL determinant was the CTX-M type (34 isolates).DHA (33% of isolates) were the dominant AmpC βlactamases. There was a high conjugation efficiencyamong the isolates, ranging from 3.5 × 10−2 to1 × 10−2 ± 1.4 × 10−1 transconjugants per recipient.Water isolates showed a significantly higher conjugationfrequency than those from lettuce. A high degreeof genetic relatedness between E. coli from irrigationwater and lettuce indicated possible common ancestryand pathway of transmission.