Extended-spectrum β-lactamase-producing Escherichia coli from extraintestinal infections in humans and from food-producing animals in Italy: a 'One Health' study

In recent years, Escherichia coli producing extended spectrum beta-lactamases (ESBL) have become a serious public health problem and food-producing animals (FPA) have been suggested as a potential reservoir/source. In this study, we aimed to compare ESBL-producing E. coli isolates from different sources. ESBL-producing E. coli isolates were collected from humans (n=480) and FPA (n=445) in Italy (2016-2017). Isolates were screened for the presence of ESBL and carbapenemase genes and classified according to phylogenetic group and MLST genotyping. mcr-1 to -5 genes were searched for in colistin resistant isolates. CTX-M was the most frequent ESBL-type in both human and animal isolates. CTX-M-15 prevailed in humans (75%) and cattle (51.1%) but not in poultry (36.6%). CTX-M-1 was common (58%) in pigs. SHV-type and CMY-2-like were found in FPA, especially in poultry (17.0% and 29.9%, respectively). 29 isolates were mcr-1 carriers (3 from humans and 26 from FPA). No carbapenemase genes were detected. Human isolates mostly belonged to phylogroup B2 (76.5%). Animal isolates were distributed among groups A (35.7%), B1 (26.1%) and C (12.4%). Few animal isolates (almost all from poultry) were classified into group B2 (4.3%). Most human isolates (83.4%) belonged to the pandemic ST131 clone and frequently carried CTX-M-15 (75.9%). ST131 was rarely detected in FPA (n=3 isolates from poultry). Nineteen STs were shared in both sources with ST10, ST410 and ST69 being more frequently detected. According to our results the potential exchange of ESBL genes from animals to humans is feasible, underlying the need for a strict monitoring based on an "One Health" approach.