**Lara Pérez-Etayo 1,\* , Melibea Berzosa 1, David González 1,2 and Ana Isabel Vitas 1,2**


Received: 14 September 2018; Accepted: 18 October 2018; Published: 20 October 2018

**Abstract:** Mobile genetic elements play an important role in the dissemination of antibiotic resistant bacteria among human and environmental sources. Therefore, the aim of this study was to determine the occurrence and patterns of integrons and insertion sequences of extended-spectrum β-lactamase (ESBL)-producing *Escherichia coli* isolated from different sources in Navarra, northern Spain. A total of 150 isolates coming from food products, farms and feeds, aquatic environments, and humans (healthy people and hospital inpatients), were analyzed. PCRs were applied for the study of class 1, 2, and 3 integrons (*intI1*, *intI2*, and *intI3*), as well as for the determination of insertion sequences (IS*26*, IS*Ecp1*, IS*CR1*, and IS*903*). Results show the wide presence and dissemination of *intI1* (92%), while *intI3* was not detected. It is remarkable, the prevalence of *intI2* among food isolates, as well as the co-existence of class 1 and class 2 (8% of isolates). The majority of isolates have two or three IS elements, with the most common being IS*26* (99.4%). The genetic pattern IS*26*–IS*Ecp1* (related with the pathogen clone ST131) was present in the 22% of isolates (including human isolates). In addition, the combination IS*Ecp1*–IS*26*–IS*903*–IS*CR1* was detected in 11 isolates being, to our knowledge, the first study that describes this genetic complex. Due to the wide variability observed, no relationship was determined among these mobile genetic elements and β-lactam resistance. More investigations regarding the genetic composition of these elements are needed to understand the role of multiple types of integrons and insertion sequences on the dissemination of antimicrobial resistance genes among different environments.

**Keywords:** ESBL-producing *E. coli*; β-lactamase genes; antimicrobial resistance; integrons; insertion sequences
