Class 1 and 2 Integrons in Escherichia coli Strains Isolated from Diarrhea and Bacteremia in Children Less Than 2 Years of Age from Peru

Class 1 and Class 2 integrons are mobilizable elements able to carry a variety of antibiotic resistance determinants. In the present study, Class 1 and 2 integrons present in 355 pathogenic Escherichia coli (285 diarrheagenic, of these 129 were enteropathogenic, 90 enteroaggregative, 66 enterotoxigenic, and 70 bacteremic) isolated from healthy and ill children under age 5 from periurban areas of Lima, Peru, were characterized. The presence of integrase 1 and 2 was established by polymerase chain reaction (PCR), and variable regions were grouped by PCR-restriction fragment length polymorphism and subsequent sequencing. Antimicrobial resistance was established by disk diffusion. Ninety-seven isolates (27.3%) presented integrase 1, and 16 (4.5%) presented integrase 2 (P, 0.0001); in addition, seven (2.0%) isolates, six diarrheagenic and one bacteremic, presented both integrase genes. The presence of integrase 1 was more frequent among bacteremic isolates (P 5 0.0004). Variable regions were amplified in 76/120 (63.3%) isolates with up to 14 gene arrangements. The most prevalent gene cassettes were those encoding dihydrofolate reductases as well as aminoglycoside modifying enzymes. Of note, Class 1 integrons tended to be associated with the presence of extended-spectrum b-lactamases (ESBLs). A variety of Class 1 and 2 integrons were detected in diarrheagenic and bacteremic E. coli, demonstrating the heterogeneity of variable regions circulating in the area. The association of integrons with ESBLs is worrisome and has an impact on the development of multidrug resistance.