Integrons play a role in horizontal acquisition and expression of genes, as well as gene reservoir, contributing for the resistance phenotype, particularly relevant to bacteria of clinical importance. We aimed to determine the composition and the organization of the class 1 integron variable region present in Pseudomonas aeruginosa
clinical isolates from Brazil. Strains carrying class 1 integrons were resistant to the majority of antibiotics tested, except to imipenem and ceftazidime. Sequence analysis of the integron variable region revealed the presence of the blaCARB-4
gene into two distinct cassette arrays: aac
XVb gene cassette, which is rare in Brazil and in P. aeruginosa
species, was found in one isolate. PFGE analysis showed the spread of blaCARB-4
among P. aeruginosa
clones. The occurrence of blaCARB-4
XVb in Brazil may contribute for developing resistance to clinically important antibiotics, and shows a diversified scenarium of these elements occurring in Amazon clinical settings, where no study about integron dinamycs was performed to date.