Characterization of a Salmonella enterica serovar Agona strain harbouring a class 1 integron containing novel OXA-type β-lactamase (blaOXA-53) and 6′-N-aminoglycoside acetyltransferase genes [aac(6′)-I30]

Abstract

Objective: To characterize by molecular methods a multidrug-resistant Salmonella enterica serovar Agona (S. enterica Agona) isolated from a hospitalized patient in Rio de Janeiro, Brazil. Methods: The S. enterica Agona strain was screened by PCR and DNA sequencing for TEM, SHV and CTX-M-type β-lactamase genes, tet(A), (B), (C) and (D) tetracycline resistance genes, chloramphenicol resistance genes and class 1 integrons. Plasmid characterization was carried out by PCR and Southern hybridization analysis. PCR and PFGE were used to characterize nine other S. enterica Agona strains collected from hospitals in Rio de Janeiro. Results: The study strain was found to harbour a 105kb plasmid, which contained catAl, blaTEM-1, a class 1 integron with two novel genes labelled blaOXA-53 and aac(6′)-130, respectively, and an additional unidentified aminoglycoside resistance gene. A second 53 kb plasmid from the same strain contained tet(D) and blaSHV-5. OXA-53 was shown to provide reduced susceptibility to ceftazidime, and its activity was inhibited in the presence of clavulanic acid. PFGE analysis of the nine other S. enterica, Agona strains revealed two clusters of related strains (78% similarity), and PCR analysis showed that all strains contained the novel integron. Conclusion: An S. enterica Agona strain was found to harbour three plasmid-encoded β-lactamases, one (OXA-53) on a novel class 1 integron that also contains a new aminoglycoside resistance gene, aac(6′)-130. The multidrug resistance plasmids appear to have disseminated to other city hospitals via other S. enterica Agona strains. © The British Society for Antimicrobial Chemotherapy 2004; all rights reserved.