Molecular Characterization of Integrons in Acinetobacter baumannii : Description of a Hybrid Class 2 Integron

Abstract

Twenty Acinetobacter baumannii strains resistant to various antibiotics were analyzed for integron content and sequences of the amplification products. Sixteen clinical isolates had a class 1 integron, 2 contained an additional class 1 or class 2 integron, but no class 3 integron was detected. Thirteen strains had integrons with a single cassette: aac ( 3 )- Ia (9 strains), ant ( 2 ")- Ia (2 strains), or aac ( 6 ′)- Ib (2 strains); 1 had aac ( 6 ′)- Ib and oxa20 cassettes and an unknown gene; and 1 had an integron containing ant ( 2 ")- Ia and an oxa3 cassette truncated by IS 6100 . The remaining strains harbored class 1 integrons with gene cassettes previously found in Enterobacteriaceae . One integron had a hybrid structure composed of intI2 and the 3′ conserved segment of class 1 integrons. These data indicate that integrons play a major role in multidrug resistance in Acinetobacter .