The Complex Genetic Context of blaPER-1 Flanked by Miniature Inverted-Repeat Transposable Elements in Acinetobacter johnsonii

On a large plasmid of Acinetobacter johnsonii strain XBB1 from hospital sewage, bla PER-1 and IS CR1 were found in a complex Tn 402 -like integron carrying an arr3 - aacA4 cassette array. The integron was truncated by the same 439-bp miniature inverted-repeat transposable element (MITE) at both ends. bla PER-1 and its complex surroundings might have been mobilized by the MITEst into an orf of unknown function, evidenced by the presence of the characteristic 5-bp direct target repeats. The same 439-bp MITEs have also been found flanking class 1 integrons carrying metallo-β-lactamases genes bla IMP-1 , bla IMP-5 and bla VIM-2 before but without IS CR1 . Although the cassette arrays are different, integrons have always been truncated by the 439-bp MITEs at the exact same locations. The results suggested that MITEs might be able to mobilize class 1 integrons via transposition or homologous recombination and therefore represent a possible common mechanism for mobilizing antimicrobial resistance determinants.