Abstract
On a large plasmid of Acinetobacter johnsonii strain XBB1 from hospital sewage, bla PER-1 and ISCR1 were found in a complex Tn402-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 ISCR1. 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.
Highlights
BlaPER-1 encodes the extended-spectrum b-lactamase (ESBL) PER-1 conferring resistance to penicillins, cephalosporins and monobactams [1] and has been found in Aeromonas spp., Acinetobacter baumannii, Alcaligenes faecalis, Pseudomonas aeruginosa and the Enterobacteriaceae in Asia and Europe [2,3]
In XBB1, blaPER-1 was carried by a 399 kb large plasmid, which had been completely sequenced, assembled and circularized. blaPER-1 was found downstream of the insertion sequence ISCR1 in a 5.7 kb region that included gts, abct and four genes of unknown function in a complex Tn402-like class 1 integron with the arr3 and aacA4 cassettes (Figure 1)
The two miniature inverted-repeat transposable element (MITE), which were in the same direction, might have formed a composite transposon-like mobile element mediating the transposition of the complex Tn402-like class 1 integron containing ISCR1 and blaPER-1 into a gene of unknown function as evidenced by the presence of characteristic 5 bp (GTTGC) direct target repeats (DR, Figure 1)
Summary
BlaPER-1 encodes the extended-spectrum b-lactamase (ESBL) PER-1 conferring resistance to penicillins, cephalosporins and monobactams [1] and has been found in Aeromonas spp., Acinetobacter baumannii, Alcaligenes faecalis, Pseudomonas aeruginosa and the Enterobacteriaceae in Asia and Europe [2,3]. BlaPER-1 was found downstream of the insertion sequence ISCR1 in a 5.7 kb region that included gts (encoding a glutathione S-transferase), abct (encoding an ABC-type transporter) and four genes of unknown function in a complex Tn402-like class 1 integron with the arr3 and aacA4 cassettes (Figure 1).
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