The cassettes and 3 ' conserved segment of an integron from Klebsiella oxytoca plasmid pACM1

pACM1 is a conjugative multiresistance plasmid from Klebsiella oxytoca that encodes SHV-5 extended-spectrum beta-lactamase (ESBL) and has two integron s. The first is a type I (sul type); the second, detected by hybridization with an intI gene probe, has been putatively identified as a defective type I integron. The cassette region of the first integron has now been fully s equenced and contains three aminoglycoside resistance determinants (aac(6') -Ib, aac(3)-Ia, and ant(3 ")-Ia) and two open reading frames of unknown fun ction. In addition, sequencing of a region downstream from the qacE Delta 1 -sul1-ORF 5 gene cluster of the first integron revealed a copy of insertion sequence IS6100 flanked by inverted copies of sequence from the 11.2-kb in sert (In2) of Tn21. This arrangement is similar to that found in In4 of Tn1 696. The coincidence of an ESBL gene and mobile elements on a conjugative p lasmid has potential implications for the spread of ESBL-mediated drug resi stance, though evidence of bla((SHV-5)) movement mediated by these elements has not been found. (C) 1999 Academic Press.