Objectives: We analysed the architecture and probable origin of a class 1 integron from cefotaxime-resistant Morganella morganii isolates.
Methods: bla genes and class 1 integron elements were detected by PCR and DNA-DNA hybridization in a M. morganii strain isolated in 1996. PCR-mapping and sequencing of different fragments were carried out to determine the integron's architecture.
Results and conclusions: A class 1 integron (In116), strongly related to the In6/In7 family, was detected in a plasmid from an oxyimino-cephalosporin-resistant M. morganii strain, producing CTX-M-2 beta-lactamase. The variable region of In116 contains aacA4, bla(OXA-2) and orfD cassettes. Downstream of the 3'-conserved-segment (3'-CS), an orf513-containing common region is followed by bla(CTX-M-2) and flanking regions, having 96-99% nucleotide identity with Kluyvera ascorbata's kluA-1 and neighbouring sequences. Some of the evidence supporting the incorporation of foreign DNA is as follows: a partial deletion in a second 3'-CS (3'-CS2), and the absence of 59-base element or IS-like structures upstream of bla(CTX-M-2).