A novel integron in Salmonella enterica serovar Enteritidis, carrying the bla(DHA-1) gene and its regulator gene ampR, originated from Morganella morganii

Abstract

The genetic organization of the gene coding for DHA-1 and the corresponding ampR gene was determined by PCR mapping. These genes have been mobilized from the Morganella morganii chromosome and inserted into a complex sulI-type integron, similar to In6 and In7. However, they are not themselves mobile cassettes. This integron probably includes a specific site for recombination allowing the mobilization of diverse resistance genes, as observed for bla(CMY-1) and bla(MOX-1).

FIG. 1

Structure of integron pSAL-1 (9.5 kb) obtained by genetic analysis of the recombinant plasmid pSAL-2_ind and PCR mapping of the upstream region. (A) Sequence reported here (8,558 bp). (B) Recombinant plasmid pSAL-2_ind (4.2 kb). (C) Sequence (2,126 bp) previously reported (5). Open circle, 59-bp element.

FIG. 2

Deletions at the 5′ end of the 3′-CS in In7, In6, and pSAL-1. Base 1 is the first base of the complete 3′-CS. Asterisks indicate sequence identity.

FIG. 3

Comparison of the regions between the common regions of In7, In6, pSAL-1 (DHA-1), pMVP-1 (CMY-1), and pRMOX-1 (MOX-1) and the second 3′-CS of In7, In6, and pSAL-1 (DHA-1). Asterisks indicate sequence identity. Dark gray shading, 100% identity; light gray shading, 92% identity.