Novel class 1 integron (InS21) carrying blaCTX-M-2 in Salmonella enterica serovar infantis

Abstract

The genetic organization of the region coding for CTX-M-2 in Salmonella enterica serovar Infantis was determined by PCR mapping. This gene seems to have been mobilized from the Kluyvera ascorbata chromosome to a complex sulI-type integron, similar to In6 and In7.

FIG. 1.

Schematic drawing of the class 1 integrons In6, In7, pSAL-1, and InS21. In the sequence at the boundary, the boldface text corresponds to conserved nucleotides. Deletions correspond to the 5′ end of the second 3′-CS region. Arrows indicate the direction of transcription.

FIG. 2.

PCR mapping strategy and resulting structure of InS21. Numbers in italics correspond to the approximate sizes (in kilobases) of the PCR products. Numbers at both ends of each PCR product indicate the pair of primers used for the different PCR amplifications. Dashed boxes correspond to the common region, whereas striped boxes indicate the region (bla_CTX-M-2 and ORF 3) having homology with kluA-1 and flanking regions. Arrows indicate the direction of transcription. Cloned inserts used for sequencing are indicated with the plasmid designation given to each construct.

FIG. 3.

Sequence alignments of the second 3′-CS 5′ ends for the consensus sequence (19) of that region in In6, In7, pSAL-1, and the proposed InS21. Asterisks indicate sequence identity. The start codon for qacEΔ1 gene is underlined, and the sequence of ORF 3 in InS21 is double underlined.