Integron Analysis and Genetic Mapping of Antimicrobial Resistance Genes in Salmonella enterica serotype Typhimurium
互联网
431
Antimicrobial resistance determinants may be transferred among bacteria via mobile genetic elements including plasmids, transposons, and the more recently explored integrons (
1
). Integrons are naturally occurring genetic elements found as part of the Tn
21
transposon family or located on various broad host-range plasmids (
2
). The fundamental integron structure consists of a 5′-conserved segment (5′-CS) of 1.4-kbp and a 2-kbp 3′-CS (
3
). Between these conserved regions are DNA sequences of variable length and molecular complexity. These intervening sequences are known as
gene cassettes
, and several have now been characterized (Fig. 1 ). Acquisition and dissemination of these genes located within the integron structure, results in an increase in antimicrobial resistance (
4
).
Fig.1.
Schematic representation of a class 1 integron structure. Several gene cassettes (hatched box) have been found located between the 5′- and 3′-CS. Often, more than one open reading frame (ORF) gene cassette can be found within the same integron, in the same orientation, and transcribed from a common promoter located proximal to the 5′-site of insertion.
