Partial characterization of a genomic island associated with the multidrug resistance region of Salmonella enterica Typhymurium DT104

Abstract

This study describes the identification of the insertion site and partial characterization of a 43-kb region harboring the genes associated with the penta-resistant phenotype of a Canadian isolate of Salmonella enterica Typhymurium DT104 labelled 96-5227. The 43-kb fragment, here referred to as Salmonella genomic island I (SgiI), was found in the genome of S. enterica Typhymurium between the thdf and a prophage CP-4-like integrase (int2) gene and is flanked by an imperfect 18-bp direct repeat. A region downstream of sulI in the right end of SgiI contained four open reading frames which includes an IS6100 element, and a 2-kb region from the left end contained two open reading frames which showed homology to an integrase and an excisionase. Furthermore, a 1.9-kb retron sequence located between int2 and yidY was identified which may be unique to the S. enterica Typhymurium genome. The int-retron sequence is flanked by a 27-bp imperfect direct repeat. ß

Emergence of Salmonella epidemics: The problems related to Salmonella enterica serotyp Enteritidis and multiple antibiotic resistance in other major serotypes

“…The ApCmFfStSpSuTc multiple-antibiotic resistance profile of S. Typhimurium DT104 is conferred by an antibiotic resistance gene cluster carried by a chromosomal genomic island called Salmonella genomic island 1 (SGI1) [20,21]. The 43 kb-size SGI1 is located between the thdF and int2 genes of the chromosome of S. Typhimurium DT104 and is flanked by an imperfect 18-bp direct repeat (Fig.…”

“…The thdF gene codes for a thiophene-and furan-oxidation protein. The int2 gene, a prophage CP-4-like integrase gene, is part of a retron sequence which has to date been reported only in strains of serotype Typhimurium [20]. The antibiotic resistance gene cluster is located near the 3' end of SGI1 and constitutes a complex class 1 integron belonging to the In4 group.…”

Molecular characterization, spread and evolution of multidrug resistance in Salmonella enterica Typhimurium DT104

“…More recently this chromosomal antibiotic resistance gene cluster has been shown to be part of a 43-kb genomic island termed Salmonella genomic island I (SgiI) [10]. By comparison with the genome sequence of S. enterica Typhimurium LT2, SgiI has been found in the genome between the thdf gene, coding for a thiophene and furan oxidation protein, and a prophage CP-4-like integrase gene (int2), and is flanked by an imperfect 18-bp direct repeat [10].…”

“…By comparison with the genome sequence of S. enterica Typhimurium LT2, SgiI has been found in the genome between the thdf gene, coding for a thiophene and furan oxidation protein, and a prophage CP-4-like integrase gene (int2), and is flanked by an imperfect 18-bp direct repeat [10]. Downstream of SgiI, a 1.9 kb retron sequence was located between genes int2 and yidY -coding for a putative drug translocase -of the S. enterica Typhimurium genome.…”

“…Downstream of SgiI, a 1.9 kb retron sequence was located between genes int2 and yidY -coding for a putative drug translocase -of the S. enterica Typhimurium genome. This retron sequence may be unique to S. enterica serovar Typhimurium since it has not been detected in other S. enterica serovars [10]. The SgiI comprises a number of genes -with no known functions and no homologies with other proteins in databases -which might contribute to virulence as seen with the Salmonella pathogenicity islands (M. Mulvey, personal communication).…”