Identification and characterization of Salmonella genomic island 1 among Salmonella strains from healthy persons

Objective To identify and characterize Salmonella genomic island 1(SGI1) in Salmonella strains from healthy person,and to analyze the relationship between SGI1 and antibiotic resistance.Methods Five class 1 integron positive strains were tested for the presence of SGI1 with PCR method,and the positive amplicons were sequenced and analyzed.To detect the mobilization of the SGI1,the extrachromosome circle forms or the excision as well as conjugation and natural genetic transformation were examined.Results SGI1 was detected in a Salmonella enterica serovar Typhoid murine strain,with the aadA2,floR,tetG,and blaPSE-1 genes in its multidrug-resistant region,and it was located between thdF and a retronphage(int2).Both the extrachromosome circle form of SGI1 and the excision of SGI1 were detected,and it could transfer through natural genetic transformation.Conclusion The presence of SGI1 in Salmonella strains from healthy person suggests that widespread surveillance of antibiotic resistance should be conducted at the gene level.