Sequence analysis of multiple-antibiotic-resistant active efflux systemgene acrAB of Salmonella typhi

Objective:To identify the sequence of the multiple-antibiotic-resistant efflux acrAB gene in Salmonella typhi 275(a clinically isolated strain) and analyze its structure,amino acid sequence.Methods:The whole acrAB gene of Salmonella typhi 275 were amplified by PCR with the primers designed from Genebank,and the sequence of products and the amino acid sequence were detected.Results:The whole sequence of acrAB gene of Salmonella typhi 275 contained 5156 bases and 99.38% identity were found in comparison with the reference sequence of Salmonella typhi (Genebank No. AL627267);84.69% identity were detected in comparison with that of Escherichia coli (Genebank No.ECUO0734).The acrR,actA,acrB of Salmonella typhi 275 coded AcrR,AcrA,AcrB proteins with 217,397 and 1049 amino acids,respectively.1 amino acid alteration existed in both AcrA (Ser270Thr)and AcrB (Met964Thr) in comparison with the reference Genebank amino acids sequence.Compared with Escherichia coli,28,33 and 56 amino acids alteration and 86.98%,91.69% and 94.66% identity in the AcrR,Acta and AcrB were found respectively.2 additional amino acids existed in AcrR of Salmonella typhi 275.The promoter region of Acta and acrR was located in 4367-4507 bases and the SD sequence was in 4373-4377 bases.Conclusion:The multiple-antibiotic-resistant active efflux system gene acrAB of Salmonella typhi shows high homology in bases,amino acids and protein structure with that of Escherichia coli and it is the possible reason that Salmonella typhi is resistant to multi-antibiotics without similar chemical structure.