ABSTRACT
Objective To detect the influence of marOR mutations on antibiotic resistance in Shigella spp. Methods The marOR gene with four-base deletion was amplified by overlap PCR, then inserted in a T-vector and transformed into DH5α. The clone of marOR gene with four-base deletion and three point mutations was prepared from the strain having these mutations. Electrophoresis and sequencing were preformed to certify the correction of the cloned genes. Drug susceptibility tests were preformed for the strains harbouring the different clones [DH5α, DH5α (T), DH5α (marOR), DH5α (marOR-CATT), DH5α(marOR-CATT + 3m)]. Results Compared with the control strain (DH5α-T), the antibiotic resistances of marOR with four-base deletion [DH5α (marOR-CATT)] were higher to streptomycin, tobramycin, cefazolin and cefalexin, and the antibiotic resistances of marOR with four-base deletion and three point mutations [DH5α (marOR-CATT + 3m)] were higher to streptomycin and to tetracycline. The antibiotic resistances of DH5α (marOR-CATT) and DH5α (marOR-CATT +3m) to streptomycin, tetracycline, chloramphenicol, cefazolin, levofloxacin, ciprofloxacin and norfloxacin were higher than DH5α (marOR). The diameters of the antibiotics except the trimethoprim between DH5α (marOR-CATT) and DH5α (marORCATT +3m) had not significant disparity. Conclusion The four-base deletion in 1376-1379 sites of the marOR gene increased the resistance of Shigella spp to some antibiotics. The point mutations in 1411, 1417,1435 sites of the marOR gene have little influence on the antibiotic resistance of Shigella spp.