Analysis on mar gene mutation in mult-drug resistant Shigella / 中华微生物学和免疫学杂志

ABSTRACT

Objective To study the association of multi-drug resistance with mutations in mar gene in clinical isolates of Shigella.Methods Fifty-four clinical isolates of Shigella were collected.Susceptibility tests of tetracycline(TE),chloramphenieol(C),ampicillin(AM),cipr ofloxacin(CIP),and norfloxacin(NOR)were performed in a11 isolates.Hexane and cyclohexane were used to study the organic solvent tolerance of all clinical isolates.marOR genes of these strains were analyzed by potymerase chain reaction-single strand conformation polymorphism(PCR-SSCP)and were sequenced. Results Thirty-five multi-drug resistant strains were identified,and the rate of multi-drug resistance was 64.8%.Thirty-eight of 54 strains were tolerant to organic solvent,including 33 multi-drug resistance strains,3 drug resistant strains and 2 sensitive strains. marOR gene was found in all strains by PCR, and 5 multi-drug resistant strains,(14.29%)carrying marOR gene mutations in multi-drug resistant strains were found by SSCP analysis.DNA sequence analysis of marOR gene revealed that there was a 4 base deletion from base 1376 to 1379 in marO gene that resulted in frame-shift mutation.However,this deletion mutation didn;t exist in the standard strain S51250 and sensitive strains.There were 10 point mutations of marR gene in multi-drug resistant strains,2 of them resulting in amino acid changes1752(G→A)Gly→ser,1854(T→c)Tyr→His.The rest mutations were all nonsense,and some of them occurred in sensitive strains or in many other strains.Conclusion The marO gene mutation may play an important role in the regulation of multi-drug resistance in Shigella spp.