Distribution of resistance genotypes of ESBLs-producing Shigella sonnei

Objective To study the resistance mechanism of ESBLs-producing Shigella sonnei for clinical rational use of antimicrobial drugs.Methods A total of 43 strains of multidrug resistant Sh.sonnei(mainly AmpR,SxtR and CtxR) were collected,which were isolated from diarrhea patients at our hospital between 2004 and 2007.Plasmid conjugation experiments were conducted,and the resistance genes were amplified by PCR.Results The test results indicated that 27 of these strains carried CTX-M,16 of which carried CTX-M1 group and 11 carried CTX-M9 group,making up 62.79% of the positive isolated strains.Besides,18 of the tested strains carried TEM genes,accounting for 41.86%,but no SHV,OXA or PER genes were identified.Co-carried CTX and TEM that accounted for 23.26 %.95.35% of the Sh.sonnei carried Class 2 integrons.The success rate of plasmid conjugation experiments was 92.7%.Conclusions ESBLs-producing Sh.sonnei in Beijing carrys mostly CTX-M genes,followed by TEM.The prevalent subtypes are CTX-M-15like,CTX-M-14 and TEM-1.Drug-resistant genes are mainly transmitted through plasmid horizontal transfer.Sh.sonnei carrying CTX-M-27 and CTX-M-64 was identified and reported for the first time in China and in the world.