OBJECTIVE To investigate the distribution of integron in Gram-negative isolates which are causing nosocomial infection the association with drug resistance,and it′s contribution in horizontal transfer of drug resistance.METHODS Drug resistance test was performed by K-B method.ESBL-positive strains were detected by double-disk synergy test.Integron was determined by PCR assay with integron-specific-primer.Conjugative transfer test,plasmid profile analysis,nested-PCR,and DNA sequence analysis were used to investigate the transferable mechanism of integron mediated.RESULTS 66.4% of Strains were shown to be positive for classes Ⅰ integron,no class Ⅱ and Ⅲ integrons were detected.Profiles of class Ⅰ integron were 11 types,which sized from 700bp to 2300bp,gene cassettes included genes encoding resistance to aminoglycosides(aadA1,aadA2,aadA5 and aacA4),sulfamethoxazole/trimethoprim(dfrA12,dfrA5 and dfrA17) and chloramphenicol(catB8).Strains positive for class Ⅰ integron were highly related to multidrug resistance and ESBLs.Class Ⅰ integron could horizontal transfer along with plasmid among bacteria.CONCLUSIONS Class 1 integron is widespread in Gram-negative isolates which are causing nosocomial infection.Drug resistance is more liable to horizontal transfer via class Ⅰ integron along with plasmid.It implies the necessary for surveillance of horizontal transfer of antibiotic resistance gene among bacteria genus.