Integrons and insertion sequence common region 1 (ISCR1) of carbapenem-non-susceptible Gram-negative bacilli in fecal specimens from 5000 patients in southern China.

The integrons and insertion sequence common region 1 (ISCR1) of 329 carbapenem-non-susceptible Gram-negative bacilli, excluding 60 Stenotrophomonas maltophilia strains, in fecal specimens from 5000 patients in southern China were studied. A total of 205 (62.3%) class 1 integron-positive strains and 126 (61.5%) gene-cassette-positive strains were detected, and 44 types of gene-cassette arrays were found, including 8 types described for the first time in the corresponding species and one gene cassette originally detected in integrons, a putative helicase. A total of 9 types of 21 ISCR1-linked resistance gene regions in 35 ISCR1-positive bacilli and 2 previously unreported types of complex class 1 integrons were detected. All strains were extensively drug-resistant. Class 1 integrons and ISCR1 were widely disseminated and these structures carried various resistance genes, which were closely associated with mechanisms of multidrug resistance, including carbapenem resistance.