Abstract: [Abstract]    Objective    To investigate the distribution and the antibiotic resistance genes carried by class Ⅰ integron and insertion sequence common region（ISCR1） among clinical isolates of Acinetobacter baumannii. Methods   Fifty-one clinical isolates of multidrug-resistant Acinetobacter baumannii were collected. Polymerase chain reaction method was used to detect the class Ⅰ integrase gene, variable region of classⅠ integron, ISCR1 and genes related to antibiotics resistance located downstream of ISCR1 in 51 multidrug-resistant Acinetobacter baumannii. Antibiotics resistance genes carried by classⅠ integron and ISCR1 were performed by DNA sequencing. The relationship between classⅠ integron and ISCR1 was detected by PCR-mapping. Results Among 51 multidrug-resistant Acinetobacter baumannii isolates, 45 strains were found containing classⅠ integrase genes, 32 strains were found containing variable regions. Sequencing results showed that the gene cassette arrays were aacA4-catB8-aadA1, aacC1-orfA-orf-B-aadA1 and blaPSE-1-aadA2-cmlA1-aadA1. Twenty-two strains were found containing ISCR1 and 5 strains were found containing resistance genes located downstream of ISCR1.
DNA sequencing results showed the resistant gene of qnrA1-ampR. The results of PCR-mapping showed that ISCR1 located directly downstream of 3' conserved segment of classⅠ integron in 20 Acinetobacter baumannii strains. Conclusion ClassⅠ integron and ISCR1 play an important role in mechanisms of drug resistance of Acinetobacter baumannii. ClassⅠ integron and ISCR1 could connect in series in Acinetobacter baumannii.

Key words: Acinetobacterbaumannii, integrons, polymorphism, restriction fragment length, Polymerase chain reaction, insertion sequence common region