Class 1 integron gene cassettes in multidrug-resistant Gram-negative bacteria in southern China

Non-duplicate multidrug-resistant Gram-negative bacteria (n = 1447) isolated from January 2008 to December 2009 were investigated for the presence of integrons as well as characterisation of gene cassettes. Among 825 strains carrying the class 1 integrase gene intI1, 461 gene cassette-positive isolates were found. Thirty-eight distinct gene cassette arrays were identified by restriction fragment length polymorphism (RFLP) and DNA sequencing analyses. In addition, several novel gene cassette arrays detected in this study were reported for the first time in some species: one in Escherichia coli, six in Klebsiella pneumoniae, six in Enterobacter cloacae, three in Enterobacter aerogenes, one in Proteus mirabilis, one in Acinetobacter spp., one in Stenotrophomonas maltophilia and one in Pseudomonas putida. Among them, three cassettes, including HAD-like, ΔMFS-1 and qnrVC-like genes, were originally detected in integrons.