Dissemination and Persistence of bla CTX-M-9 Are Linked to Class 1 Integrons Containing CR1 Associated with Defective Transposon Derivatives from Tn 402 Located in Early Antibiotic Resistance Plasmids of IncHI2, IncP1-α, and IncFI Groups

This study analyzes the diversity of In60, a class 1 integron bearing CR1 and containingbla CTX-M-9 , and its association with Tn402 , Tn21 , and classical conjugative plasmids among 45 CTX-M-9-producing clinical strains (41Escherichia coli strains, 2Klebsiella pneumoniae strains, 1Salmonella enterica strain, and 1Enterobacter cloacae strain). Forty-five patients in a Spanish tertiary care hospital were studied (1996 to 2003). The diversity of In60 and association of In60 with Tn402 or mercury resistance transposons were investigated by overlapping PCR assays and/or hybridization. Plasmid characterization included comparison of restriction fragment length polymorphism patterns and determination of incompatibility group by PCR-based replicon typing, sequencing, and hybridization. CTX-M-9 plasmids belonged to IncHI2 (n = 26), IncP-1α (n = 10), IncFI (n = 4), and IncI (n = 1) groups. Genetic platforms containingbla CTX-M-9 were classified in six types in relation to the In60 backbone and in eight subtypes in relation to Tn402 derivatives. They were associated with Tn21 sequences when located in IncP-1α or IncHI2 plasmids. Our study identifiedbla CTX-M-9 in a high diversity of CR1-bearing class 1 integrons linked to different Tn402 derivatives, often to Tn21 , highlighting the role of recombination events in the evolution of antibiotic resistance plasmids. The presence ofbla CTX-M-9 on broad-host-range IncP-1α plasmids might contribute to its dissemination to hosts that were not members of the familyEnterobacteriaceae .