In99, an In100-related integron, its occurrence and prevalence in clinical Pseudomonas aeruginosa strains from a central region of Portugal.

In99, a possible ancestor of In100, is a class 1 integron associated with carbenicillinase (blaPSE) and aminoglycoside resistance genes [aac(6')-Ib and aadA2]. In99 was present in 8 of 81 clinical isolates of Pseudomonas aeruginosa from unrelated patients collected in different years. The strains fell into two clonal groups and exhibited resistance to beta-lactams and aminoglycosides.