OPRL1 and cystic fibrosis: The oprL, HW2 and HW3 PCR primer sets were then used to screen a larger collection of P. aeruginosa strains including a further 38 CF isolates that had been previously profiled by PFGE typing to be either AES-I (18) or non-AES-I (20) [1,10], 9 representatives of the Liverpool, Manchester, Midlands, Stoke, Trent and Australian pulsotype II epidemic strains [2,8,27] as well as another 52 non-CF clinical isolates (Table 3).