COMPARATIVE USEFULNESS OF RIBOTYPING, EXOTOXIN-A GENOTYPING, AND SALIRESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM ANALYSIS FOR PSEUDOMONAS-AERUGINOSA LINEAGE ASSESSMENT

Ribotyping, exotoxin A genotyping (EAGP), and restriction fragment len gth polymorphism (RFLP) analysis of total DNA with SalI (SalI RFLP) we re compared for intraspecics discrimination of 93 Pseudomonas aerugino sa isolates. Type-ability of all methods was 100% and the results of t yping with each method remained unchanged during laboratory manipulati on. Clonal groups defined with each molecular method were largely coin cident and, in those cases where inconsistencies were detected, isolat es were analyzed by transverse alternating field gel electrophoresis ( TAFE) and arbitrarily primed polymerase chain reaction (AP-PCR). SalI RFLP analysis was highly discriminative so as to distinguish unrelated isolates of close lineage. However, it was not a good method to ident ify isolates of unrelated lineage because SalI RFLP appealed to be sub jected to convergent evolution. The index of discrimination suggested by Hunter and Gaston was determined to assess the discriminatory power of the molecular methods utilized either alone or in several combinat ions. Combined use of ribotyping and SalI RFLP analysis reached the hi ghest index of discrimination (0.982) and proved to be a very valuable tool for epidemiological differentiation of P. aeruginosa isolates.