GENETIC-HETEROGENEITY OF PSEUDOMONAS-AERUGINOSA CLINICAL ISOLATES REVEALED BY ESTERASE ELECTROPHORETIC POLYMORPHISM AND RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM OF THE RIBOSOMAL-RNA GENE REGION

The intra-species differentiation of Pseudomonas aeruginosa was analys ed by comparing the polymorphism of esterases by conventional polyacry lamide-agarose gel electrophoresis, the physicochemical properties of the variants of the major esterase P-3 and the restriction fragment le ngth polymorphism of ribosomal RNA gene regions (ribotyping) to O-sero typing for several panels of strains selected from among a series of 2 57 clinical isolates and two references strains, (ATCC nos. 10145 and 27853). The electrophoretic variation of four main kinds of esterase ( P-1-P-4) and 11 additional esterases distinguished by their spectra of hydrolytic activity with synthetic substrates and by their sensitivit y to di-isopropyl-fluorophosphate, allowed the discrimination of 67 zy motypes. Thirty-two esterase P-3 variants were characterised by their pI, electrophoretic mobilities and titration curve analyses. They were distributed into two groups which, by these molecular criteria, seem to be distantly related. Combination of the patterns resulting from Hi ndIII, EcoRI, and BclI restriction endonuclease digestions allowed the discrimination of 33 ribotypes among 134 strains. The strains exhibit ing esterase P-3 variants of group 2 presented a distinct ribotype and belonged to serotype O12. They could constitute a distinct group with in the species. For the majority of the strains, the absence of correl ation between zymotype, ribotype and serotype argues for a high level of heterogeneity within P. aeruginosa and indicates that the parallel use of the first two methods represent a potential tool for epidemiolo gical study.