Genetic structures of the B2 and B1 Escherichia coli strains responsible for extra-intestinal infections.

Escherichia coli strains causing human extra-intestinal infections may be divided into two groups, B1 and B2 according to the electrophoretic patterns of carboxylesterase B. This study compares the restriction fragment length polymorphism (RFLP) of ribosomal DNA (rDNA) for 45 B1 strains and 45 B2 strains to examine the genetic structure of B2 strains and to distinguish them from B1 strains. The isolates were chosen for diversity in their allozymes of esterases, B, A, C and I, their production of virulence factors (alpha-haemolysin, mannose resistant haemagglutinin and cytotoxic necrotizing factor) and certain O antigens, and their pathological and geographical origins.

Characterization of Escherichia hermannii by ribosomal DNA restriction fragment length polymorphism.

Ribosomal DNA polymorphism was used to characterize strains of Escherichia hermannii and to differentiate them from E. coli. DNA from 11 E.

Correlation between DNA polymorphism and enzyme polymorphism argues in favour of the delineation of two species within Providencia alcalifaciens.

Ribosomal DNA (rDNA) polymorphism was compared to enzyme polymorphism and DNA/DNA hybridization data for the intraspecies differentiation of Providencia alcalifaciens. DNA from 27 strains previously classified into two zymotypes A1 and A2 and discriminated by two levels of DNA/DNA hybridization (delta Tm values of 0 to 1 degree C and 6 to 10 degrees C, respectively) were analysed by Southern blotting for rDNA polymorphism. The ribotypes fell into two ribogroups A1 and A2, which correlated with the corresponding zymotypes.

Characterization of highly virulent Escherichia coli strains by ribosomal DNA restriction fragment length polymorphism.

Patterns of ribosomal DNA polymorphism were examined to compare carboxylesterase B type B1 strains and B2 strains of Escherichia coli isolated from extra-intestinal infections. DNA from 14 type B2 strains showing the presence of alpha-haemolysin and mannose-resistant haemagglutinin and lethality to mice and 14 type B1 strains lacking these characteristics, was digested with HindIII, EcoRI, BamHI or BglII restriction enzymes and analysed by Southern blotting. The obtained ribotypes clearly differentiated the B2 strains from the B1 strains.

Comparison of molecular epidemiological tools for Branhamella catarrhalis typing.

Twenty-one Branhamella catarrhalis strains selected for their diversity by esterase electrophoretic polymorphism, and belonging to 20 distinct zymotypes, were studied by restriction fragment length polymorphism (RFLP) of total DNA after ethidium bromide staining and of ribosomal DNA regions (ribotyping). The former analysis allowed the distinction of 20 patterns and the latter the delineation of 19 ribotypes. The three methods were correlated and showed a clonal diversity of the species.