Clonal structure of Providencia alcalifaciens strains isolated from diarrhoeal stools in São Paulo, Brazil.

Clonal analysis based on ribotyping demonstrated that Providencia alcalifaciens strains isolated mainly from diarrhoeal stools in São Paulo, Brazil, were clustered into two main groups. Eleven distinct ribotype patterns were identified with ClAI, EcoRV and MluI restriction endonucleases. P. alcalifaciens strains with invasive properties were of two ribotype patterns that differed from those identified among non-invasive strains. The ribotyping results confirmed that P. alcalifaciens strains associated with diarrhoeal disease in São Paulo represent distinct groups of strains. Although the invasive strains were isolated from different patients over an extended period they were clustered into two genetically related clones, which seemed to be distributed endemically in the population studied.