This 1984 study evaluated the use of API biochemical test systems for classifying Erwinia bacteria, a genus containing plant pathogens and epiphytes. Researchers tested 123 Erwinia strains, 6 Enterobacter agglomerans strains, and 22 reference strains using API 20E, API ZYM, and seven additional enzymic API systems, performing a total of 130 biochemical tests. Numerical analysis of the data identified 12 phenons (phenotypic groups), with six containing distinct subphenons. Test reproducibility within the API 20E system ranged from 88 to 100%. The analysis supported recognition of several established Erwinia species as separate taxa, including Er. amylovora, Er. chrysanthemi, Er. stewartii, and Er. cypripedii. However, the authors found no clear distinction between the 'amylovora', 'carotovora', and 'herbicola' groups traditionally used in Erwinia classification. The study also revealed synonymies between certain species pairs and highlighted taxonomic problems with Er. herbicola and Er. rhapontici. Overall, the findings demonstrated that API systems provide a rapid, reliable alternative to conventional phenotypic testing for Erwinia classification and identification.

Key findings

• Numerical analysis of API system data revealed 12 phenons that corresponded well with several established Erwinia species, with test reproducibility ranging from 88-100%
• Traditional classification groups ('amylovora', 'carotovora', 'herbicola') could not be clearly distinguished, indicating inadequacies in current Erwinia taxonomy
• API systems supported the retention of nine Erwinia species as separate taxa and identified synonymies including Er. ananas/Er. uredovora and Er. carotovora subspecies pairs
• API biochemical test systems proved to be a rapid, standardized, and reliable alternative to conventional phenotypic testing for Erwinia identification and classification