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Characterization of Erwinia chrysanthemi from a Bacterial Heart Rot of Pineapple Outbreak in Hawaii

The first reported outbreak of bacterial heart rot of pineapple (Ananas comosus var. comosus) in Hawaii occurred in December 2003. Of immediate concern was the differentiation of heart rot caused by Erwinia chrysanthemi from a soft rot caused by E. carotovora subsp. carotovora because of regulatory issues. Presumptive identifications of the isolated bacteria were made using bacteriological tests (including reactivity with an Erwinia-specific monoclonal antibody, E2) and compared with identifications obtained by two general methods: carbon source utilization profiling (Biolog) and 16S rDNA sequence analysis. The panel of bacteriological tests consistently differentiated E. chrysanthemi from E. carotovora subsp. carotovora and other nonquarantine organisms. BOX-polymerase chain reaction fingerprint patterns further differentiated the pineapple-isolated E. chrysanthemi strains from those obtained from other plants and irrigation water. Pineapple leaf inoculations revealed that only E. chrysanthemi from pineapple produced watersoaking and rot similar to that observed on the original symptomatic plants, thus identifying these strains as the causal agents of the outbreak. In this situation, where rapid identification of an unknown pathogen was necessary, standard bacteriological tests then available in the laboratory provided reliable differentiation of E. chrysanthemi from E. carotovora subsp. carotovora. Additional strain characterization is needed before the pineapple-isolated E. chrysanthemi strains can be classified into a species of the new genus Dickeya.