Correlation of Elastic Light Scatter pattern analysis of clinical and shellfish strains of Vibrio parahaemolyticus from New Zealand with virulence characteristics

Abstract

Vibrio parahaemolyticus is a leading cause of seafood-associated bacterial gastroenteritis, however not all strains are pathogenic. In New Zealand, strains have been found in locally sourced shellfish, and in both sporadic and outbreak cases of human illness, some due to pandemic sequence types. We evaluate the potential of Elastic Light Scatter (ELS) analysis, a unique approach to examine colony ultrastructure, to identify virulent strains. A set of representative, phylogenetically characterized New Zealand isolates from clinical cases and shellfish were profiled with ELS, and relationships assessed by cluster analysis. Key traits including motility, protease and lipase activities, hemolysis, and halotolerance were also determined. The ELS-based grouping revealed phenotypic differences between strains not evident from their original classification by source of origin. ELS analysis identified two distinct clusters (ELS-1, ELS-2), one of which comprised shellfish strains only; however, ELS-2 contained all clinical strains and several shellfish strains, that exhibited more pronounced swarming and swimming motility results than ELS-1 strains. ELS-1 strains demonstrated wider halotolerance, indicating better adaptation to estuarine environments. Furthermore, most of our shellfish isolates exhibited hemolytic activity, in contrast to those studied of clinical origin. Lipase and protease activities were prevalent among all strains. These findings show that certain virulence traits are present in environmental strains, with wider implications for food and water safety. ELS, combined with phenotypic profiling, may be a powerful tool for rapid screening and risk assessment of potentially pathogenic V. parahaemolyticus strains.