Characterization and Control of Erwinia spp. and Pluralibacter sp. in Tuna Salad Preparations

Abstract

Histamine-producing Erwinia and Pluralibacter spp. capable of producing toxic histamine levels were isolated from ingredients commonly used in tuna salad preparations. The characterization and control of these histamine-producing bacteria are necessary to prevent illness from tuna salad consumption. We confirmed the identity of two Erwinia spp. and one Pluralibacter sp. previously isolated from tuna salad ingredients through whole genome sequencing and phylogenic analysis and characterized them for growth and histamine production at different temperatures, pH values, and salt concentrations. In addition, we examined the effects of dried vinegar (DV) powder on growth and histamine production of these strains in inoculated tuna salad preparations. Optimum growth temperatures in tryptic soy broth (TSB) for the two Erwinia spp. and one Pluralibacter sp. were 30.1, 31.1, and 33.98C, respectively, and growth in TSB was observed at 58C for both genera. Optimum histamine production of Erwinia persicina, Erwinia spp., and Pluralibacter spp. in TSB with histidine occurred from 25 to 308C, pH 4 to 6, and 0 to 4% NaCl. No significant growth or histamine production was observed in tuna salad preparations stored at 48C. Growth and histamine production by Erwinia or Pluralibacter spp. was inhibited in tuna salad containing celery and onion and 2% DV, whereas significant growth and histamine production occurred in tuna salad without DV. Understanding optimum growth conditions and histamine production can provide guidance to tuna salad manufacturers in formulating products and adjusting processing conditions that minimize hazards from these histamine-producing bacteria. Addition of 2% DV to tuna salad preparations may prevent histamine production in the event of temperature abuse. HIGHLIGHTS • Isolates were identified as E. persicina, Erwinia spp., and Pluralibacter sp. • Optimum growth of two Erwinia spp. and one Pluralibacter sp. occurred between 30.1 and 35.08C. • Growth in TSB was observed at 58C for both Erwinia spp. and one Pluralibacter sp. • Optimum histamine production occurred from 25 to 308C, pH 4 to 6, and 0 to 4% NaCl. • Growth and histamine production were inhibited in tuna salad with 2% DV added.