Histamine Production by Psychrotrophic Pseudomonads Isolated from Tuna Fish

Abstract

Sixty isolates of psychrotrophic bacteria obtained from raw tuna fish were identified as Pseudomonas fluorescens, Pseudomonas putida and non-fluorescent Pseudomonas sp., and were tested for their ability to produce histamine. Following incubation in modified histidine decarboxylase broth, 28% of P. putida, 21% of P. fluorescens and 62% of the non-fluorescent Pseudomonas sp. isolates produced histamine. The maximum amount of histamine produced by a single isolate was 3.2 mg/100 ml, far below the minimum level of 50 mg/100 g believed necessary to induce symptoms of histamine toxicity.