Histamine and biogenic amine production by Morganella morganii isolated from temperature-abused albacore

Histamine-producing bacteria were isolated from albacore stored at 0, 25, 3 0, and 37 degrees C. They were screened using Niven's differential medium, and their histamine production was confirmed by high-pressure liquid chroma tography analysis. The optimum temperature for growth of histamine-producin g bacteria was 25 degrees C. The bacterium producing the highest level of h istamine was isolated from fish abused at 25 degrees C. It was identified a s Morganella morganii by morphological, cultural, biochemical, and antimicr obial characteristics and by the Vitek microbial identification system. The M. morganii isolate was inoculated into tuna fish infusion broth medium, a nd the effect of temperature was determined for microbial growth and format ion of histamine and other biogenic amines. The isolate produced the highes t level of histamine, 5,253 ppm, at 25 degrees C in the stationary phase. A t 15 degrees C, histamine production was reduced to 2,769 ppm. Neither micr obial growth nor histamine formation was detected at 4 degrees C. To determ ine whether the isolate can also produce other biogenic amines that can pot entiate histamine toxicity, production of cadaverine, putrescine, serotonin , tryptamine, tyramine, phenylethylamine, spermidine, and spermine by the i solate was also monitored. Cadaverine, putrescine, and phenylethylamine wer e detected with microbial growth in the tuna fish infusion broth medium. Th e optimum temperature for cadaverine, putrescine, and phenylethylamine form ation was found to be 25 degrees C, as it was for histamine.