- Scombroid poisoning, caused by histamine intoxication, is one of the most prevalent illnesses associated with seafood consumption in the United States. The illness is usually accompanied with a variety of symptoms, such as rash, nausea, diarrhea, flushing, sweating, and headache. Incidence of scombroid poisoning has been consistently reported in the U.S. through surveillance and is often underestimated due to mild and transient symptoms.
Histamine can be formed in fish through enzymatic decarboxylation of histidine. Many bacteria include Morganella morganii, Proteus vulgaris, Klebsiella pneumoniae, and Enterobacter aerogenes are known to be prolific histamine formers and have been frequently isolated from fish. Among them, Morganella morganii is the most prolific histamine former and plays the major role in histamine formation in fish that is improperly handled. The U.S. Food and Drug Administration's seafood regulations limit histamine in fish at a level of 5 mg/100g (50 ppm) for assuring the safe consumption of fish.
This study was conducted to determine growth of histamine-producing bacteria (Enterobacter aerogenes, Enterobacter cloacae, Proteus hauseri, Morganella morganii, and Klebsiella pneumoniae) and histamine formation in yellowfin tuna (Thunnus albacares) stored at 5, 15 and 25°C as well as effects of treatments of electrolyzed oxidizing (EO) water and in ice form on reducing histamine-producing bacteria on food contact surfaces (ceramic tile and stainless steel) and fish skin (Atlantic salmon and yellowfin tuna).
Enterobacter aerogenes and Morganella morganii were the most prolific histamine formers capable of producing >1,000 ppm of histamine in broth culture after 12 h at 25°C. Both species grew rapidly at elevated temperatures (15-25°C), but the growth was inhibited at 5°C. Histamine was produced by the bacteria in medium broth and tuna meat held at 15 and 25°C when bacterial populations increased to ≥10⁶ CFU/ml (or CFU/g). However, storing yellowfin tuna inoculated with M. morganii or E. aerogenes at 5°C resulted in slight decreases of the bacteria over 14 days of storage and no histamine formation. Low-temperature (≤5°C) storage was critical to prevent histamine formation in fish.
Enterobacter aerogenes and Morganella morganii could survive well on food contact surfaces (glazed ceramic tile and stainless steel) and fish skin. However, a treatment of electrolyzed oxidizing (EO) water (50 ppm chlorine) for 5 min was capable of removing the bacteria completely from the surfaces (>1.7 to >5.4 log CFU/cm² reductions). Soaking salmon skin in EO water containing 100 ppm for 120 min could reduce E. aerogenes and M. morganii on salmon skin by 1.3 and 2.2 log CFU/cm², respectively. Holding fish skin in EO ice containing 100 ppm of chlorine for 24 h could reduce E. aerogenes by 1.6 log CFU/cm² on salmon skin and 2.4 log CFU/cm² on tuna skin and M. morganii by 2.0 log CFU/cm² on salmon skin and 3.5 log CFU/cm² on tuna skin.
EO water can be used as a sanitizer for decontaminating histamine-producing bacteria on food contact surfaces. Holding fish in EO ice (100 ppm chlorine) could be used as a post-harvest treatment to reduce histamine-producing bacteria contamination on fish skin and decrease probability of histamine formation in fish during storage.