Determination of histamine in mahi-mahi fillets (coryphaena hippurus) implicated in a foodborne poisoning

Abstract

An incident of foodborne poisoning causing illness in 53 victims due to ingestion of fish fillets occurred in January, 2009, in Kaohsiung city, southern Taiwan. The two suspected fish samples contained 11.3 and 37.7 mg/100 g of histamine, which is greater than the 5.0 mg/100 g allowable limit suggested by the United States Food and Drug Administration. Given the allergy-like symptoms of the victims and the high histamine content in the suspected fish samples, this foodborne poisoning was strongly suspected to be caused by histamine intoxication. Five histamine-producing bacterial strains capable of producing 1.23 to 36.48 ppm of histamine in trypticase soy broth (TSB) supplemented with 1.0% L-histidine (TSBH) were identified as Bacillus subtilis (four strains) and Enterobacter aerogenes (one strain) by 16S rDNA sequencing with polymerase chain reaction (PCR) amplification. Moreover, the fish species of suspected samples were identified as mahi-mahi (Coryphaena hippurus) by using PCR direct sequence analysis. Based on the finding that high contents of histamine (>30 mg/100 g) were detected in the suspected mahi-mahi samples, we speculate the temperature abuse of the fillets before cooking contributed to the presence of high histamine levels in mahi-mahi fillets and resulted in foodborne poisoning. Although histamine-producing strains, Bacillus subtilis and Enterobacter aerogenes, were isolated from suspected fish samples, they might not be the main contributors to histamine accumulation because of low histamine production. These results re-emphasize proper handling temperature for seafoods and offer an important awareness that Coryphaena hippurus fillets could become a hazardous food item in causing histamine poisoning even though no quality deficiency was observed on the fillets.