Photobacterium phosphoreum caused a histamine fish poisoning incident

Area of Science:

• Food Safety
• Microbiology
• Toxicology

Background:

• Histamine fish poisoning (HFP) is a foodborne illness linked to scombroid fish consumption.
• Previous HFP cases have implicated bacteria such as Morganella morganii, Raoultella planticola, and Hafnia alvei.
• The specific bacterial cause in sporadic HFP incidents, particularly involving dried fish, requires further investigation.

Purpose of the Study:

• To identify the causative agent of a histamine fish poisoning (HFP) incident linked to dried sardines (iwashi maruboshi).
• To characterize the histamine-producing capabilities of the isolated bacterial strain.
• To determine the role of Photobacterium phosphoreum in HFP.

Main Methods:

• Isolation and identification of histamine-producing bacteria from contaminated iwashi maruboshi.
• Biochemical characterization and partial 16S rDNA sequencing for bacterial identification.
• Histamine production assays at different temperatures and in fish homogenates.

Main Results:

• A histamine-producing bacterial strain, YS4-7, was isolated from iwashi maruboshi containing 1700 mg/kg histamine.
• Strain YS4-7 was identified as Photobacterium phosphoreum.
• P. phosphoreum YS4-7 demonstrated significant histamine production, exceeding that of Morganella morganii at lower temperatures (4 and 12°C).
• The strain produced 546 mg/kg histamine in sardine homogenate after 12 hours at 20°C.

Conclusions:

• Photobacterium phosphoreum was identified as the causative bacterium in a sporadic histamine fish poisoning (HFP) case linked to dried sardines.
• This study marks the first report of P. phosphoreum as the responsible agent in an HFP incident.
• The findings highlight the potential of P. phosphoreum to cause HFP, especially under specific storage conditions.