Conductance method for quantitative determination of Photobacterium phosphoreum in fish products

This paper presents the development of a sensitive and selective conductance method for quantitative determination of Photobacterium phosphoreum in fresh fish. A calibration curve with a correlation coefficient of −0.981 was established from conductance detection times (DT) for estimation of cell levels. Less than 50 cells g⁻¹ of fish could be detected in less than 45 h. The selectivity of the method in relation to other Photobacteria or other bacteria isolated from spoiled fish was good. DTs for 10–100 cfu ml⁻¹ of P. phosphoreum were shorter than DTs for 10⁶ cells ml⁻¹ of the other organisms tested. In naturally contaminated fresh fish, P. phosphoreum was specifically enumerated when it made up 0.1% of the total level of micro-organisms. The repeatability (S.D.%) of the conductance assay ranged from 2.9% to 7.3%.