A selective medium for the rapid detection by an impedance technique of Pseudomonas spp. associated with poultry meat.

Abstract

A new medium for detecting and enumerating Pseudomonas spp. associated with poultry meat spoilage by a rapid impedance technique was developed, after testing potential growth promoters for eight Pseudomonas strains and inhibitors against eight competing strains (Enterobacteriaceae) able to grow on the medium of Mead and Adams (1977). Four basal media (brain heart infusion, brucella broth, Shaedler broth and Whitley impedance broth (WIB)) and a synthetic medium were evaluated. Whitley impedance broth was the best basal medium for detecting variations in impedance in relation to Pseudomonas growth. The efficiency of WIB was improved by adding compounds which enhanced the growth of Pseudomonas on the synthetic medium. Among the incubation temperatures tested, 22 degrees C proved to be the best compromise between growth of Pseudomonas associated with poultry meat spoilage and inhibition of competitors. Among the 15 inhibitory substances evaluated against Pseudomonas competitors, five were chosen for inclusion in the final medium: metronidazole, carbenicilline, cetrimide, cycloheximide and diamide (MCCCD medium). Preliminary results obtained from experiments with beef and pork meat showed that this medium could also be used without diamide and at an incubation temperature of 25 degrees C. The impedance technique using MCCCD medium was then compared with an official method which uses the medium of Mead and Adams (1977) on 106 samples of poultry neck skin. The linear regression coefficient between the two techniques was approximately r = 0.85. Impedance was able to detect 10(3) Pseudomonas g-1 within less than 19 h making it a promising technique for predicting poultry meat spoilage.