Diluents and the Enumeration of Stressed Campylobacter jejuni

Significant discrepancies in calculated counts of Campylobacter jejuni strains ATCC 33250 and 29428 were observed between undiluted samples and samples diluted in 0.1% peptone water when cultures had been incubated at 42°C under micro-aerobic conditions in brucella broth containing 2% NaCl. The influence of 0.1% peptone water, brucella broth and phosphate buffer as diluents for enumeration of C. jejuni stored at 6 and -18°C in brucella broth with 0.5 and 2% NaCl was studied. The three diluents were equally effective for the recovery of C. jejuni from refrigerated broth containing 0.5% NaCl. However, when the organism had been refrigerated in the broth with 2% NaCl or frozen in the broth with either level of salt, dilution with brucella broth produced significantly higher counts than dilution with 0.1% peptone water or phosphate buffer.