To establish an enrichment system of high efficiency for recovery of Campylobacter jejuni from market chickens, the effects of the temperature, duration of incubation, and pH of the enrichment culture on the isolation of the bacterium were evaluated. Whole chickens or chicken parts in plastic bags were individually rinsed, and the washings filtered through cheesecloth. The cells were separated from the washings by centrifugation, and the pellet was inoculated into 100 mL of enrichment broth. Isolation of C. jejuni from poultry samples was significantly increased by incubating these samples in an enrichment medium at 42 degrees C as opposed to 35 degrees C; for 48 h as opposed to 24 h or 72 h; and at pH 7.0 as opposed to pH 6.0, 6.5, 7.5, or 8.0.

The coagulase reaction of Staphylococcus aureus on the PPSA (pork plasma for S. aureus) agar of Devoyod et al. was found to be fibrinogen-deficient. By including bovine fibrinogen (BFG) in the medium, the fibrin halos around S. aureus colonies became more distinct, preparations of pork plasma previously unacceptable for inclusion in the original PPSA agar were performing well, and the amount of pork plasma required in PPSA agar could be reduced by nearly 90%. In the modified medium, designated PPF (pork plasma fibrinogen) agar, the agar base (Baird-Parker agar without egg yolk) was unchanged. After surface plating, the base was covered with 8 mL of a modified overpour agar: 2.5% pork plasma, 0.38% BFG, and 0.0015% soy trypsin inhibitor in 0.7% Bacto agar. Most S. aureus strains could be enumerated after 24 h of incubation at 35 degrees C; the others required 44 h. Without soy trypsin inhibitor, a number of strains showed considerable fibrinolysis between 24 and 44 h of growth; this activity was neutralized by the inhibitor. The S. aureus counts of 27 food samples on PPF agar were essentially the same as the confirmed S. aureus counts obtained by the Baird-Parker method.