Comparison of atmospheres of incubation for primary isolation of Campylobacter fetus subsp. jejuni from animal specimens: 5% oxygen versus candle jar

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Abstract
An atmosphere with reduced O2 tension is required for the primary isolation of C. fetus ssp. jejuni. Therefore, the use of the conventional atmosphere of 5% O2 and 8% CO2 was compared with the use of a candle jar (17% O2 and 3% CO2) for primary isolation of C. fetus ssp. jejuni from 263 positive canine, cattle and turkey fecal or cecal specimens. At an incubation temperature of 42.degree. C, the atmosphere with 5% O2 resulted in more Campylobacter colonies/plate (P < 0.005) and consistently larger Campylobacter colonies (P < 0.005) than did the candle jar, whereas the growth of interfering bacterial flora was similar. Overall, 96% of the 263 specimens were positive for C. fetus ssp. jejuni with 5% O2; 90% were positive with the candle jar (P < 0.02). More striking differences in isolation rates were seen when both the temperature and the atmosphere were varied: 5% O2 at 42.degree. C enabled recovery of 93% of the isolates from 70 positive specimens, vs. 46% recovery with the candle jar at 37.degree. C. Results with 5% O2 at 37.degree. C were intermediate. The addition of FBP supplement (0.25% each of ferrous sulfate, sodium metabisulfite and sodium pyruvate) to Campy-BAP selective medium made no improvement over unsupplemented medium at 42.degree. C (whether in 5% O2 or in the candle jar), but there was significant improvement over unsupplemented medium when both media were incubated at 37.degree. C in the candle jar. Thus, 5% O2 is apparently superior to the candle jar for primary isolation of C. fetus ssp. jejuni from animal specimens. The interaction of the 2 factors tested (temperature and atmosphere of incubation) evidently greatly decreases isolations rates at 37.degree. C in a candle jar.