Improved growth of Campylobacter pylori in a biphasic system.

The recovery of Campylobacter pylori from clinical specimens is difficult, even when done with an optimal medium, atmosphere, and temperature. The growth of this organism was investigated by comparing a biphasic system with broth culture. The effects of gyration, inoculum, and pH were studied. Brucella agar and broth supplemented with 2.5% fetal bovine serum were used. Growth in the biphasic system was an average of 2 log units (7 X 10(8) versus 5 X 10(6) CFU/ml) greater than that in the broth system (P less than 0.01), and this occurred 12 to 24 h sooner in the biphasic system. When gyration was added, an average of 1 log unit of growth improvement was seen in comparable systems. Improved growth was also seen with low inoculum levels, in which stationary-phase cells in the broth system reached 10(5) CFU/ml compared with 10(7) CFU/ml in the biphasic system. At the three pH ranges studied, growth was best at pH 8 to 9 (6 X 10(9) CFU/ml), averaging 2 log units greater growth than that at pH 6 to 7 and 4 log units greater growth than that at pH 4.5 to 5.5 (P less than 0.01). The improved recovery of the organism for low inoculum levels in a biphasic system may be important for long-term storage and clinical isolation.