Formulation of improved media for isolation and cultivation of Campylobacter fetus
Campylobacter fetus, a microaerophilic, Gram-negative rod, is a well-known cause of contagious abortion and infertility in cattle and sheep and is gaining increasing recognition as an opportunistic human pathogen. In the past, the unusual oxygen requirements of the organism have complicated its recovery from clinical sources; optimum recovery necessitates the use of special gas mixtures, vacuum pumps, etc., not routinely used in most laboratories. In this study, the stimulatory effects of compounds found to enhance aerotolerance and growth of C. fetus were tested for 62 strains of C. fetus, representing each subspecies, to test the desirability of supplementing conventional media with these additives. Brucella agar supplemented with 0.025% (each) FeS04Â·7H20, sodium bisulfite, and pyruvic acid (FBPA agar) supported growth of 82% of the strains tested under simulated candle jar condtions. Brucella broth supplemented with 0.2% FeS04 Â·7H20, 0.025% sodium bisulfite, and 0.050% pyruvic acid (FBPB broth) supported growth of 61 of 62 strains at 21% 02, 2.5% CO2 with static incubation.
Therefore, FBPA agar and FBPB broth are recommended for the isolation and cultivation of C. fetus. Although isolation from clinical sources is still dictated to some extent by the oxygen tension used for cultivation, improved recovery may be expected regardless of equipment or facilities available. Another compound found to enhance aerotolerance of C. fetus was SOD. This finding supports the hypothesis that the stimulatory effect of the media additives results from a direct action on the culture medium by degrading toxic derivatives of oxygen, such as the superoxide radical and hydrogen peroxide.