Assessment of gelatin-supplemented BACTEC blood culture medium in a pediatric hospital.

Sodium polyanetheolesulfonate (SPS), an anticoagulant used in blood culture media, adversely affects the isolation of Neisseria meningitidis. The addition of gelatin appears to counteract this effect. Studies using the radiometric BACTEC system, however, have noted a lower isolation rate of other bacteria from gelatin-supplemented media. We wished to evaluate the effect of the addition of gelatin (1.2%) to a nonradiometric BACTEC aerobic medium (NR6A) on the recovery of N. meningitidis and other pathogens. The NR6A medium with gelatin (NR6A analogue) also contained a lower concentration of SPS (0.025% vs 0.035%). We did 6045 paired comparisons of blood cultured in routine NR6A medium and the NR6A analogue. Eight isolates of N. meningitidis were recovered, five only from the gelatin-supplemented medium and three from both bottles. There was no statistically significant difference in total recovery of aerobic and facultative bacteria or Candida species from both bottles. Haemophilus influenzae was detected earlier in the nonsupplemented NR6A medium. We conclude that the use of the NR6A analogue medium appeared to increase the yield of N. meningitidis without adversely affecting the recovery of other common pathogens, although the recovery of H. influenzae was slightly delayed.