Use of Dorset egg medium for maintenance and transport of Neisseria meningitidis and Haemophilus influenzae type b.

Studies of bacterial meningitis are hampered by the inability to maintain the viability of etiological agents during transport to reference laboratories. The long-term survival rate of 20 isolates of Neisseria meningitidis and Haemophilus influenzae type b (Hib) on Dorset egg medium, supplemented Columbia agar base medium, chocolate agar, and Amies medium was compared with that on 70% GC agar (chocolate) transport medium. N. meningitidis isolates were also inoculated onto 5% horse blood agar, and Hib was inoculated onto Haemophilus test medium. All of the N. meningitidis isolates remained viable on Dorset egg medium for 21 days; viability on the other media was poor after only 7 days. Recovery rates of Hib isolates were similar on Dorset egg and Haemophilus test media (100% after 21 days) and significantly better than on the other media. Dorset egg medium is inexpensive and easy to make and may be invaluable for studies of bacterial meningitis in developing countries.