Effect of Storage Temperature and Sample Volume on Brucella melitensis Isolation from Goat Milk
Jennifer A. Zambriski *
Cornell University, Department of Animal Science, Ithaca, NY 14853, U.S.A
Ryan C. Maves
Naval Medical Research Unit SIX, Avenida Venezuela Cuadra 36 s/n, Callao 02, Peru
Daryl V. Nydam
Cornell University, Veterinary Medical Center, Room C2 562, Ithaca, NY 14853, U.S.A
Viterbo Ayvar
Centro de Salud Global UPCH, Tumbes, Panamericana Norte Km 1275, Puerto el Cura – Tumbes, Peru
David Cepeda
Naval Medical Research Unit SIX, Avenida Venezuela Cuadra 36 s/n, Callao 02, Peru
Rosa Castillo
Naval Medical Research Unit SIX, Avenida Venezuela Cuadra 36 s/n, Callao 02, Peru
Andre Díaz-Pino
Centro de Salud Global UPCH, Tumbes, Panamericana Norte Km 1275, Puerto el Cura – Tumbes, Peru
Mayuko Saito
AsociaciÏŒn Benéfica PRISMA, Carlos Gonzales 251, Urb. Maranga, San Miguel, Lima, 32, Peru
Robert H. Gilman
Johns Hopkins University, Bloomberg School of Public Health, 615 N Wolfe St. Rm W5515, Baltimore, MD 21205, U.S.A
*Author to whom correspondence should be addressed.
Abstract
Aim: To determine the impact of storage temperature and sample volume on milk culture success under a simulated field setting.
Study Design: Prospective cohort study.
Place and Duration of Study: Centro de Salud Global UPCH, Tumbes, Peru and Naval Medical Research Unit SIX, Lima, Peru. April, May and June 2010.
Methodology: We aseptically collected milk from unvaccinated goats, and then experimentally inoculated the pooled milk sample with B. melintensis in order to compare the effect of two different sample volumes (2ml and 5ml) and two different storage temperatures (4ºC and -20ºC) on culture success.
Results: We achieved higher culture success in refrigerated (4ºC) versus frozen (-20ºC) samples (OR 4, 95% CI 1.7, 9.6) and with 5-ml versus 2-ml aliquots (OR 9, 95% CI 3.3, 26.6).
Conclusion: In resource-poor field settings where cold-chain and transportation are unreliable, use of ice for sample storage and transport of goat milk is an acceptable method for the purpose of culturing B. melintensis.
Keywords: Brucellosis, goat, peru, milk, culture, refrigeration, freeze, storage