Abstract

MARTINEZ HERRERA, D.I et al. EVALUATION OF METHODS FOR THE PRIMARY ISOLATION OF Brucella melitensis IN GOAT MILK. Rev Salud Anim. [online]. 2009, vol.31, n.3, pp. 164-169. ISSN 0253-570X.

In order to evaluate different methods for the primary isolation of Brucella melitensis in goat milk from infected herds, Ver., 45 female adult goats were randomly selected trough the following criteria: 30 previously vaccinated with Brucella melitensis Rev-1 strain, and 15 never vaccinated. Sample size was estimated by a probabilistic model, with unknown population and 35% known prevalence rate (n = 1 - p / pv); where n corresponds to sample size, p for prevalence rate and v variation coefficient (0.05). All goats selected were sampled three times within a 30 day interval to guarantee Brucella spp. milk shedding. Milk samples were aseptically collected into sterile glass tubes from half udder and were refrigerated at 4°C until they were laboratory processed into the next 24 hours. Milk samples were 10,000 X g centrifuged during 20 minutes, in a refrigerated centrifuge at 4^oC. Farrell and Tripticase Soy Agar (TSA) media, were the isolation culture media selected and both were enriched with bovine fresh serum during their formulation. Both isolation culture media selected were inoculated by duplicate with fat and sediment from centrifuged milk as it is established in the Mexican regulations. The results obtained were statistically evaluated by Chi square (c²). A half of both inoculated isolation culture media was incubated under 5 to 10% carbonic dioxide atmosphere and the other half in aerobic one. From 76% of 135 milk samples obtained, only Brucella melitensis biovar - 1 was isolated using both culture media; however, the majority of isolated field strains were recovered from Farrell culture medium (p<0.05); from milk fat 57% of isolated strains and from milk sediment 67%. Also, the best Brucella melitensis biovar - 1 development (p<0.05) from Farrell culture medium was observed by aerobic atmosphere incubation. It is conclusive that Farrell culture medium is more effective than TSA medium for that purpose, both from the fat and sediment of milk, likewise incubation of the samples in aerobic atmosphere was better and there was more successful development of bacteria.

Keywords : Brucella melitensis; isolation; milk; goats.

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