Background:

Corynebacterium bovis is the species among the Corynebacterium spp. more often isolated from mammary glands and despite being classified as a secondary pathogen, its role in intramammary infection is not yet defined. Some studies have shown that this agent causes no change in production and milk composition, while others noted the ability of Corynebacterium sp. in causing mastitis, considering it as a limiting factor for production of quality milk. This study aims were to determine the prevalence of Corynebacterium sp. in herds of five Brazilian States and assess the risk factors associated with the presence of this agent in milk samples. It was also analyzed the influence of Corynebacterium sp. on the California Mastitis Test of each cow in the dairy herds in Santa Catarina State (SC), Brazil. Materials, Methods &

Results:

It was conducted a longitudinal study in dairy herds in the States of Pernambuco (PE), Minas Gerais (MG), Paraná (PR), Santa Catarina (SC) and Rio Grande do Sul (RS). Herds were sampled four times in the period from January 2010 to July 2011, at six months intervals. Milk samples were collected from each animal, composed of the mixture of the four mammary quarters, packed in ice and sent to laboratories responsible for each State for microbiological analysis. Bacteria examination was performed by inoculation 10 µL of each milk sample, using a calibrated disposable loop on blood Agar plates with 5% sheep blood and incubated at 37ºC for 24 - 48 h. The microorganisms were identified following the recomendations of National Mastitis Council (NMC). From the total of 4949 milk samples, 666 (13,46%) were positive for Corynebacterium sp. The results of bacterial isolation and identification, and questionnaire data from herds in the States of Minas Gerais (MG), Pernambuco (PE), Paraná (PR) and Rio Grande do Sul (RS) were sent to the CAV/UDESC - Lages, SC. A questionnaire was applied to the farmers for information on management practices for milking and mastitis control including questions about foremilk stripping, washing and drying udders before milking, teat disinfection before and after milking, and treatment of clinical cases and of dry cows. Only in herds from Santa Catarina State California Mastitis Test (CMT) was performed in the milk of animals sampled as an indirect measure of somatic cell count (SCC). The prevalence of Corynebacterium sp. in herds from Minas Gerais State showed a significant higher difference in relation to the herds in other States, with a percentage of isolation of 21,07%.

Discussion:

Although Corynebacterium sp. is considered a secondary pathogen, the isolation of this agent was comparable to the observed for Staphylococcus aureus and Streptococcus agalactiae, which are considered major pathogens. Corynebacterium sp. was isolated in all dairy herds of Minas Gerais and Pernambuco States. The risk factors evaluated through the questionnaire showed no significant influence on the isolation of Corynebacterium sp. of milk samples from herds in all five States. The isolation of Corynebacterium sp. was related to changes in California Mastitis Test of milk samples from herds in Santa Catarina State, not only in the number of positive mammary quarters, but also in the California Mastitis Test score.