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The purpose of this paper was to study the etiology of mastitis, determine the antimicrobial susceptibility profile of Staphylococcus spp. and to identify the risk factors associated with infection in dairy cows in the states of Bahia and Pernambuco, Brazil. From the 2,064 milk samples analyzed, 2.6% were associated with cases of clinical mastitis and 28.2% with subclinical mastitis. In the microbiological culture, Staphylococcus spp. (49.1%) and Corynebacterium spp. (35.3%) were the main agents found, followed by Prototheca spp. (4.6%) and Gram negative bacilli (3.6%). In the antimicrobial susceptibility testing, all 218 Staphylococcus spp. were susceptible to rifampicin and the least effective drug was amoxicillin (32.6%). Multidrug resistance to three or more drugs was observed in 65.6% of Staphylococcus spp. The risk factors identified for mastitis were the extensive production system, not providing feed supplements, teat drying process, not disinfecting the teats before and after milking, and inadequate hygiene habits of the milking workers. The presence of multiresistant isolates in bovine milk demonstrates the importance of the choice and appropriate use of antimicrobial agents. Prophylactic and control measures, including teat antisepsis and best practices for achieving hygienic milking should be established in order to prevent new cases of the disease in herds.INDEX TERMS: Staphylococcus spp., multidrug resistance, mammary gland, risk factors.

Introduction: Cnidoscolus quercifolius Pohl (Euphorbiaceae) is a Brazilian medicinal plant, popularly known as "favela", "faveleira" and "urtiga-branca". In folk medicine, its leaves and stem barks are used to treat urinary tract infections. In this study, we report the isolation and characterization of a mixture of two lupane-type triterpenes and one bis-nor-diterpene from the hexane extract of the stem barks. Methods: An aliquot of hexane extract was fractioned by means silica gel chromatography column, yielding a mixture of two compounds (1 and 2). Compound 3 was obtained from the chloroform subfraction through preparative thin layer chromatography (TLC). The compounds were identified by comparison of their spectroscopic data to those reported in the literature. The antibacterial activity of these compounds was evaluated by the microdilution method, through determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), using gram-positive (E. faecalis and S. aureus) and gram-negative (E. coli, K. pneumoniae and S. marcescens) strains. Results: The chemical constituents were identified as a mixture of lupeol-3β-O-cinnamate (1) and lupeol-3β-O-dihydrocinnamate (2) and, phyllacanthone (3). Compounds 1/2 and 3 showed a bacteriostatic effect ten and twenty times higher (MIC = 0.5 and 0.25 mg.ml-1 , respectively) than the hexane extract, respectively (MIC = 5.0 mg.ml-1). The molecules also showed a relevant bactericidal effect, mainly compound 3 (MBC = 0.25 mg.ml-1). Conclusion: These results suggest that C. quercifolius may be considered a promising source of new antibacterial agents. In addition, this investigation supports the medicinal use of this plant for the treatment of urinary tract infections.