Letters in Drug Design & Discovery, 2009, 6, 63-68 63 1570-1808/09 $55.00+.00 © 2009 Bentham Science Publishers Ltd. Susceptibility of Staphylococcus spp. Isolated from Milk of Goats with Mastitis to Antibiotics and Green Propolis Extracts T.M. Santos Neto 1 , R.A. Mota 1 , L.B.G. Silva 1 , D.A. Viana 2 , J.L. Lima-Filho 3 , L.A. Sarubbo 4 , A. Converti 5 and A.L.F. Porto* ,6 1 Department of Veterinary Medicine, Federal Rural University of Pernambuco, Dois Irmãos, PE, Brazil; 2 Biotechnology Laboratory-LIKA, Federal University of Pernambuco, Recife, PE, Brazil; 3 Department of Biochemistry, Federal University of Pernambuco, Recife, PE, Brazil; 4 Center of Sciences and Technology, Institute of Research in Environment Sciences, Catholic University of Pernambuco, Recife, PE, Brazil; 5 Department of Chemical and Process Engineering, Genoa University, Genoa, Italy; 6 Department of Animal Morphology and Physiology, Federal Rural Uni- versity of Pernambuco, Dois Irmãos, PE, Brazil Received September 19, 2008: Revised November 01, 2008: Accepted November 01, 2008 Abstract: The antimicrobial activity of ethanolic and aqueous extracts of a commercial green propolis and of 13 standard antibiotics was evaluated against Staphylococcus spp. strains isolated from milk of goats with mastitis. More than 95% of the isolates were sensitive to cephalothin and tetracycline, whereas only 28.9% were sensitive to streptomycin. All the iso- lates were susceptible to both ethanolic and aqueous extracts, but the former showed the higher antimicrobial activity. The larger mean diameter of the inhibition zone of coagulase-negative staphylococci (15.5 mm) was in fact obtained with the ethanolic extract. A Minimum Inhibitory Concentration of 50 μg/mL of both extracts was determined, which highlighted a promoting in vitro activity. Keywords: Antimicrobial activity, Goat milk, Mastitis, Green propolis, Staphylococcus spp. INTRODUCTION The nutritional components that make milk an important part of the human diet also support the growth of pathogenic microorganisms coming from milk contamination or from animal infections. Mastitis is the total or partial inflamma- tion of the mammary gland provoked by one or more patho- genic microorganisms, which can appear either in clinical or subclinical forms [1]. The subclinical one is a form of the disease in which there is neither detectable change in the udder nor observable abnormalities in milk. However, the presence of microorganisms in milk usually can be demon- strated by microbial culture, and inflammatory changes in the milk can be detected by special methodologies such as somatic cell count. Staphylococcus spp. are the most fre- quently diagnosed microorganisms responsible for in- tramammary infection in goats and sheeps [2]. In the Brazil Northeast, clinical signs of mastitis in goats were found in 51.5% of the herds [3]. The subclinical masti- tis has a negative impact on the productivity of the herds, reducing by 5 to 20% the milk production [4]. Therefore, in regions where cheese is made from raw milk, controlling clinical and subclinical mastitis becomes a priority. Milk is then heat treated to minimize the risk for human health associated with some mastitis-causing bacteria. Nev- ertheless, even when using pasteurized milk, the ability of some bacteria to produce thermostable toxins enhances the zoonotic role of these pathogens [2]. *Address correspondence to this author at the Department of Animal Mor- phology and Physiology, Federal Rural University of Pernambuco, Av. Dom Manoel de Medeiros s/n, 52171-900 Dois Irmãos, PE, Brazil; Tel: +55 81 2101 2504; Fax: +55 81 2126 8485; E-mail: ana.porto@pesquisador.cnpq.br The use of antibiotics is one of the most commonly used therapies to reduce the intramammary infections caused by pathogens in herds, and the most common reason for treat- ment was mastitis therapy [5]. Several antibiotics are em- ployed in food animals, among others, -lactams, tetracy- clines, aminoglycosides, macrolides, and sulfonamides [5,6]. However, the uncontrolled use of these agents has led to appearance of microbial strains more resistant to classic an- timicrobials [7] along with residual antibiotics in milk that are hazardous to public health and interfere with production of dairy products [8]. To overcome these problems, alternative natural antimi- crobial products are investigated. Among these, propolis has attracted much attention in recent years because of its anti- bacterial, antiviral, antifungal, and antiprotozoal activity [9]. The composition of propolis in terms of relative concentra- tions of its constituents depends on the variety of the honey- bee Apis mellifera as well as the phytogeographic character- istics around the beehive [10]. Propolis composition is ex- tremely complex: its main constituents are beeswax, resin and volatiles, but also pollen, amino acids, flavonoids (major components: rutin, quecertin, galangin) and caffeic acid phenetyl ester were identified, among others [11]. Among the propolis types produced in Brazil, green pro- polis, whose predominant resin components are cinnamic acids, has gained preference in the world propolis market, because it is hard and friable, easily made into powder by mechanical milling and exhales a pleasant resinous odor [11]. Propolis extracts have been reported to strengthen some antibiotic effects, and its antibacterial activity was mainly ascribed to flavonoids or to a synergism between some com- ponents [12]. However, because of the complexity of the mechanism of propolis action, it is difficult to compare it