Bovine mastitis is an inflammatory response of the udder, caused mainly by colonization by microbial pathogens. The susceptibility of cows to mastitis is affected by some factors, including the cow’s age, genetic traits, and stage of lactation and nutrition (Sordillo, 2005). This disease has been associated with different levels of economic losses in dairy cattle in different countries. Argentina has been classified as the 17th main milk-producer country in the world (Tiwari et al., 2013). However, in this country, mastitis is still a serious problem, causing more than $0.99/cow/day economic losses for farmers (Vissio et al., 2015). This scenario is worryingly higher than the previously published average economic losses assessed by farmers (Huijps et al., 2008).
Currently, antibiotic therapy is the most common treatment of bovine mastitis-infected dairy cows. However, some of the serious problems associated with this therapy include the low cure rate, the bacterial resistance and the presence of antimicrobial residues in milk (Gomes and Henriques, 2016). A recently evaluated strategy to substitute the administration of cox 2 inhibitor is the use of natural compounds produced by bacteria. The use of microbiota from healthy organisms has previously shown interesting results in both animals and humans (Bouchard et al., 2015; Iwase et al., 2010).
Coagulase-negative staphylococci (CNS) are a group of bacteria classified as either minor mastitis pathogens or commensal microbiota. Until recently, it was difficult to draw consistent conclusions about the relevance of CNS in bovine udder health. Some studies considered CNS as true mastitis pathogens, although most were retrieved from subclinical mastitis cases (Pyörälä and Taponen, 2009), whereas others considered CNS to be commensal bacteria with limited or absent negative effects on SCC, milk quality, and milk production (De Vliegher et al., 2012). It has been previously recognized that CNS play an important role in the establishment of the cow’s microbiome, suggesting specific antibacterial activities in competition against pathogenic strains (Braem et al., 2014).
Biofilms have been proposed as an important virulence factor, involved in the development and maintenance of intramammary infections (Gomes et al., 2016). A biofilm is defined as a sessile microbial community where cells are adhered to a biotic or abiotic surface and embedded in a protective extracellular matrix. The biofilm lifestyle seems to play an important role during bacterial infection, providing defense against the host immune system and resistance to antimicrobial treatment (de la Fuente-Núñez et al., 2013; Scherr et al., 2014). Antibiotic therapies for biofilm-associated infections usually require high doses for prolonged times and they often fail (Wu et al., 2014). Thus, the development and discovery of new anti-biofilm agents is currently an urgent demand for clinical practice. Anti-biofilm compounds may act in prevention treatments by blocking biofilm formation or disrupting the microbial community within a biofilm (Ribeiro et al., 2016). Several microorganisms produce and release different compounds to combat pathogenic bacterial biofilms, including molecules that interfere with bacterial communication and signaling and enzymes capable of degrading the extracellular matrix components. An important feature of these microorganisms is their non-microbicidal mechanism of action, not placing an evolutionary pressure to develop bacterial resistance (Blackledge et al., 2013).
Materials and methods
Mastitis is considered the most relevant pathology in lactating cows and responsible for major economic losses in the dairy industry worldwide (Melchior et al., 2006). In Argentina, mastitis control has been significantly improved in the last years, but sub-clinical mastitis is still a serious problem (Vissio et al., 2015). The dairy farm studied was in accordance with this feature, because a high prevalence of sub-clinically infected quarters was confirmed. The identification of the bacterial isolates revealed results similar to previous reports, with CNS and S. aureus as the most relevant groups of minor and major mastitis–associated pathogens respectively (Dieser et al., 2013).