Antimicrobial activity of bovine beta-lactoglobulin

CHANETON L; PÉREZ SÁEZ JM; BUSSMANN LE

JOURNAL OF DAIRY SCIENCE

AMER DAIRY SCIENCE ASSOC-ADSA

Año: 2011 vol. 94 p. 138 - 145

0022-0302

Bovine mastitis is one of the most economically deleterious diseases affecting dairy herds. It results from the infection of the udder by pathogenic microorganisms such us Staphylococcus aureus, Streptococcus uberis and Escherichia coli. The mammary gland is capable of preventing and combating bacterial infection by means of a complex network of innate and adaptive immune mechanisms. Lactoferrin (LF) is an 86 kDa protein that presents antibacterial activity and apparently plays a relevant role in mammary gland defense against infection. â-lactoglobulin (â-LG) is a 18 kDa protein present in most mammal species but notably absent in humans, rodents and lagomorphs. There are different genetic variants of this protein, being â-LG A and â-LG B the most frequent. In spite of being a profoundly studied protein, the biological function of â-LG is not thoroughly understood and, most noticeably, there are no reports on the possible effects of the native protein on bacterial growth. Hence, the objective of this paper was to analyze a potential antibacterial activity of â-LG against mastitis agents. To accomplish this objective we purified â-LG from normal bovine milk by a mild non-denaturing method and performed in vitro growth inhibition assays with Staph. aureus, E. coli and Strep. uberis. Our results show that â-LG is capable of inhibiting growth of Staph. aureus and Strep. uberis, but has no effect on E. coli. The antimicrobial activity against Staph. aureus and Strep. uberis followed a concentration dependent pattern. This antimicrobial activity was elicited by the intact protein, since Tricine-SDS-PAGE and analytical gel filtration chromatography did not reveal the presence of short degradation peptides. Analysis of antimicrobial activity of the different genetic variants of â-LG showed that â-LG A present higher inhibitory activity against Staph. aureus and Strep. uberis compared to â-LG B. Co-incubation of â-LG and LF resulted in a significant augmented antibacterial activity against Staph. aureus, suggesting that both proteins may act in a additive fashion. This fact, together with the observation that both proteins present a complementary spectrum of action suggests that â-LG and LF may complement each other in the mammary gland defense against bacterial infection.