The antibacterial effects of propolis are more concentrated when used in an ethanol extract and should be incorporated into the cattle's treatment protocol. What's odd is that they didn't apply the EEP directly on the cows udder but chose to go "downstream" and treat the milk...
Bactericidal
Activity of Ethanolic Extracts of Propolis Against Staphylococcus aureus
Isolated from Mastitic Cows
World JMicrobiol Biotechnol, 2012 Feb 28
Staphylococcus
aureus is an important pathogen for both humans and animals, and it has been an
ubiquitous etiological agent of bovine mastitis in dairy farms worldwide.
Elimination
of S. aureus with classic antibiotics is difficult, and the current study aimed
to evaluate the efficacy of ethanolic extracts of propolis (EEP) against S.
aureus cultivated in complex media or milk. EEP (0-0.5 mg ml(-1)) decreased
growth of S. aureus in BHI media and 1 mg ml(-1) was bactericidal against
washed cell suspensions (10(7) CFU ml(-1)). Propolis extracts also killed S.
aureus cells resuspended in milk, but the bactericidal dose was at least
20-fold greater. Cultures that were transferred for at least 60 generations
with sub-lethal doses of propolis did not change much their sensibility to EEP.
Atomic force microscopy images revealed changes in morphology and cell size of
S. aureus cells exposed to EEP (0.5 mg ml(-1)).
Our results
indicate that propolis extracts might be effective against mastitis-causing S.
aureus strains in vivo, but milk constituents affect the inhibitory activity of
propolis.
Considering
that propolis-resistance appears to be a phenotype not easily selected, the use
of EEP combined or not with other antimicrobial agents might be useful for
mastitis control in vivo.












