Bactericidal Activity of Ethanolic Extracts of Propolis
Against Staphylococcus aureus Isolated from Mastitic Cows
World J Microbiol Biotechnol, 2012 Feb;28(2):485-91. Epub
2011 Jul 17.
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.
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