Abstract

Resistance of pathogens to common veterinary antibiotics hampers mastitis treatment and motivates the discovery of new antimicrobials. In this study, extracts from two aquatic plants, Salvinia auriculata and Hydrocleys nymphoides, were assayed against bovine mastitis pathogens. Selected parts of plants were extracted with different solvents. The extracts showed activity only against the Gram-positive strains tested and the largest inhibition zones were seen for hexane extracts. The minimum inhibitory concentration values ranged from 0.2 to 1.0 mg/ml. Growth ofStreptococcus agalactiae in the presence of different extracts with concentrations below MIC reduced the number of CFU/ml by more than 90%. Sub-MIC concentrations of the hexane extracts prepared from roots of S. auriculata inhibited approximately 50% of biofilm formation. Greater reduction was achieved for ethanol extract prepared from leaves of H. nymphoides. We concluded that these aquatic plants are potential sources for the investigation of new antimicrobial compounds.

Key words: Staphylococcus aureus, Streptococcus agalactiae, aquatic plants,Salvinia auriculata, Hydrocleys nymphoides, antimicrobial activity.

Abbreviation

HRSA, Extract prepared in hexane from roots of Salvinia auriculata; DRSA, extract prepared in dichloromethane from roots of S. auriculata;ARSA, extract prepared in ethyl acetate from roots of S. auriculata; ERSA, extract prepared in ethanol from roots of S. auriculata; HLSA, extract prepared in hexane from leaves of S. auriculata; DLSA, extract prepared in dichloromethane from leaves of S. auriculata; ALSA, extract prepared in ethyl acetate from leaves of S. auriculata; ELSA, extract prepared in ethanol from leaves of S. auriculata; HLHN,extract prepared in hexane from leaves of Hydrocleys nymphoides; DLHN, extract prepared in dichloromethane from leaves of H. nymphoides; ALHN, extract prepared in ethyl acetate from leaves of H. nymphoides; ELHN, extract prepared in ethanol from leaves of H. nymphoides.