Natural toxins: Poisoning of domestic animal in Italy – 2016 annual report

Abstract

Bovine mastitis, a disease caused by inflammation of the udder, is one of the major causes of global dairy industry losses. Alternative therapies such as ethnoveterinary medicine are worthy of further study since mastitis-causing bacterial pathogens are becoming increasingly resistant to conventional antibiotic therapy. Plant species were selected on the basis of their known antibacterial activity, use in ethnoveterinary medicine and their ready availability for in vitro testing against a panel of bacterial species implicated in causing mastitis (both ATCC strains and clinical isolates). Water and acetone extracts were prepared from various plant parts of Acacia nilotica, Tetradenia riparia, Aloe arborescens and Crassula multicava. Antimicrobial activity was determined using a serial microdilution assay and cytotoxicity was evaluated against a mammalian kidney cell line using a tetrazolium-based colorimetric assay.A. arborescens and C. multicava were not generally active against the tested bacteria. Acetone extracts of A. nilotica bark and T. riparia flower extracts were most active against Gram-positive bacteria. Activity against Gram-negative species, notably Proteus vulgaris and Enterobacter aerogenes, was also recorded with MIC values as low as 0.0195 mg/ml. The best selectivity index (SI) value of 4.22 was obtained by the T. riparia flower acetone extract against the field strain of Streptococcus uberis. Although a degree of toxicity to mammalian cells was noted in most of the extracts, SI values above 1 indicate that antibacterial activity was greater than cellular toxicity for some extracts, a preliminary indication of safety. These extracts, or purified active compounds derived from them, may prove useful in further investigations of alternative mastitis treatments.