Antibacterial activity of Lantana camara L. against multidrug resistant pathogens from ICU patients of a teaching hospital

The scientific basis for the use of the common shrub-weed plant Lantana camara L. was investigated by testing leaf extracts for antibacterial activity. Dried leaf powders were extracted using a hot-solvent extraction method with eight polar to non-polar solvents in succession. Crude extracts were tested for antibacterial activity against three multidrug-resistant (MDR) Gram-positive bacteria: methicillin-resistant Staphylococcus aureus (MRSA), Streptococcus pyogenes, and vancomycin-resistant Enterococcus faecalis (VRE); and five MDR extended-spectrum β-lactamase-producing Gram-negative bacteria: Acinetobacter baumannii, Citrobacter freundii, Proteus mirabilis, Proteus vulgaris and Pseudomonas aeruginosa. The MRSA strain was resistant to 16 of 18 antibiotics, while Streptococcus pyogenes and VRE were resistant to 15 of 18 antibiotics. Similarly, A. baumannii and P. aeruginosa were resistant to 14 of 16 antibiotics. It was found that plant extracts with petroleum ether and water had the least antibacterial activity. Leaf extracts with dichloromethane and methanol registered the highest antibacterial activity on all bacterial strains. The minimum inhibitory concentration and minimum bactericidal concentration of two active leaf extracts, obtained with dichloromethane and methanol were determined. Phytochemical analysis of dichloromethane leaf extracts confirmed the presence of alkaloids, glycosides, terpenoids, saponins, flavonoids, and steroids, but reducing sugars were also absent; and, in the methanolic leaf extract, alkaloids, terpenoids, saponins, flavonoids and steroids were present, but glycosides, reducing sugars and tannins were absent. These findings point to the potential of the plant as a probable source of bioactive compounds and provide a scientific basis for its folklore/ethnomedicinal uses for infectious diseases.