Antimicrobial activity of selected plant species from "the Argentine Puna" against sensitive and multi-resistant bacteria

Abstract

Aim: The plant species reported here are traditionally used in the "Puna" or "Altiplano" of Argentina for ailments related to bacterial infections. The aim of this study was to evaluate their antimicrobial properties against a panel of sensitive and multi-resistant Gram-positive and Gram-negative bacteria. Materials and methods: The antimicrobial activity of tinctures and aqueous extracts (Baccharis boliviensis, Chiliotrichiopsis keidelii, Chuquiraga atacamensis, Fabiana bryoides, Fabiana densa, Fabiana punensis, Frankenia triandra, Parastrephia lucida, Parastrephia lepidophylla, Parastrephia phyliciformis, Tetraglochin cristatum) was determined using the agar macrodilution and broth microdilution methods recommended by the Clinical and Laboratory Standards Institute (CLSI, formerly NCCLS). The antibiotic resistant clinical strains were isolated from nosocomial infection in human lesions of skin and soft parts. Results: The ethanolic extracts of 11 plant species inhibited the growth of one or more of the following strains: Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Enterobacter cloacae, Morganella morganii, Pseudomonas aeruginosa. Ethanol extracts (tinctures) of aerial parts of Baccharis, Fabiana and Parastrephia showed the highest levels of antibacterial activity on methicillin, oxacillin and gentamicin resistant Staphylococcus with MIC values from 20 to 150 μg/ml. Baccharis boliviensis and Fabiana bryoides were more active than the other plant species on Enterococcus faecalis with different phenotype. The most interesting activity on multi-resistant Gram-negative strains was obtained from Chuquiraga atacamensis. Parastrephia species showed activity against Enterobacter cloacae, Pseudomonas aeruginosa and Proteus mirabilis. The ethanolic extracts exhibited stronger activity and broader spectrum of action than aqueous extracts. The extracts were bactericidal in most cases. Conclusions: The presence of antibacterial activity in Puna plant extracts against multi-resistant bacteria give support to their traditional use for treating conditions associated with microorganisms in humans and animals and consequently seems promising for the treatment of multi-resistant bacteria.