Abstract
In effort to identify novel bacterial agents, this study was initiated to evaluate the antimicrobial properties of 17 crude extracts from 12 medicinal plants against beta-lactam-resistant bacteria. The antimicrobial activities of plant extracts were evaluated against clinically proved beta-lactam-resistant bacteria (Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, Serratia marcescens, Acinetobacter baumannii, Staphylococcus aureus and Enterococcus sp.) and reference strains of bacteria (Escherichia coli ATCC 35218, Enterobacter aerogenes ATCC 29751, E. aerogenes ATCC 13048, Pseudomonas aeruginosa ATCC 27853 and Enterococcus hirae ATCC 9790) by using disc-diffusion and agar-dilution assays. The crude plant extracts demonstrated broad spectrum activity against all bacteria tested with inhibition zones in the range of 8-30 mm. The minimal inhibitory concentration (MIC) values of different plant extracts against the tested bacteria were found to range from <or= 0.3 to >or= 10 mg ml(-1). The most active plant extracts were from Dortenia picta and Bridelia micrantha (MIC: 1.25-10 mg ml(-1)) on beta-lactam-resistant Gram-negative bacilli and the extracts from B. micrantha, Mallotus oppositifolius, Garcinia lucida, Garcinia. kola, Campylospermum densiflorum (leaves) and C. zenkeri (root) on beta-lactam-resistant Gram-positive cocci (MIC: <or= 0.3-5 mg ml(-1)). Of the 17 plant extracts studied, seven showed good antimicrobial activity against the tested bacteria. The stem bark of B. micrantha and the leaves of D. picta were most active towards beta-lactamase producing Gram-negative bacilli. This study shows that medicinal plants could be sources of compounds which can be used to fight against beta-lactam resistant bacteria.
Highlights
Antimicrobial-resistant bacteria are the causes of numerous clinical problems worldwide
In an ongoing programme of research and development of traditional medicine in Cameroon focused on the screening of traditionally used Cameroonian plants for antimicrobial properties, we have reported antibacterial activities on Gram positive bacteria [10], and beta-lactamase inhibitory properties of some plant extracts [11]
The antimicrobial activity of crude extracts from these plants against bacteria (Gram-negative bacilli and Gram-positive cocci) resistant to betalactam antibiotics examined in the present study was assessed qualitatively by measuring the inhibition zone diameters and quantitatively by determining minimal inhibitory concentrations
Summary
Antimicrobial-resistant bacteria are the causes of numerous clinical problems worldwide. More than fifty products were developed, exhibiting sometimes expanded spectra of action, low toxicity and in many cases, reasonable cost. Resistance to this antibiotic family can be attributed to several factors. More than 500 betalactamases have been described (http:// www.lahey.org/studies/ consulted on February 20, 2008) and divided into four molecular classes: A, B, C and D [3] In effort to identify novel bacterial agents, this study was initiated to evaluate the antimicrobial properties of 17 crude extracts from 12 medicinal plants against beta-lactam-resistant bacteria. Conclusion: Of the 17 plant extracts studied, seven showed good antimicrobial activity against the tested bacteria. This study shows that medicinal plants could be sources of compounds which can be used to fight against beta-lactam resistant bacteria
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