Antibacterial resistance modulatory properties of selected medicinal plants from Ghana

Abstract

Bacterial resistance to antibiotics is a serious challenge to human and animal health and all efforts are being put together to resolve the menace. In this study the antibiotic resistance modifying activity of ten plants was established by determination of the minimum inhibitory concentrations (MICs) of the plant extracts, the MICs of the antibiotics alone (amoxicillin, ciprofloxacin, erythromycin and tetracycline) and the MICs of the antibiotics in the presence of sub-inhibitory concentrations of the methanol extracts of some selected medicinal plants including Clerodendron splendens, Cyperus esculentus, Duranta plumieri, Kigelia africana, Kyllinga brevifolia, Momordica charantia, Phyllanthus amarus, Pycnanthus angolensis, Secamone afzelii and Thuja occidentalis against two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gramnegative bacteria (Escherichia coli and Pseudomonas aeruginosa). The extracts were found to possess varying degree of antimicrobial activity with MICs between 4 and 50 mg/mL. It was observed that 26.9% of the plant extract-antibiotic combinations/interactions resulted in the reduction of activity of antibiotics. Almost 17% of the extract-antibiotic interactions led to the complete loss of activity of the antibiotics and 30.0% of the extract-antibiotic combinations resulted in resistance modulation. Three per cent of the extract-antibiotic combinations/interactions had antibiotics that were not active when used alone but became active in the presence of the extracts and 23.1% extract-antibiotic combinations/interactions had no modifying effect on the individual in vitro activities of the antibiotics. There is need to isolate the bioactive agents from the extracts especially those that potentiated the activity of the antibiotics.

Alternatives to conventional antibiotics for the prevention and treatment of commonly occurring diseases in feedlot cattle

“…24 Unrefined or refined plant extracts can also interact with existing antimicrobials and these interactions can be negative, indifferent, or positive, with potentiation of some otherwise ineffective conventional antibiotics. 25,26 The European Food Safety Authority has published guidelines for the "Animal Health Risk Assessment of multiple chemicals in essential oils for farm animals". 27 However, to prevent adverse outcomes and to ensure efficacy, it would be reasonable to require the same standards to apply to plant extracts as apply to conventional therapeutics.…”

“…In addition to local cytotoxic effects, plant products and plant extracts must also be evaluated for more generalised toxicity, 23 as shown by the hepatorenal toxicity found in rats fed Lablab purpureus seeds 24 . Unrefined or refined plant extracts can also interact with existing antimicrobials and these interactions can be negative, indifferent, or positive, with potentiation of some otherwise ineffective conventional antibiotics 25,26 …”

Antimicrobial Potential of Extract from a Pseudomonas aeruginosa Isolate

“…The overuse of antibiotics has put bacteria under long-term selective pressure, resulting in antibiotic resistance, which means the bacteria will be tough to kill. Antibiotic resistance genes (ARGs) are the key functional elements in antibiotic-resistant bacteria and they can move between microbes via horizontal gene transfer [ 4 , 5 ].…”

“…The broad-spectrum beta-lactamase (ESBL) enzymes found in Enterobacteriaceae have also aggravated the global antibiotic-resistance menace. These ESBL enzymes hydrolyze and inactivate beta-lactam antibiotics such as cephalosporins and also enhance microbial resistance to quinolones, aminoglycosides, and sulfonamides leading to the emergence of multidrug resistance (MDR) [ 5 ].…”

“…This menace has therefore necessitated the search for more potent metabolites from microorganisms that can be developed into antibiotics as treatment options for resistant bacteria infections [ 5 ]. Streptomyces , Bacillus, Cephalosporium, and Penicillium which are known producers of antibiotics are being studied for antibiotics production globally [ 6 , 7 ].…”