Abstract
Bacterial infections are responsible for a large number of deaths every year worldwide. On average, 80% of the African population cannot afford conventional drugs. Moreover, many synthetic antibiotics are associated with side effects and progressive increase in antimicrobial resistance. Currently, there is growing interest in discovering new antibacterial agents from ethnomedicinal plants. About 60% of the population living in developing countries depends on herbal drugs for healthcare needs. This study involved the screening of Centella asiatica commonly used by herbal medicine practitioners in Kisii County to treat symptoms related to bacterial infections. Standard bioassay methods were applied throughout the study. They included preliminary screening of dichloromethane: methanolic extract of Centella asiatica against human pathogenic bacteria including Salmonella typhi ATCC 19430, Escherichia coli ATCC 25922, Shigella sonnei ATCC 25931, Bacillus subtilis ATCC 21332, and Staphylococcus aureus ATCC 25923 using agar disc diffusion, broth microdilution method, and time-kill kinetics with tetracycline as a positive control. Phytochemical screening was carried out to determine the different classes of compounds in the crude extracts. Data were analyzed using one way ANOVA and means separated by Tukey's test. Dichloromethane: methanolic extract of Centella asiatica was screened against the selected bacterial strains. Time-kill kinetic studies of the extracts showed dose- and time-dependent kinetics of antibacterial properties. Phytochemical screening of the DCM-MeOH extract revealed the presence of alkaloids, flavonoids, phenolics, terpenoids, cardiac glycosides, saponins, steroids, and tannins. The present study indicates that the tested plant can be an important source of antibacterial agents and recommends that the active phytoconstituents be isolated, identified, and screened individually for activities and also subjected further for in vivo and toxicological studies.
Highlights
IntroductionInfectious diseases are a major cause of morbidity and mortality worldwide [1,2,3]. e use of antibiotics to control these diseases has led to the emergence of antibiotic-resistant pathogens and, the need for alternative medicines [4, 5], such as medicinal plants [6], which are available, affordable, and efficacious with minimal side effects [7, 8].e problem of antibiotic resistance is confounded by the emergence of “superbugs” such as Staphylococcus aureus, Mycobacterium tuberculosis, Enterobacter species, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa that are resistant to multiple classes of antibiotics [9, 10].In addition, many bacterial pathogens form biofilms when they come in contact with a hydrated surface [11]. e biofilms are extracellular matrices that enclose aggregates of bacterial cells on surfaces [11, 12] and are a major problem in e Scientific World Journal clinical therapeutics since microbial communities adhered to surfaces are physiologically distinct from planktonic cells of the same bacteria [13]. e formation of bacterial biofilms has been shown to increase resistance to antibiotics by up to 1000-fold [14]
E problem of antibiotic resistance is confounded by the emergence of “superbugs” such as Staphylococcus aureus, Mycobacterium tuberculosis, Enterobacter species, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa that are resistant to multiple classes of antibiotics [9, 10]
Tetracycline (30 μg) was used as a positive control, and 0.2% DMSO was used as a negative control. e antibacterial effects of the reference drug were significantly higher against the five bacterial species compared with the C. asiatica extract at all concentrations tested (p < 0.05; Table 1). e inhibitory activities of the C. asiatica extract concentration of 500 mg/ ml were significantly higher against the five bacterial species tested compared to the other extract concentrations tested (p < 0.05; Table 1). e same trend was observed when C. asiatica extracts were tested at 250 mg/ml and 125 mg/ml
Summary
Infectious diseases are a major cause of morbidity and mortality worldwide [1,2,3]. e use of antibiotics to control these diseases has led to the emergence of antibiotic-resistant pathogens and, the need for alternative medicines [4, 5], such as medicinal plants [6], which are available, affordable, and efficacious with minimal side effects [7, 8].e problem of antibiotic resistance is confounded by the emergence of “superbugs” such as Staphylococcus aureus, Mycobacterium tuberculosis, Enterobacter species, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa that are resistant to multiple classes of antibiotics [9, 10].In addition, many bacterial pathogens form biofilms when they come in contact with a hydrated surface [11]. e biofilms are extracellular matrices that enclose aggregates of bacterial cells on surfaces [11, 12] and are a major problem in e Scientific World Journal clinical therapeutics since microbial communities adhered to surfaces are physiologically distinct from planktonic cells of the same bacteria [13]. e formation of bacterial biofilms has been shown to increase resistance to antibiotics by up to 1000-fold [14]. E use of antibiotics to control these diseases has led to the emergence of antibiotic-resistant pathogens and, the need for alternative medicines [4, 5], such as medicinal plants [6], which are available, affordable, and efficacious with minimal side effects [7, 8]. E biofilms are extracellular matrices that enclose aggregates of bacterial cells on surfaces [11, 12] and are a major problem in e Scientific World Journal clinical therapeutics since microbial communities adhered to surfaces are physiologically distinct from planktonic cells of the same bacteria [13]. About 80% of the population living in developing countries uses medicinal plants for their health care needs due to their inability to maintain a steady supply of conventional medicines [7, 16]. Herbal drugs are used in combination with conventional drugs if the patient feels that the prescribed medicines are ineffective [17]
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