Antibacterial Activity Against Multidrug-Resistant Clinical Isolates of Nine Plants from Chencha, Southern Ethiopia.

Background: The diminishing efficacy of antibiotics currently in use and the emergence of multidrug-resistant bacteria pose a grave threat to public health worldwide. Hence, new classes of antimicrobials are urgently required, and the search is continuing. Methods: Nine plants were chosen for the current work, which are collected from the highlands of Chencha, Ethiopia. Plant extracts containing secondary metabolites in various organic solvents were checked for antibacterial activity against type culture bacterial pathogens and MDR clinical isolates. The broth dilution technique was used to evaluate the minimum inhibitory and minimum bactericidal concentrations of highly active plant extracts, and time-kill kinetic and cytotoxic assays were performed using the most active plant extract. Results: Two plants (C. asiatica and S. marianum) were highly active against ATCC isolates. The EtOAc extract of C. asiatica produced the highest zone of inhibition ranging between 18.2±0.8-20.7±0.7 and 16.1±0.4-19.2±1.4 mm against Gram-positive and Gram-negative bacteria, respectively. The EtOH extract of S. marianum displayed zones of inhibition in the range of 19.9±1.4-20.5±0.7 mm against the type culture bacteria. The EtOAc extract of C. asiatica effectively curbed the growth of six MDR clinical isolates. The MIC values of C. asiatica against the Gram-negative bacteria tested were 2.5 mg/mL, whereas the corresponding MBC values were 5 mg/mL in each case. The MIC and MBC values were the lowest in the case of Gram-positive bacteria, ie, 0.65 and 1.25 mg/mL, respectively. A time-kill assay showed the inhibition of MRSA at 4 × MIC and 8 × MIC within 2 hours of incubation. The 24 h LD50 values of C. asiatica and S. marianum corresponding to Artemia salina were 3.05 and 2.75 mg/mL, respectively. Conclusion: Overall results substantiate the inclusion of C. asiatica and S. marianum as antibacterial agents in traditional medicines.

Buruli Ulcer and Medical Geo-Microbiology.

Buruli ulcer is a chronic debilitating infectious disease caused by the pathogen Mycobacterium ulcerans, which can be cured if diagnosed and treated in an early stage. However, advanced cases need antibiotic treatment followed by surgical interventions. In this context, an extremely effective and less expensive treatment modality can be developed by means of an extended topical application of certain selected natural clay minerals, most of the time containing illite-smectite having some iron content. There is a scope for developing the speciality, medical geo-microbiology, which is truly a multidisciplinary one, for finding a cure for the severe and advanced cases of BU.

Bioassay-Guided Phytochemical Analyses and Antimicrobial Potentials of the Leaf Extract of Clematis hirsuta Perr. and Guill. Against Some Pathogenic Bacteria and Fungi.

Background: In spite of the great advances in modern medicine in recent decades, medicines of plant origin are still in use for several ailments in different parts of the world. There is always an urge to develop novel, effective and inexpensive antimicrobials. This study was aimed to evaluate the antimicrobial activity and phytochemical composition of the leaf extract of Clematis hirsuta against selected human bacterial and fungal pathogens. Methods: The crude extracts of C. hirsuta leaves were prepared with five different solvents of varying polarity. Agar well diffusion assay on five different species of ATCC organisms, four clinical bacterial isolates, and four clinically isolated fungi were performed. The tube dilution method was used to determine the minimum inhibitory concentrations and the selected extract was subjected to bio-assay-guided fractionation using column chromatography and the active fraction obtained were pooled and GC-MS, FT-IR, and CHN analysis were conducted, and this study is actually bioassay-guided research. Results: A varying patterns of antimicrobial activity against tested microorganism was observed. Acetone extract showed the highest spectrum of activity (17-32mm) in the well diffusion assay against bacteria and 16-23mm in the case of fungi. The MIC ranged from 7.5-60 mg/mL in the case of bacteria and 15-60 mg/mL against fungi. The bioassay-guided column chromatography of the acetone extract followed by GC-MS showed the presence of three major compounds, specifically O-ethylhydroxylamine (43%), 2-ethyl heptanoic acid (20.6%), and 1-nonyl cycloheptane (19.5%). The finding was confirmed by FT-IR and elemental analysis of TLC-separated fractions. Conclusion: The acetone extract showed better antimicrobial activity and the least minimum inhibition concentrations against bacteria compared to fungi. The observed antibacterial can be assigned to the presence of alkoxy amine, alkyl aliphatic acids, and cycloalkane. The overall findings substantiate the traditional usages of the parts of this plant, especially the leaves, in managing infectious diseases.

Chemical Composition, Antioxidant, and Mosquito Larvicidal Activity of Essential Oils from Hyptis capitata Jacq.

Background: Mortality and morbidity associated with vector-borne diseases, particularly those caused by mosquitoes, are increasing and new means of controlling them, including bio-larvicides, are needed. Malaria is a serious threat in many countries of Africa and Asia, and eco-friendly vector preventing measures are very much essential. Plant-derived larvicides are of great importance in this context. Hyptis capitata is an aromatic medicinal plant which is widely distributed in tropical countries. The aim of the present study is to examine the chemical composition, antioxidant and mosquito larvicidal effects of essential oils of this plant, extracted by hydro-distillation. Methods: Chemical compositions of essential oils were analyzed using gas chromatography-mass spectrometry (GC-MS). Antioxidant activity was tested by the 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl (DPPH) assay and the mosquito larvicidal activity was checked against the fourth instar larvae of the malarial vector Anopheles stephensi. Fingerlings of Oreochromis mossambicus were used as a bio-model for toxicity studies. Results: A total of 48 constituents, inclusive of 44 (94.67%) from inflorescence and 19 (97.09%) from leaf oil were identified; δ-cadinene (14.68%) and linalool (6.99%) were the major constituents of the inflorescence oil, while leaf oil contained 1-octen-3-ol (34.08%), methyl linoleate (17.2%), and germacrene D (11.16%). Antioxidant analysis showed an effective concentration (EC50) value of 22.76 µg/mL for leaf oil and 26.18 µg/mL for the inflorescence oil, corresponding to 17.57 µg/mL of ascorbic acid. Both oils showed a respectable larvicidal effect and the lethal concentrations (LC50) are 39.08 µg/mL and 33.19 µg/mL for the inflorescence and leaf oil, respectively. Notably, both the inflorescence and leaf oils are not very toxic to fish with respect to the concentrations tested. Conclusion: This study showed that the essential oils extracted from the leaves and inflorescences of H. capitata are effective antioxidants and can act as inexpensive mosquito larvicidal agents.

Antibacterial Activity of Rosmarinus officinalis against Multidrug-Resistant Clinical Isolates and Meat-Borne Pathogens.

BACKGROUND: In developing countries, the prevalence of bacterial infections is quite rampant due to several factors such as the HIV/AIDS pandemic, lack of hygiene, overcrowding, and resistance to conventional antimicrobials. Hence the use of plant-based antimicrobial agents could provide a low-cost alternative therapy. Rosmarinus officinalis is reputed as a medicinal plant in Ethiopia; however, its antibacterial activity against many of the clinical isolates remains overlooked. METHODS: Tender foliage of R. officinalis was collected and extracted in ethanol (EtOH) and evaluated for their antimicrobial activity against ten multidrug-resistant (MDR) clinical isolates, human type culture pathogens, and meat-borne bacterial isolates by employing agar well diffusion assay. RESULTS: EtOH extract of R. officinalis efficiently subdued the growth of all tested MDR clinical isolates in varying degrees. Salmonella sp. and Staphylococcus aureus were found to be the most sensitive clinical isolates. Likewise, it efficiently repressed the growth of meat-borne pathogens, particularly, S. aureus and Salmonella sp. showing its potentiality to be used as a natural antibacterial agent in the meat processing industry. The mechanism of antibiosis of plant extract against meat-borne pathogens is inferred to be bactericidal. Chemical constituents of the crude plant extract were analysed by Gas Chromatography-Mass Spectroscopy (GC-MS), Fourier Transform Infrared (FT-IR), and UV-visible spectroscopy showing genkwanin (26%), camphor (13%), endo-borneol (13%), alpha-terpineol (12%), and hydroxyhydrocaffeic acid (13%) as the major compounds. CONCLUSION: Overall results of the present study conclude that R. officinalis could be an excellent source of antimicrobial agents for the management of drug-resistant bacteria as well as meat-borne pathogens.

In vitro antibacterial activity of medicinal plants against biofilm-forming methicillin-resistant Staphylococcus aureus: efficacy of Moringa stenopetala and Rosmarinus officinalis extracts.

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) is slowly rising in Ethiopia for the past few decades. Therefore, novel classes of antibiotics are indispensable to combat the increased incidence of newly emerging multidrug-resistant bacteria like MRSA. Terrestrial flora is considered as a reservoir of novel bioactive secondary metabolites as they have provided us with the largest array of natural products. In this background, the present study is intended to evaluate the in-vitro antibacterial efficacy of five medicinal plants (Ocimum lamiifolium Hochst. ex Benth., Rosmarinus officinalis L, Catharanthus roseus Linn., Azadirachta indica A. Juss and Moringa stenopetala Bac) against a panel of seven biofilm-forming MRSA. The leaves of the plants were extracted in organic solvents of varying polarity and the resultant crude extracts of respective medicinal plants were inspected for their antimicrobial activity by well diffusion technique. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of the plant extracts against MRSA were determined by the broth dilution method. Besides, an anti-biofilm assay of the most potent plant extract was also performed, after which its chemical constituents were delineated by combined Gas Chromatographic and Mass Spectroscopic profiling (GC-MS). The results revealed that, of the five plants, three species including M. stenopetala, R. officinalis, and O. lamifolium exhibited significant antibacterial activity. Organic solvents with high and medium polarity were excellent in extracting antimicrobials compared to nonpolar solvents. The broadest and highest rank of activity was observed in the crude ethanolic extract of M. stenopetala. Based on the MIC/MBC ratio, the crude ethanolic extract of M. stenopetala was determined to be bacteriostatic. Anti-biofilm assay showed that the extract of M. stenopetala fairly inhibited the growth of MRSA in the preformed biofilm matrix. The GC-MS analysis of M. stenopetala revealed the presence of twelve compounds with antimicrobial activity. The present study provides new insight into the development of novel drug leads to the management of MRSA.