metabolites Antibiotics

Actinomycetes are gram-positive bacteria with high guanine + cytosine content of over 55% in their DNA. They belong to the order Actinomycetales and form an important segment of the microflora of most natural environments. Soils, manures and composts, freshwater bodies such as lakes and river bottoms contain an abundance of these organisms. Actinomycetes are aerobic, spore forming organisms with a distinctive feature of possessing filamentous hyphae that do not normally undergo fragmentation. Due to their phenotypic similarities to fungi, actinomycetes are also known as ray fungi (Chaudhary et al., 2013). Actinomycetes provide an excellent resource for the isolation and identification of therapeutically important secondary metabolites such as, antibiotic, antifungal, antiviral, anticancer, enzyme, immunosuppressant and other industrially useful compounds (Dhawane and Zodpe, 2017). These microbial compounds have been a source of life saving environment for many bacterial and fungal infections. Some effective antibiotics manufactured from actinomycetes includes: penicillin, streptomycin, tetracycline, erythromycin, amphotericin and vancomycin. These microbial natural products are notable not only for their potent therapeutic activities but also for the fact that they frequently pose desirable pharmacokinetic properties required for clinical development (Khasabuli and Kibera, 2014). Antibiotics of actinomycetes origin have a wide variety of chemical structure, including aminoglycosides, β-lactams, antracyclines, tetracycline, nucleosides, peptides, polyenes and actinomycins. Secondary metabolites isolated from soil actinomycetes have also been proven to be potent inhibitors of numerous plant pathogens (Agadagba, 2014). 1 A large number of actinomycetes have been isolated and screened from soil in the past several decades, accounting for 70 80% of relevant secondary metabolites available commercially. It has been estimated that approximately one-third of the thousands of naturally occurring antibiotics have been obtained from actinomycetes (Chaudhary et al., 2013). More than 70% of these antibiotics are attributed to two genera viz., Streptomyces and Micromonospora (Rai et al., 2018). The richness and diversity of actinomycetes present in any specific soil, is greatly influenced by the soil type, geographical location, cultivation and organic matter amongst other factors (Agadagba, 2014). According to the World Health Organization, over-prescription and the improper use of antibiotics has led to the generation of antibiotic resistance in many bacterial pathogens (Kumar et al., 2010). Serious infections caused by microorganisms that have acquired resistance to commonly used antibiotics have become a major global healthcare problem in the 21st century (Jarallah and Rahaman, 2014). Some antibiotics like penicillin, erythromycin, and methicillin which used to be very effective treatment against infectious diseases are now less effective because pathogens are now more resistant to such antibiotics. Antibiotic resistant pathogens such as methicillin and vancomycin resistant strains of Staphylococcus aureus and others cause an enormous threat to the treatment of serious infections. These drug resistant strains emerge more quickly than the rate of discovery of new drugs and antibiotics (Kumar et al., 2010). Also, increase in fungal infection happens because the available antifungal drugs are not very effective in treating fungal diseases. Fungal diseases are often difficult to diagnose and treat because antifungal drugs are often not very effective in the setting of impaired immunity (Casadevall et al., 2002). Candida albicans can develop resistance to antimycotic drugs such as fluconazole which is often used to treat candidiasis. The frequency of multiazole-resistant 2 3 strains belonging to Candida species other than Candida albicans is increasing (Hitchcock et al., 1993)