Antimicrobial activity of some actinomycetes from Western Ghats of Tamil Nadu, India

Peer review under responsibility of Alexandria University Faculty of Medicine.

Available online 4 April 2016

Abstract

Introduction

Microbial diseases are increasing year by year and they are becoming a big threat to public health. There are more than 200 known diseases transmitted by bacteria, fungi, viruses, prions, rickettsia and other microbes to humans. The emergence of drug resistance to chemical drugs is the biggest threat in controlling human pathogens. Hence novel antimicrobial agents from actinomycetes are timely needed for the control of several human pathogens.

Aim

The aim was to find some actinomycetes with antimicrobial metabolites.

Methods

Soil samples were collected from Nilgiris district in Western Ghats of Tamil Nadu, India. Actinomycetes were isolated using serial dilution and plating techniques on actinomycetes isolation agar. Streptomycin and ketoconazole (25 μg/disc) were used as reference controls. The active strains were identified by 16S rRNA and phylogenetic tree was constructed; the sequences were submitted in the GenBank.

Results

Totally 106 actinomycete strains were isolated and cross streaked against various human microbial pathogens. Only 44 (41.50%) exhibited good antimicrobial activity against different pathogenic microbes. Five isolates (FMS-20, TGH-30, TGH-31, TGH-31-1 and IS-4) were chosen for secondary screening using filtrate. Among them FMS-20 filtrate showed good inhibition on the 16th day against all tested microbial pathogens. Further the intracellular methanol extract of FMS-20 showed maximum zone of inhibition against A. brasiliensis (22 mm) at 5 mg/disc. Similarly the extracellular ethyl acetate extract of FMS-20 showed maximum zone of inhibition against B. subtilis (25 mm).

Conclusions

The present work revealed that, among 106 actinomycetes screened, Streptomyces rimosus (FMS-20) (Accession No-KT827106) showed promising antimicrobial activity against all the tested human microbial pathogens.

Keywords:

• Streptomyces rimosus
• Antimicrobial activity
• Disc diffusion
• Zone of inhibition

Acknowledgements

The authors are thankful to Entomology Research institute, Loyola College, Chennai for financial support and facilities. This project was partially financially supported by King Saud University, through Vice Deanship of Research Chairs.

Notes

Peer review under responsibility of Alexandria University Faculty of Medicine.

Available online 4 April 2016