Anti-MRSA and β-lactamase inhibition activities from local compost actinomycetes / Puteri Nur Aliah Wan Faizal

Actinomycetes represents the largest group of prokaryotes and known as one of the
largest phyla ubiquitous to both aquatic and terrestrial ecosystems having high G + C
content. Actinomycetes reported to produce beneficial secondary metabolites such as
an immunosuppressive agent, antitumor agent, vitamins, herbicides and pesticides.
They are well known producers of antibiotics and more than 70% of antibiotics are
obtained mainly from Streptomyces. Unfortunately, the efficacy of these life-saving
antibiotics is significantly threatened by the spreading of drug resistance pathogens,
making the treatment ineffective and can lead to death. β-lactamase inhibitors have
been identified as an emerging potential in overcoming the resistance towards β-lactam
antibiotics. The aims of this study are to evaluate the growth ability of actinomycetes
isolates on four different types of selective media, to screen the anti-MRSA activity of
actinomycetes isolates using resazurin microtiter-based assay, to determine the
inhibition properties of extracts towards β–lactamase resistance mechanism and also to
identify and characterize isolates with the best inhibitor properties based on 16S rRNA
gene sequence. The growth study of 165 isolates demonstrated that the majority of the
isolates (80%) grew on ISP 2 due to its nutrient compositions compared to ISP 3
(10.3%) and ISP 7 (9.7%). However, only 85 bioactive compounds were successfully
obtained for further anti-MRA and screening for β–lactamase inhibition activity. The
three highest yield of the crude obtained were 0.11%, 0.10% and 0.09%. It was found
that isolate C2B6 produced the highest percentage of anti-MRSA activity (16.45%)
while the highest inhibition percentage obtained was 71.02% extracted from isolate
G3C38. From molecular analysis using 16S rRNA, C2B6 was mostly related to
Streptomyces cavournesis and G3C38 was 99.36% similar to Streptomyces
griseorubens.