In vitro activity of bioactive extracts from rare actinomycetes against multi‐drug resistant Streptococcus pneumoniae

• Published in: Journal of applied microbiology 2015-06, Vol.118 (6), p.1306-1314
• Main Authors: Tiwari, K, Raj, V.S, Upadhyay, D.J, Gupta, R.K
• Format: Article
• Language: English
• Subjects: Actinobacteria - chemistry; Actinobacteria - metabolism; Actinomycetales; Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - metabolism; Anti-Bacterial Agents - pharmacology; anti-infective properties; Antibiotics; antimicrobial susceptibility; bioactive extracts; Community-Acquired Infections - microbiology; culture media; Drug resistance; Drug Resistance, Multiple, Bacterial; genes; Humans; luciferase; mammals; Metabolites; Microbial Sensitivity Tests; Microbiology; minimum inhibitory concentration; multiple drug resistance; multi‐drug resistance; pathogens; pneumonia; rare actinomycetes; ribosomes; S. pneumoniae; Streptococcus; Streptococcus infections; Streptococcus pneumoniae; Streptococcus pneumoniae - drug effects; Streptococcus pneumoniae - growth & development; time‐kill kinetics; translation (genetics)
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1111/jam.12810

AIMS: In this study, we investigated the in vitro potential of the bioactive extracts from five putatively novel species of actinomycetes isolated from the Indian hot desert against multi‐drug resistant (MDR) Streptococcus pneumoniae. METHODS AND RESULTS: The antimicrobial activity of 10 different extracts was evaluated against S. pneumoniae strains with, erm(B) and mef(E) genes as well as fluoroquinolone‐resistant (FQᴿ) strains using the micro‐broth dilution method. Of these 10 extracts, four exhibited good to excellent anti‐S. pneumoniae activity with minimum inhibitory concentrations (MICs) ranging from 0·125 to 8 μg ml⁻¹. The time‐kill kinetics study showed that these extracts killed the pathogens in 2–8 h. In vitro cell‐free transcription/translation of luciferase gene using S30 bacterial extract and TNT mammalian ribosome indicated that they inhibited bacterial ribosomes at much lower concentrations than those required to inhibit the mammalian ribosomes. CONCLUSIONS: This study demonstrates that these are potent concentration‐dependent bactericidal metabolites with 16‐fold higher in vitro activity than levofloxacin against MDR S. pneumoniae. SIGNIFICANCE AND IMPACT OF THE STUDY: Metabolites from actinomycetes can be excellent inhibitors of MDR S. pneumoniae. Considering the in vitro efficacy of these crude extracts against S. pneumoniae MDR spp., once purified these can be used against streptococcal pathogens causing community‐acquired pneumonia.