Mursamacin: a novel class of antibiotics from soil-dwelling roundworms of Central Kenya that inhibits methicillin-resistant Staphylococcus aureus

Abstract

Antibiotic-resistant bacteria, also called "superbugs", can at worst retrogress modern medicine to an era where even sore throats resulted in death. A solution is the development of novel types of antibiotics from untapped natural sources. Yet, no new class of antibiotic has been developed in clinical medicine in the last 30 years. Here, bacteria from insect-killing Steinernema roundworms found in the soils of Central Kenya were isolated and subjected to specific molecular identification. These were then assayed for production of antibiotic compounds with potential to treat methicillin-resistant Staphylococcus aureus infections. The bacteria were identified as Xenorhabdus griffiniae and produced cell free supernatants that inhibited S. aureus. Fermenting the bacteria for 4 days yielded a heat stable anti-staphylococcal class of compounds that at low concentrations also inhibited methicillin-resistant S. aureus. This class contained two major compounds whose identity remains unknown. Thus X. griffinae isolated from Steinernema roundworms in Kenya have antimicrobial potential and may herald novel and newly sourced potential medicines for treatment of the world's most prevalent antibiotic resistant bacteria.

Draft genomes, phylogenomic reconstruction and comparative genome analysis of three Xenorhabdus strains isolated from soil-dwelling nematodes in Kenya

“…BMMCB and XN45 were both described as X. griffiniae species [20, 32]. We previously demonstrated XN45 and X.…”

“…These were above the same species thresholds of 98.65, 97 and 97 % respectively [11, 50]. Conversely, strains BMMCB and XN45 were not conspecific, as demonstrated by their respective percentage nucleotide similarities values of 98.545, 93.67 and 92.066 % for 16S rRNA, recA and serC genes respectively [20]. Indeed, BMMCB was not an X.…”

“…"The indirect isolation of Xenorhabdusbacteria from haemolymph was based on a previously described method (Boemare & Akhurst, 2006) with modifications (Awori et al,2017). " S3.Accessions numbers, strains and predicted gene counts of genomes used in phylogenomic and pangenomic analyses.…”

“…In Kenya, apart from X. hominickii from Steinernema karii [13], and X. griffiniae XN45 that we isolated from Steinernema sp. scarpo [20],…”

Nematophilic bacteria associated with entomopathogenic nematodes and drug development of their biomolecules

“…strain BMMCB was described as an Xenorhabdus. griffiniae species ( Mothupi et al, 2015 ), but we ( Awori et al, 2017 ) demonstrated that its nucleotide identities values for the recombinase A ( recA ), phosphoserine transferase ( serC ), and small subunit ribosomal ribonucleic acid (rRNA) (SSU) genes, with those of the type species, were below the accepted threshold for conspecific strains—97% for protein-coding genes ( Tailliez et al, 2010 ) and 98.7% for SSU gene ( Kim et al, 2014 ).…”