Extreme environments like subterranean caves are promising natural sources of antibiotic-producing microorganisms. As the prevalence of multiple drug- and extremely resistant pathogenic microorganisms increases globally, a continuous need for a new pool of defense through the bioactive secondary metabolites produced by bacteria such as Streptomyces spp. is essential. The assessment of the microbial diversity of Philippines caves is not popular among local scientists due to the physical risks involved and the very limited information available that will verify the existence of important species. Our studies however proved otherwise. Philippine limestone caves proved to be good sources of potentially new, biologically active microorganisms with potential socio-economic and medical importance. This research initiative is under the umbrella research program of the UPLB Museum of Natural History on Cave Biodiversity. Our team pioneered the study on cave microbial diversity and continues to discover new species and records of microorganisms with food, medical, agricultural and industrial applications.

Our team, initiated studies on the microbial diversity of caves found in Polillo Islands, Quezon with the support from the UPLB Basic Research Program. We also isolated new records of biofilm-forming and lactic acid bacteria and filamentous fungi from caves in Panay Islands; Cavinti, Laguna; Atimonan, Quezon, Biak-na-Bato, Bulacan; Boac, Marinduque and Cacupangan, Pangasinan funded by the UPLB MNH Core funds. The metagenome of bat guano collected from Mabini, Pangasinan was determined through a combination of Next Generation Sequencing using Illumina and bioinformatic analyses (De Leon et al., 2018). This pioneering research was funded by the DA-BAR/UP NSRI Post-Doctoral Research Fellowship and in collaboration with the Korean Collection for Type Cultures. Novel species and new record of Streptomyces spp., an actinobacterium, isolated from the same cave proved the abundance of potential Streptomyces spp. From bat guano (De Leon et al., 2018). These are kept in store in the UPLB MNH Microbial Culture Collections.

These interesting discoveries led us to further this research through this proposal that aims to screen the Streptomyces spp. isolated from bat guano of Cabalyorisa Cave, Mabini, Pangasinan for antimicrobial properties against selected multiple drug resistant (MDR) pathogenic bacteria. This will be done through screening of the Streptomyces spp. isolated from the bat guano of Cabalyorisa Cave, Mabini, Pangasinan for antibacterial activity against drug-resistant (DRB) and drug-susceptible bacteria (DSB) such as Mycobacterium tuberculosis, Klebsiella pneumoniae, Staphylococcus aureus, Salmonella spp., Enterobacter spp., Enterococcus spp. and Escherichia coli. The Streptomyces spp. isolated from Cabalyorisa Cave have been identified phenotypically and genotypically and validated to be new records and new species of Streptomyces.

All the Streptomyces spp. will be screened for antibiotic production against resistant and susceptible pathogenic bacteria (clinical isolates and reference strains) available at the Dr. Pablo O. Torre Sr. Memorial Hospital TB Culture Center (DPOTSMH-TBCC). This antibacterial assay will be done at DPOTSMH-TBCC by a DOH-accredited and certified TB Technologist. Antibacterial assay will follow the recommended protocol by the Department of Health Drug Susceptibility Testing (DOH DST). Further phenotypic and genotypic characterizations using conventional morpho-cultural, rapid biochemical and molecular characterization (16S rRNA sequencing) will be done to identify the putative strains of MDR Mycobacterium tuberculosis (MDR-TB) with susceptibility against the Streptomyces filtrates. Phenotypic and genotypic characterization will be done in the UPLB MNH Microbial Culture Collection and at the Korean Collection of Type Cultures for validation of new species. The bioactive secondary metabolites of selected high activity strains of Streptomyces will be profiled using the Ultra Performance Liquid Chromatography in the UPLB Institute of Chemistry.

This is the first time that a study will screen Streptomyces spp. isolated and identified from bat guano of Philippine cave. In 2014, Nordenfjäll of Swedish University of Agricultural Sciences published a similar study on microorganisms isolated from several soil and plant samples including a sample of bat guano from the Philippines and were screened for antimicrobial activity against Staphylococcus spp. and Pseudomonas spp. Aside from this report, there were no related or similar studies of such kind reported or published in the country.

This proposal will initially focus on screening the Streptomyces spp. from bat guano of Mabini, Pangasinan for antibacterial activity against DRB and DSB. The success of this study will be used to other known multiple drug resistant (MDR) pathogenic bacteria and fungi in future research projects. This will provide sustainable and cheaper natural sources of antibiotic that can provide a new line of defense for DRB such as the multiple drug resistant (MDR), extensively drug resistant (XDR) and pandrug resistant (PDR) in the near future.