Background: The antimicrobial resistance crisis clearly highlights the need for novel antimicrobial agents from novel sources. With this in view, we selected a sub-set of 254 microorganisms from novel natural product sources and screened extracts of these for antimicrobial activity. All selected fungi and extremophiles have not been reported to exhibit antimicrobial properties. Methods: Natural source microorganisms were grown in the appropriate culture conditions and cultures were extracted with ethyl acetate, resuspended in DMSO and diluted for biological testing. They were tested against clinical bacterial and yeast isolates using broth microdilution and MIC, was determined. Extracts of selected microorganisms were fractionated by reversed phase C18 solid phase extraction (SPE) using increasing concentration of aqueous methanol. Results: Of the 254 microorganisms screened, 22 exhibited interesting antimicrobial properties though no significant activity against Gram-negative pathogens was observed. Of these, seven were further selected for extract fractionation and tested against a larger set of isolates where sufficient quantities permitted. The effect of the extracts on bacteria and yeasts are summarized in the table below. The summary data is shown in the Table. Two selected extracts (PK and EP) were fractionated by SPE and tested on a subset of pathogens. The activity was identified in specific isolated fraction for both strains with increased activity compared to the crude extracts though PK lost its specificity and showed some activity against yeasts. Conclusions: The current screening campaign yielded several interesting extracts that exhibited diverse antimicrobial activities. While it wasn’t possible to test all extracts against all pathogens due to limited material, the data to date show that several of the extracts exhibited promising anti-Gram-positive activity and two had activity against yeasts. A first round of fractionation was successfully conducted for two extracts. Overall, the results to date support further investigation of the extracts and elucidation of the pure active chemical entities
Activity of Extracts from Novel Natural Product Sources Against Clinically Relevant Human Pathogens
Giovanna Cristina Varese;Federica Spina;Iolanda Perugini;
2022-01-01
Abstract
Background: The antimicrobial resistance crisis clearly highlights the need for novel antimicrobial agents from novel sources. With this in view, we selected a sub-set of 254 microorganisms from novel natural product sources and screened extracts of these for antimicrobial activity. All selected fungi and extremophiles have not been reported to exhibit antimicrobial properties. Methods: Natural source microorganisms were grown in the appropriate culture conditions and cultures were extracted with ethyl acetate, resuspended in DMSO and diluted for biological testing. They were tested against clinical bacterial and yeast isolates using broth microdilution and MIC, was determined. Extracts of selected microorganisms were fractionated by reversed phase C18 solid phase extraction (SPE) using increasing concentration of aqueous methanol. Results: Of the 254 microorganisms screened, 22 exhibited interesting antimicrobial properties though no significant activity against Gram-negative pathogens was observed. Of these, seven were further selected for extract fractionation and tested against a larger set of isolates where sufficient quantities permitted. The effect of the extracts on bacteria and yeasts are summarized in the table below. The summary data is shown in the Table. Two selected extracts (PK and EP) were fractionated by SPE and tested on a subset of pathogens. The activity was identified in specific isolated fraction for both strains with increased activity compared to the crude extracts though PK lost its specificity and showed some activity against yeasts. Conclusions: The current screening campaign yielded several interesting extracts that exhibited diverse antimicrobial activities. While it wasn’t possible to test all extracts against all pathogens due to limited material, the data to date show that several of the extracts exhibited promising anti-Gram-positive activity and two had activity against yeasts. A first round of fractionation was successfully conducted for two extracts. Overall, the results to date support further investigation of the extracts and elucidation of the pure active chemical entities
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