Serial‐Passage Assessment Shows No Confirmed Resistance Development to Norway Spruce (Picea Abies) Resin in Bacterial Species Relevant to Wound Infection
- 1Repolar Pharmaceuticals Ltd. Espoo Finland
- 2Department of Bioproducts and Biosystems School of Chemical Engineering, Aalto University Espoo Finland
Abstract
The search for antimicrobials with a low propensity to select resistance has intensified in response to the global antimicrobial resistance crisis. Norway spruce resin (Picea abies) has long been used in Northern European wound care traditions and has shown broad antimicrobial activity in earlier microbiological studies. In the present study, we evaluated whether prolonged exposure to medical‐grade spruce resin promotes reduced susceptibility in reference strains of three bacterial species relevant to wound infection. A 20‐day serial‐passage experiment was performed with Staphylococcus aureus, Pseudomonas aeruginosa, and Enterococcus faecalis using sub‐inhibitory resin concentrations and broth microdilution readouts at baseline, Day 10, and Day 20. Resistance development was predefined as a ≥ 4‐fold increase in inhibitory concentration. Baseline inhibitory concentrations were 1.25% for S. aureus, 5.0% for P. aeruginosa, and 2.5% for E. faecalis. After 20 days, inhibitory concentrations were 2.5%, 10.0%, and 2.5%, respectively, corresponding to at most twofold changes and remaining below the predefined threshold for resistance development. Validation and vehicle‐control arms indicated that these shifts were not attributable to medium transfer or solvent‐related bias. These findings suggest that medical‐grade Norway spruce resin has a low short‐term tendency to select for reduced susceptibility under serial‐passage conditions.
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BibTeX
@article{yamileva2026serialpassage,
title = {{Serial‐Passage Assessment Shows No Confirmed Resistance Development to Norway Spruce (Picea Abies) Resin in Bacterial Species Relevant to Wound Infection}},
author = {Kamilla Yamileva and Simone Parrotta and Maryam Ghanbarirad and Evgen Multia},
journal = {MicrobiologyOpen},
year = {2026},
month = oct,
doi = {10.1002/mbo3.70436},
url = {https://doi.org/10.1002/mbo3.70436},
note = {CC BY},
}
RIS
TY - JOUR
TI - Serial‐Passage Assessment Shows No Confirmed Resistance Development to Norway Spruce (Picea Abies) Resin in Bacterial Species Relevant to Wound Infection
AU - Kamilla Yamileva
AU - Simone Parrotta
AU - Maryam Ghanbarirad
AU - Evgen Multia
PY - 2026
DA - 2026/10/27
JO - MicrobiologyOpen
DO - 10.1002/mbo3.70436
UR - https://doi.org/10.1002/mbo3.70436
AB - The search for antimicrobials with a low propensity to select resistance has intensified in response to the global antimicrobial resistance crisis. Norway spruce resin (Picea abies) has long been used in Northern European wound care traditions and has shown broad antimicrobial activity in earlier microbiological studies. In the present study, we evaluated whether prolonged exposure to medical‐grade spruce resin promotes reduced susceptibility in reference strains of three bacterial species relevant to wound infection. A 20‐day serial‐passage experiment was performed with Staphylococcus aureus, Pseudomonas aeruginosa, and Enterococcus faecalis using sub‐inhibitory resin concentrations and broth microdilution readouts at baseline, Day 10, and Day 20. Resistance development was predefined as a ≥ 4‐fold increase in inhibitory concentration. Baseline inhibitory concentrations were 1.25% for S. aureus, 5.0% for P. aeruginosa, and 2.5% for E. faecalis. After 20 days, inhibitory concentrations were 2.5%, 10.0%, and 2.5%, respectively, corresponding to at most twofold changes and remaining below the predefined threshold for resistance development. Validation and vehicle‐control arms indicated that these shifts were not attributable to medium transfer or solvent‐related bias. These findings suggest that medical‐grade Norway spruce resin has a low short‐term tendency to select for reduced susceptibility under serial‐passage conditions.
SN - 2045-8827
ER -