Caspian Journal of Veterinary Sciences

Caspian Journal of Veterinary Sciences

Antibacterial and antibiofilm effects of α-pinene on carbapenem-resistant Klebsiella pneumoniae: modulation of adhesion-related virulence genes

Articles in Press

Document Type : Original Article

Authors
Hoda Ghoraba 1
Fatemeh Ashrafi 1
Rezvan Mousavi Nadushan 2
Hosein Abbaspour 3
1 Department of Microbiology, NT.C., Islamic Azad University, Tehran, Iran.
2 Department of Food Science and Technology, NT.C., Islamic Azad University, Tehran, Iran.
3 Department of Biology, NT.C., Islamic Azad University, Tehran, Iran.
10.22034/cjvs.2026.579761.1062
Abstract
Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a major cause of healthcare-associated infections with high mortality, largely due to biofilm formation and expression of adhesion-associated genes such as mrkA, mrkD, and fimA. Natural monoterpenes such as α-pinene (PIN) have emerged as potential alternative antimicrobial agents. This study evaluated the antibacterial and antibiofilm effects of PIN against CRKP clinical isolates and investigated its impact on biofilm-related gene expression. CRKP isolates were identified from clinical specimens and screened for mrkA, mrkD, and fimA. The minimum inhibitory concentration (MIC) of PIN was determined using broth microdilution. Time-kill kinetics were assessed at subMIC levels. Antibiofilm activity was evaluated using the crystal violet assay. Gene expression changes following subMIC exposure were analyzed via quantitative real‑time PCR (qRT-PCR). Among 89 K. pneumoniae isolates, 23 (25.8%) were carbapenem-resistant. MIC values of PIN ranged from 125–250 µg/ml. SubMIC concentrations caused minimal direct bactericidal activity but significantly reduced biofilm biomass (p < 0.001). PIN significantly downregulated mrkD in most isolates, while mrkA and fimA showed isolate-dependent reductions (p < 0.05). α-Pinene demonstrated significant antibiofilm activity against CRKP, primarily through modulation of fimbrial adhesion gene expression rather than strong bactericidal action. These findings support its potential as an antivirulence adjunctive therapy.
Keywords
α-Pinene, Bacterial resistance, Klebsiella pneumoniae, Biofilm, Natural products
Subjects
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Caspian Journal of Veterinary Sciences

Articles in Press, Accepted Manuscript
Available Online from 10 November 2026

  • Receive Date 27 April 2026
  • Revise Date 15 June 2026
  • Accept Date 15 June 2026