Razavi Journal of Medicine

Razavi Journal of Medicine

In-Vitro Synergistic Activity of Nortriptyline in Combination with Vancomycin Against a Clinical Vancomycin-Intermediate Staphylococcus aureus (VISA): A Proof-of-Concept Study

Articles in Press

Document Type : Original Article

Authors
Ehsan Momeni 1
Hamid Abtahi 2
Hossein soltani 3
Abbas Alimoradian 4
Mana Shojapour 5
1 Department of Oral Medicine, School of Dentistry, Arak University of Medical Sciences, Arak, Iran
2 Molecular and Medicine Research Center, Arak University of Medical Sciences, Arak. Iran
3 Student Research Committee, Arak University of Medical Sciences, Arak, Iran, School of Dentistry, Arak University of Medical Sciences, Arak, Iran
4 Department of Pharmacology, School of Medicine, Arak University of Medical Sciences, Arak, Iran.
5 Molecular and Medicine Research Center, Arak University of Medical Sciences, Arak. Iran.
10.30483/rjm.2026.254778.1526
Abstract
Background: Staphylococcus aureus is an important pathogen responsible for a wide range of community-and hospital- acquired infections. The increasing prevalence of strains with reduced vancomycin susceptibility has limited therapeutic options. It underscores the need to identify novel antimicrobial combinations.

Objectives: This proof-of-concept study aimed to evaluate the in vitro antibacterial activity of Nortriptyline and to investigate its interaction with vancomycin against a clinical vancomycin- intermediate Staphylococcus aureus (VISA) isolate.

Methods: In this in vitro experimental study, a single clinical VISA isolate was evaluated. The minimum inhibitory concentrations (MICs) of Nortriptyline and vancomycin were determined by broth microdilution. Drug interactions were assessed using the checkerboard assay, and interactions were interpreted based on the fractional inhibitory concentration index (FICI).

Results: The MICs of vancomycin and Nortriptyline alone were 7.81 µg/ml and 1000 µg/ml, respectively. When combined, the MICs of both agents decreased fourfold to 1.95 µg/ml and 250µg/ml respectively. The calculated FICI was 0.5, indicating synergistic activity according to the predefined interpretation criteria.

Conclusion: Nortriptyline exhibited in vitro synergistic activity in combination with vancomycin against a clinical VISA isolate. These preliminary findings provide a rationale for further investigation of this combination in larger collections of clinical isolates and complementary experimental models.
Keywords
Drug repurposing
Antimicrobial resistance
Nortriptyline. Staphylococcus aureus
vancomycin

Acknowledgments: This study was extracted from the professional doctorate thesis of Hossein Soltani, approved by Arak University of Medical Sciences, Arak, Iran. The authors gratefully acknowledge Arak University of Medical Sciences for providing research facilities and financial support (Grant No. 7344).


Availability of data and materials: All data generated or analysed during this study are included in this published article.


Competing Interests: The authors declare that there is no conflict of interest.


Consent for publication: Not applicable.

Ethical Approval: This study was approved by the Ethics Committee of Arak University of Medical Sciences, Arak (Ethical code: IR.ARAKMU.REC.1403.037). All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable


Funding: None.


Authors' Contribution: Conceptualization: H.S and E.M. Data curation: A.A.M. Formal analysis: A.A.M. Investigation: H.S. Methodology: E.M. and H.A. Project administration: H.S. Resources: H.A. Supervision: E.M. and H.A. Validation: E.M., H.A., and A.A.M. Visualization: H.S. and M. Sh. Writing original draft: M. Sh. Writing review and editing: M. Sh.

Open Access Policy: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/

1.     Krismer B, Weidenmaier C, Zipperer A, Peschel A. The commensal lifestyle of Staphylococcus aureus and its interactions with the nasal microbiota. Nature Reviews Microbiology. 2017;15(11):675-87.
https://doi.org/10.1038/nrmicro.2017.104
PMid:29021598
 
2.     Chmielewski M, Załachowska O, Komandera D, Albert A, Wierzbowska M, Kwapisz E, et al. The Oral Cavity-Another Reservoir of Antimicrobial-Resistant Staphylococcus aureus? Antibiotics. 2024;13(7):649.
https://doi.org/10.3390/antibiotics13070649
PMid:39061331 PMCid:PMC11273406
 
3.     Jenkinson HF, Douglas LJ. Interactions between Candida Species and Bacteria in Mixed Infections. Polymicrobial Diseases2002. p. 357-73.
https://doi.org/10.1128/9781555817947.ch18
 
4.     Rehm SJ, Tice A. Staphylococcus aureus: methicillin-susceptible S. aureus to methicillin-resistant S. aureus and vancomycin-resistant S. aureus. Clinical Infectious Diseases. 2010;51(Supplement_2):S176-S82.
https://doi.org/10.1086/653518
PMid:20731575
 
5.     Peacock SJ, Paterson GK. Mechanisms of methicillin resistance in Staphylococcus aureus. Annual review of biochemistry. 2015;84(1):577-601.
https://doi.org/10.1146/annurev-biochem-060614-034516
PMid:26034890
 
6.     Mitevska E, Wong B, Surewaard BG, Jenne CN. The prevalence, risk, and management of methicillin-resistant Staphylococcus aureus infection in diverse populations across Canada: a systematic review. Pathogens. 2021;10(4):393.
https://doi.org/10.3390/pathogens10040393
PMid:33805913 PMCid:PMC8064373
 
7.     Hoseini Zadeh A, Shojapour M, Nazari R, Akbari M, Sofian M, Abtahi H. Genotyping of vancomycin-resistant enterococci in Arak hospitals. Jundishapur J Microbiol. 2015;8(4):e16287.
https://doi.org/10.5812/jjm.8(4)2015.16287
PMid:26034536 PMCid:PMC4449860
 
8.     Liu Y, Tong Z, Shi J, Li R, Upton M, Wang Z. Drug repurposing for next-generation combination therapies against multidrug-resistant bacteria. Theranostics. 2021;11(10):4910-28.
https://doi.org/10.7150/thno.56205
PMid:33754035 PMCid:PMC7978324
9.     Zolotareva D, Zazybin A, Belyankova Y, Bayazit S, Dauletbakov A, Seilkhanov T, et al. Heterocyclic antidepressants with antimicrobial and fungicide activity. Molecules. 2025;30(5):1102.
https://doi.org/10.3390/molecules30051102
PMid:40076325 PMCid:PMC11902072
 
10.  Caldara M, Marmiroli N. Antimicrobial properties of antidepressants and antipsychotics-possibilities and implications. Pharmaceuticals. 2021;14(9):915.
https://doi.org/10.3390/ph14090915
PMid:34577614 PMCid:PMC8470654
 
11.  de Farias Cabral VP, Rodrigues DS, do Amaral Valente Sá LG, Moreira LEA, da Silva CR, de Andrade Neto JB, et al. Analysis of the anti-Candida activity of tricyclic antidepressants in association with amphotericin B and their antifungal mechanisms. Brazilian Journal of Microbiology. 2024;55(4):3617-28.
https://doi.org/10.1007/s42770-024-01459-y
PMid:39198376 PMCid:PMC11711746
 
12.  Rácz B, Spengler G. Repurposing antidepressants and phenothiazine antipsychotics as efflux pump inhibitors in cancer and infectious diseases. Antibiotics. 2023;12(1):137.
https://doi.org/10.3390/antibiotics12010137
PMid:36671340 PMCid:PMC9855052
 
13.  de Farias Cabral VP, Rodrigues DS, do Amaral Valente Sá LG, Moreira LEA, da Silva CR, de Andrade Neto JB, et al. Antibacterial evaluation of tricyclic antidepressants against S. aureus and the possible pathways of the mechanism of action. Pathogens. 2025;14(7):613.
https://doi.org/10.3390/pathogens14070613
PMid:40732661 PMCid:PMC12299878
 
14.  Institute CaLS. Performance standards for antimicrobial susceptibility testing. 32nd ed: Clinical and Laboratory Standards Institute; 2022.
 
15.  Årdal C, Balasegaram M, Laxminarayan R, McAdams D, Outterson K, Rex JH, Sumpradit N. Antibiotic development-economic, regulatory and societal challenges. Nature Reviews Microbiology. 2020;18(5):267-74.
https://doi.org/10.1038/s41579-019-0293-3
PMid:31745330
 
16.  Miethke M, Pieroni M, Weber T, Brönstrup M, Hammann P, Halby L, et al. Towards the sustainable discovery and development of new antibiotics. Nature Reviews Chemistry. 2021;5(10):726-49.
https://doi.org/10.1038/s41570-021-00313-1
PMCid:PMC8374425
 
17.  Zolotareva D, Zazybin A, Belyankova Y, Bayazit S, Dauletbakov A, Seilkhanov T, et al. Heterocyclic Antidepressants with Antimicrobial and Fungicide Activity. Molecules. 2025;30(5).
https://doi.org/10.3390/molecules30051102
PMid:40076325 PMCid:PMC11902072
 
18.  Mandal A, Sinha C, Kumar Jena A, Ghosh S, Samanta A. An Investigation on in vitro and in vivo Antimicrobial Properties of the Antidepressant: Amitriptyline Hydrochloride. Braz J Microbiol. 2010;41(3):635-45.
https://doi.org/10.1590/S1517-83822010000300014
PMid:24031539 PMCid:PMC3768647
 
19.  de S. Machado C, da Rosa TF, Serafin MB, Bottega A, Coelho SS, Foletto VS, et al. In vitro evaluation of the antibacterial activity of amitriptyline and its synergistic effect with ciprofloxacin, sulfamethoxazole-trimethoprim, and colistin as an alternative in drug repositioning. Medicinal Chemistry Research. 2020;29(1):166-77.
https://doi.org/10.1007/s00044-019-02470-x
 
20.  Ugurel E, Turgut-Balik D. Synergistic combination of carvedilol, amlodipine, amitriptyline, and antibiotics as an alternative treatment approach for the susceptible and multidrug-resistant A. baumannii infections via drug repurposing. Eur J Clin Microbiol Infect Dis. 2023;42(9):1063-72.
https://doi.org/10.1007/s10096-023-04634-5
PMid:37428238
 
21.  Wilson TJ, Blackledge MS, Vigueira PA. Resensitization of methicillin-resistant Staphylococcus aureus by amoxapine, an FDA-approved antidepressant. Heliyon. 2018;4(1).
https://doi.org/10.1016/j.heliyon.2017.e00501
PMid:29349359 PMCid:PMC5767979
Razavi Journal of Medicine

Articles in Press, Accepted Manuscript
Available Online from 07 August 2026