Synergistic Activity of Three Iranian Medicinal Plants in Combination with Ceftazidime and Neomycin against Bacterial Strains Causing Nosocomial Infections

Document Type : Original paper


1 Department of Toxicology and Pharmacology, Faculty of Pharmacy and Pharmaceutical Sciences Research Center, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.

2 Department of Pharmaceutics, Faculty of Pharmacy, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.

3 Department of Pharmacogenosy, Faculty of Pharmacy and Herbal Medicine Research Centre, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.


Background and objectives: This study aimed to investigate the antimicrobial properties of Salvia limbata, Centella asiatica, and Bacopa Monnieri extracts against Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus (MRSA). We also examined the synergistic effect of these extracts with ceftazidime and neomycin. The antimicrobial effects of these plants had been reported before but synergistic effect with broad spectrum antibiotics such as ceftazidime and neomycin was an important issue that we tried to determine. Methods: Methanol extracts were prepared by percolation method and phenolics content was determined by Folin–Ciocalteu method. The minimum inhibitory concentrations (MIC) of the extracts were determined by the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method. Checkerboard assay was used to evaluate the synergistic effect of the extracts with ceftazidime and neomycin. Results: Salvia limbata methanolic extract with MIC of 25, 100, and 150 mg/mL could inhibit the growth of S. aureus, P. aeruginosa, and MRSA, respectively. Bacopa monnieri with MIC of 50 mg/mL and 100 mg/mL inhibited the growth of S. aureus and P. aeruginosa, respectively. Centella asiatica did not affect the studied strains. The fractional inhibitory concentration (FIC) results showed partial synergistic activity between S. limbata with ceftazidime and neomycin against P. aeruginosa and MRSA. The MIC of ceftazidime and neomycin in combination with S. limbata was reduced fourfold for each antibiotic. Conclusion: Salvia limbata is a potentially rich source of bioactive compounds with antimicrobial properties that can be used with ceftazidime and neomycin to provide a synergistic effect.


Main Subjects

  • Blair JMA, Webber MA, Baylay AJ, Ogbolu DO, Piddock LJV. Molecular mechanisms of antibiotic resistance. Nat Rev Microbiol. 2015; 13(1): 42–51.
  • Giedraitiene A, Vitkauskiene A, Naginiene R, Pavilonis A. Antibiotic resistance mechanisms of clinically important bacteria. Medicina (Kaunas). 2011; 47(3): 137–146.
  • World Health Organization. WHO methods and data sources for global burden of disease estimates 2000-2011. [Accessed 2022]. Available from:
  • World Health Organization. Antimicrobial resistance: global report on surveillance; 2014. [Accessed 2022]. Available from:
  • Carr C, Smith A, Marturano M, Hakki L, Friedman J, Guidry C,  McGrew P,  McGinness C, Juan Duchesne J,  Schroll R . Ventilator associated pneumonia: how do the different criteria for diagnosis match up? Am Surg. 2019; 85(9): 992–997.
  • Pelfrene E, Botgros R, Cavaleri M. Antimicrobial multidrug resistance in the era of COVID-19: a forgotten plight? Antimicrob Resist Infect Control. 2021; 10(1): 1–6.
  • Strathdee SA, Davies SC, Marcelin JR. Confronting antimicrobial resistance beyond the COVID-19 pandemic and the 2020 US election. Lancet. 2020; 396(10257): 1050–1053.
  • Malmir S, Bahreinian M, Zahiri Yeganeh S, Mirnejad R, Moosazadeh Moghaddam M, Saberi F. Molecular mechanisms of resistance to conventional antibiotics in bacteria. Int J Med Rev. 2018; 5(3): 118–129.
  • Khameneh B, Iranshahy M, Soheili V, Bazzaz BSF. Review on plant antimicrobials: a mechanistic viewpoint. Antimicrob Resist Infect Control.  2019; 8(1): 118–145.
  • Keyes K, Lee MD, Maurer JJ. Antibiotics: mode of action, mechanisms of resistance, and transfer. In: Torrence ME, Isaacson RE, Eds. Microbial food safety in animal agriculture: current topics. Iowa: Iowa State Press, 2003.
  • Alekshun MN, Levy SB. Molecular mechanism of antibacterial maltidrug resistance. 2007; 128(6): 1037–1050.
  • Hosseini SMJ, Saberi M, Hosseini Doust SR, Yaribeigi H. Evaluation of antibiotic resistance in bacteria isolated from patients hospitalized in Imam Khomeini and burn hospitals in Ahvaz City, Iran. Qom Univ Med Sci J. 2013; 7(6): 21–26.
  • Carroll KC, Hobden JA, Miller S, Morse SA, Mietzner TA, Detrick B, Mitchell TG, Mc Kerrow JH, Sakanari JA, Eds. Jawetz, Melnick & Adelberg’s medical microbiology. New York: McGraw Hill, 2019.
  • Llamazares C, Del Olmo NS, Soliveri J, Javier de la Mata F, Copa-Patiño JL, García-Gallego S. Insight on the structure-to-activity of carbosilane metallodendrimers in the fight against Staphylococcus aureus Antibiotics. 2021; 10(5): 2–12.
  • Chew YL, Mahadi AM, Wong KM, Kheng Goh J. Anti-methicillin-resistance Staphylococcus aureus (MRSA) compounds from Bauhinia kockiana Korth and their mechanism of antibacterial activity. BMC Complement Altern Med. 2018; 18(1): 70–78.
  • Hawkey PM, Warren RE, Livermore DM, McNulty CAM, Enoch DA, Otter JA, Wilson APR. Treatment of infections caused by multidrug-resistant Gram-negative bacteria: report of the British society for antimicrobial chemotherapy/healthcare infection society/British infection association joint working party. J Antimicrob Chemother. 2018; 73(3): 2–78.
  • Wanger VE, Iglewski BH. aeruginosa biofilms in CF infection. Clin Rev Allergy Immunol. 2008; 35(3): 124–134.
  • Sun D, Crowell SA, Harding CM, Silva PMD, Harrison A, Fernando DM, Mason KM, Santana E, Loewen PC, Kumar A, Liu Y. KatG and KatE Confer Acinetobacter resistance to hydrogen peroxide but sensitize bacteria to killing by phagocytic respiratory burst. Life Sci. 2016; 148: 31–40.
  • Protic D, Pejovic A, Andjelkovic D, Djukanovic N, Savic D, Piperac P, Markovic Denic L, Zdravkovic M, Todorovic Z. Nosocomial infections caused by Acinetobacter baumannii: are we losing the battle? Surg Infect. 2016; 17(2): 236–242.
  • Rajabi Z, Ebrahimi M, Farajpour M, Mirza M, Ramshini H. Compositions and yield variation of essential oils among and within nine Salvia species from various areas of Iran. Ind Crop Prod. 2014; 61: 233–239.
  • Iravani M, Mahinpour R, Zahraei Z, Toluei Z. In vitro evaluation of the antimicrobial properties of essential oils and methanolic extracts of four species of Salvia Res Med. 2019; 43(3): 157–163.
  • Vijay R, Shukla J, Saxena R. Propagation of Bacopa monnieri (BRAHMI): important medicinal plant. CIBTech J Biotechnol. 2016; 5(3): 17–23.
  • Wong JX, Ramli S. Antimicrobial activity of different types of Centella asiatica extracts against foodborne pathogens and food spoilage microorganisms. LWT. 2021; 142: 1–6.
  • Shafizadeh gerdkohi H, Ramezani V, Eslahi E, Emami A, Ranjbar AM, Tavakoli F. Effect of hydroalcoholic extract of Oliveria decumbens Vent on diarrhea and symptoms of morphine withdrawal syndrome in mice. Sci J Kurdistan Uni Med Sci. 2021; 26(3): 1–12.
  • Slinkard K, Singleton VL. Total phenol analysis: automation and comparison with manual methods. Am J Enol Vitic. 1977; 28(1): 49–55.
  • Balouiri M, Sadiki M, Ibnsouda SK. Methods for in vitro evaluating antimicrobial activity: a review. J Pharm Anal. 2016; 6(2): 71–79.
  • Moussa SH, Tayel AA, Al-Hassan AA, Farouk A. Tetrazolium/formazan test as an efficient method to determine fungal chitosan antimicrobial activity. J Mycology. 2013; Article ID 753692.
  • Vazirian M, Hamidian KH, Noorollah M, Manayi A, Samadi N. Enhancement of antibiotic activity and reversal of resistance in clinically isolated methicillin-resistant Staphylococcus aureus by Trachyspermum ammi essential oil. Res J Pharmacogn. 2019; 6(1): 1–10.
  • Bhatia P, Sharma A, George AJ, Anvitha D, Kumar P, Dwivedi VP, Chandra Antibacterial activity of medicinal plants against ESKAPE: an update. Heliyon. 2021; 7(2): 1–12.
  • Alam MZ, Ahmad Khan Phytomedicine from Middle Eastern countries: an alternative remedy to modern medicine against Candida spp. infection. Evid Based Complement Altern Med. 2021; Article ID 6694876.
  • Jafari B, Jafari Sales A, Khaneshpour H, Fatemi S, Pashazadeh M, Al-Snafi AE, Shariat A. Ntibacterial effects of Thymus vulgaris, Mentha pulegium, Crocus sativus and Salvia officinalis on pathogenic bacteria: a brief review study based on Gram- positive and Gram-negative bacteria. Jorjani Biomed J. 2020; 8(3): 58–74.
  • Stefanović OD,  Stanojević DD,  Comić Synergistic antibacterial activity of Salvia officinalis and Cichorium intybus extracts and antibiotics. Acta Pol Pharm. 2012; 69(3): 457–463.
  • Amirian F, Kazemi Pour N, Khoshroo SMR, Sayadi A, Karmostaji A, Mousavi SM. Synergistic effect and antibacterial activities of extracts of Salvia and Rosemary officinalis against Esherichia coli isolated from clinical urinary tract infection. Ann Mil Health Sci Res. 2017; 15(4): 1–7.
  • Bandian L, Moghaddam M, Bahraini M. Investigate the antimicrobial activity and synergistic effects of Zataria multiflora, Salvia verticillata and Froriepia subpinnata ethanolic extracts on bacterial vegetables decay. J Food Microbiol. 2021; 8(1): 45–57.
  • Fazlul MKK, Deepthi SP, Mohammed I, Farzana Y, Munira B, Nazmulmhm Antibacterial and antifungal activity of various extract Bacopa monnieri. Int J Pharm Res. 2019; 11(1): 2–25.