Efflux Pump Inhibitors Derived From Natural Sources as Novel Antibacterial Agents Against Pseudomonas aeruginosa: A Review

Document Type : Narrative Review

Authors

1 Department of Microbiology and Applied Microbiology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran

2 Department of Microbiology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran

3 Department of Microbiology, Faculty of Medicine, Birjand University of Medical Sciences, Birjand, Iran

Abstract

Infections resulting from Pseudomonas aeruginosa are important due to their highest resistance against all clinically used antibiotics. To date, 11 different efflux pumps of the RND family in P. aeruginosa that enable the efflux of antibiotics/anti-microbial production have been detected. Carvacrol of Satureja khuzestanica is one of the most effective compounds with the ability to affect bacteria. This study aimed to evaluate herbal compounds with inhibitory activities. These pumps include MexAB-OprM, MexCD-OprJ, MexEF-OprN, MexGHI-OpmD, MexJK-OprM/OpmH, MexMN, MexPQ-OpmE, MexVW-OprM, MexXY-OprM, TriABC-OpmH, and MuxABC-OpmB (1). Unfortunately, among bacteria, P. aeruginosa are highly resistant to drug compounds (3). Because of this high resistance, its importance in nosocomial infections and burns, and that it often causes diseases in immunocompromised patients, finding a therapeutic supplement is essential. In this study, drug compounds against efflux pump genes were sought.

Keywords


  1. Hirakata Y, Kondo A, Hoshino K, et al. Efflux pump inhibitors reduce the invasiveness of Pseudomonas aeruginosa. Int J Antimicrob Agents. 2009;34(4):343-346. doi:10.1016/j.ijantimicag.2009.06.007.
  2. Alp E, Guven M, Yildiz O, Aygen B, Voss A, Doganay M. Incidence, risk factors and mortality of nosocomial pneumonia in intensive care units: a prospective study. Ann Clin Microbiol Antimicrob. 2004;3:17. doi:10.1186/1476-0711-3-17.
  3. Leid JG, Kerr M, Selgado C, et al. Flagellum-mediated biofilm defense mechanisms of Pseudomonas aeruginosa against host-derived lactoferrin. Infect Immun. 2009;77(10):4559-4566. doi:10.1128/IAI.00075-09.
  4. Nikaido H. Prevention of drug access to bacterial targets: permeability barriers and active efflux. Science. 1994;264(5157) :382-388. doi:10.1126/science.8153625.
  5. Li XZ, Nikaido H. Efflux-mediated drug resistance in bacteria: an update. Drugs. 2009;69(12):1555-1623. doi:10.2165/11317030-000000000-00000.
  6. Poole K. Efflux-mediated multiresistance in Gram-negative bacteria. Clin Microbiol Infect. 2004;10(1):12-26. doi:10.1111/j.1469-0691.2004.00763.x.
  7. Poole K, Krebes K, McNally C, Neshat S. Multiple antibiotic resistance in Pseudomonas aeruginosa: evidence for involvement of an efflux operon. J Bacteriol. 1993;175(22):7363-7372. doi:10.1128/jb.175.22.7363-7372.1993.
  8. Breidenstein EB, de la Fuente-Nunez C, Hancock RE. Pseudomonas aeruginosa: all roads lead to resistance. Trends Microbiol. 2011;19(8):419-426. doi:10.1016/j.tim.2011.04.005.
  9. Stavri M, Piddock LJ, Gibbons S. Bacterial efflux pump inhibitors from natural sources. J Antimicrob Chemother. 2007;59(6):1247- 1260. doi:10.1093/jac/dkl460.
  10. Van Bambeke F, Michot JM, Tulkens PM. Antibiotic efflux pumps in eukaryotic cells: occurrence and impact on antibiotic cellular pharmacokinetics, pharmacodynamics and toxicodynamics. J Antimicrob Chemother. 2003;51(5):1067-1077. doi:10.1093/jac/dkg225.
  11. Zechini B, Versace I. Inhibitors of multidrug resistant efflux systems in bacteria. Recent Pat Antiinfect Drug Discov. 2009;4(1):37-50. doi:10.2174/157489109787236256.
  12. Chopra I. New developments in tetracycline antibiotics: glycylcyclines and tetracycline efflux pump inhibitors. Drug Resist Updat. 2002;5(3-4):119-125. doi:10.1016/S1368-7646(02)00051-1.
  13. Kumar A, Schweizer HP. Bacterial resistance to antibiotics: active efflux and reduced uptake. Adv Drug Deliv Rev. 2005;57(10):1486- 1513. doi:10.1016/j.addr.2005.04.004.
  14. Fernando DM, Kumar A. Resistance-nodulation-division multidrug efflux pumps in gram-negative bacteria: role in virulence. Antibiotics (Basel). 2013;2(1):163-181. doi:10.3390/antibiotics2010163.
  15. Vidal-Aroca F, Meng A, Minz T, Page MG, Dreier J. Use of resazurin to detect mefloquine as an efflux-pump inhibitor in Pseudomonas aeruginosa and Escherichia coli. J Microbiol Methods. 2009;79(2):232-237. doi:10.1016/j.mimet.2009.09.021.
  16. Piddock LJ. Clinically relevant chromosomally encoded multidrug resistance efflux pumps in bacteria. Clin Microbiol Rev. 2006;19(2):382-402. doi:10.1128/CMR.19.2.382-402.2006.
  17. Van Bambeke F, Balzi E, Tulkens PM. Antibiotic efflux pumps. Biochem Pharmacol. 2000;60(4):457-470. doi:10.1016/S0006-2952(00)00291-4.
  18. Zgurskaya HI, Nikaido H. AcrA is a highly asymmetric protein capable of spanning the periplasm. J Mol Biol. 1999;285(1):409- 420. doi:10.1006/jmbi.1998.2313.
  19. Tegos GP, Haynes M, Strouse JJ, et al. Microbial efflux pump inhibition: tactics and strategies. Curr Pharm Des. 2011;17(13):1291-1302. doi:10.2174/138161211795703726.
  20. Misra R, Bavro VN. Assembly and transport mechanism of tripartite drug efflux systems. Biochim Biophys Acta. 2009;1794(5):817- 825. doi:10.1016/j.bbapap.2009.02.017.
  21. Han XY, De I, Jacobson KL. Rapidly growing mycobacteria: clinical and microbiologic studies of 115 cases. Am J Clin Pathol. 2007;128(4):612-621. doi:10.1309/1KB2GKYT1BUEYLB5.
  22. Masuda N, Sakagawa E, Ohya S, Gotoh N, Tsujimoto H, Nishino T. Substrate specificities of MexAB-OprM, MexCD-OprJ, and MexXY-oprM efflux pumps in Pseudomonas aeruginosa. Antimicrob Agents Chemother. 2000;44(12):3322-3327. doi:10.1128/AAC.44.12.3322-3327.2000.
  23. Van Bambeke F, Pages JM, Lee VJ. Inhibitors of bacterial efflux pumps as adjuvants in antibiotic treatments and diagnostic tools for detection of resistance by efflux. Recent Pat Antiinfect Drug Discov. 2006;1(2):157-175. doi:10.2174/157489106777452692.
  24. Strateva T, Yordanov D. Pseudomonas aeruginosa - a phenomenon of bacterial resistance. J Med Microbiol. 2009;58(Pt 9):1133- 1148. doi:10.1099/jmm.0.009142-0.
  25. Li XZ, Plesiat P, Nikaido H. The challenge of efflux-mediated antibiotic resistance in gram-negative bacteria. Clin Microbiol Rev. 2015;28(2):337-418. doi:10.1128/CMR.00117-14.
  26. Zhanel GG, Hoban DJ, Schurek K, Karlowsky JA. Role of efflux mechanisms on fluoroquinolone resistance in Streptococcus pneumoniae and Pseudomonas aeruginosa. Int J Antimicrob Agents. 2004;24(6):529-535. doi:10.1016/j.ijantimicag.2004.08.003.
  27. Avrain L, Mertens P, Van Bambeke F. RND efflux pumps in P. aeruginosa: an underestimated resistance mechanism. 2013; 26- 28.
  28. Lister PD, Wolter DJ, Hanson ND. Antibacterial-resistant Pseudomonas aeruginosa: clinical impact and complex regulation of chromosomally encoded resistance mechanisms. Clin Microbiol Rev. 2009;22(4):582-610. doi:10.1128/CMR.00040-09.
  29. Venter H, Mowla R, Ohene-Agyei T, Ma S. RND-type drug e ffl ux pumps from Gram-negative bacteria: molecular mechanism and inhibition. Front Microbiol. 2015;6:377. doi:10.3389/fmicb.2015.00377.
  30. Welch A, Awah CU, Jing S, van Veen HW, Venter H. Promiscuous partnering and independent activity of MexB, the multidrug transporter protein from Pseudomonas aeruginosa. Biochem J. 2010;430(2):355-364. doi:10.1042/BJ20091860.
  31. Poole K, Srikumar R. Multidrug efflux in Pseudomonas aeruginosa: components, mechanisms and clinical significance. Curr Top Med Chem. 2001;1(1):59-71. doi:10.2174/1568026013395605.
  32. Poole K. Efflux-mediated antimicrobial resistance. J Antimicrob Chemother. 2005;56(1):20-51. doi:10.1093/jac/dki171.
  33. Jeannot K, Elsen S, Kohler T, Attree I, van Delden C, Plesiat P. Resistance and virulence of Pseudomonas aeruginosa clinical strains overproducing the MexCD-OprJ efflux pump. Antimicrob Agents Chemother. 2008;52(7):2455-2462. doi:10.1128/AAC.01107-07.
  34. Dean CR, Visalli MA, Projan SJ, Sum PE, Bradford PA. Efflux-mediated resistance to tigecycline (GAR-936) in Pseudomonas aeruginosa PAO1. Antimicrob Agents Chemother. 2003;47(3):972- 978. doi:10.1128/AAC.47.3.972-978.2003.
  35. He GX, Kuroda T, Mima T, Morita Y, Mizushima T, Tsuchiya T. An H(+)-coupled multidrug efflux pump, PmpM, a member of the MATE family of transporters, from Pseudomonas aeruginosa. J Bacteriol. 2004;186(1):262-265. doi:10.1128/JB.186.1.262-265.2004.
  36. Gales AC, Jones RN, Sader HS. Global assessment of the antimicrobial activity of polymyxin B against 54 731 clinical isolates of gram-negative bacilli: report from the SENTRY antimicrobial surveillance programme (2001-2004). Clin Microbiol Infect. 2006;12(4):315-321. doi:10.1111/j.1469-0691.2005.01351.x.
  37. Garvey MI, Rahman MM, Gibbons S, Piddock LJ. Medicinal plant extracts with efflux inhibitory activity against gram-negative bacteria. Int J Antimicrob Agents. 2011;37(2):145-151. doi:10.1016/j.ijantimicag.2010.10.027.
  38. Pages JM, Amaral L. Mechanisms of drug efflux and strategies to combat them: challenging the efflux pump of Gram-negative bacteria. Biochim Biophys Acta. 2009;1794(5):826-833. doi:10.1016/j.bbapap.2008.12.011.
  39. Chitemerere TA, Mukanganyama S. In vitro antibacterial activity of selected medicinal plants from Zimbabwe. Afr J Plant Sci Biotechnol. 2011;5(1):1-7.
  40. Mahamoud A, Chevalier J, Alibert-Franco S, Kern WV, Pages JM. Antibiotic efflux pumps in gram-negative bacteria: the inhibitor response strategy. J Antimicrob Chemother. 2007;59(6):1223- 1229. doi:10.1093/jac/dkl493.
  41. Ambudkar SV, Dey S, Hrycyna CA, Ramachandra M, Pastan I, Gottesman MM. Biochemical, cellular, and pharmacological aspects of the multidrug transporter. Annu Rev Pharmacol Toxicol. 1999;39:361-398. doi:10.1146/annurev.pharmtox.39.1.361.
  42. Eid SY, El-Readi MZ, Fatani SH, Eldin EE, Wink M. Natural products modulate the multifactorial multidrug resistance of cancer. Pharmacol Pharm. 2015;6(3):146-176. doi:10.4236/ pp.2015.63017.
  43. Hohl AF, Frei R, Punter V, et al. International multicenter investigation of LB20304, a new fluoronaphthyridone. Clin Microbiol Infect. 1998;4(5):280-284. doi:10.1111/j.1469-0691.1998.tb00057.x.
  44. Vadlapatla RK, Vadlapudi AD, Kwatra D, Pal D, Mitra AK. Differential effect of P-gp and MRP2 on cellular translocation of gemifloxacin. Int J Pharm. 2011;420(1):26-33. doi:10.1016/j.ijpharm.2011.08.009.
  45. Kullak-Ublick GA, Becker MB. Regulation of drug and bile salt transporters in liver and intestine. Drug Metab Rev. 2003;35(4):305- 317. doi:10.1081/DMR-120026398.
  46. Rice A, Liu Y, Michaelis ML, Himes RH, Georg GI, Audus KL. Chemical modification of paclitaxel (Taxol) reduces P-glycoprotein interactions and increases permeation across the blood-brain barrier in vitro and in situ. J Med Chem. 2005;48(3):832-838. doi:10.1021/jm040114b.
  47. Colegate SM, Molyneux RJ, editors. Bioactive natural products: detection, isolation, and structural determination. 2nd ed. Boca Raton: CRC Press; 2008.
  48. Conseil G, Baubichon-Cortay H, Dayan G, Jault JM, Barron D, Di Pietro A. Flavonoids: a class of modulators with bifunctional interactions at vicinal ATP- and steroid-binding sites on mouse P-glycoprotein. Proc Natl Acad Sci U S A. 1998;95(17):9831-9836. doi:10.1073/pnas.95.17.9831.
  49. Bohnert JA, Szymaniak-Vits M, Schuster S, Kern WV. Efflux inhibition by selective serotonin reuptake inhibitors in Escherichia coli. J Antimicrob Chemother. 2011;66(9):2057-2060. doi:10.1093/jac/dkr258.
  50. Ricci V, Busby SJ, Piddock LJ. Regulation of RamA by RamR in Salmonella enterica serovar Typhimurium: isolation of a RamR superrepressor. Antimicrob Agents Chemother. 2012;56(11):6037- 6040. doi:10.1128/AAC.01320-12.
  51. Jalalvandi N, Bahador A, Zahedi B, Saghi H, Esmaeili D. The study of inhibitory effects of Satureja khuzestanica essence against mexa and mexr efflux genes of Pseudomonas aeruginosa by Rt-Pcr. Int J Biotechnol. 2015;4(1):1-8. doi:10.18488/ journal.57/2015.4.1/57.1.1.8.
  52. Tikhonova EB, Yamada Y, Zgurskaya HI. Sequential mechanism of assembly of multidrug efflux pump AcrAB-TolC. Chem Biol. 2011;18(4):454-463. doi:10.1016/j.chembiol.2011.02.011.
  53. Venter H, Shilling RA, Velamakanni S, Balakrishnan L, Van Veen HW. An ABC transporter with a secondary-active multidrug translocator domain. Nature. 2003;426(6968):866-870. doi:10.1038/nature02173.
  54. Askoura M, Mottawea W, Abujamel T, Taher I. Efflux pump inhibitors (EPIs) as new antimicrobial agents against Pseudomonas aeruginosa. Libyan J Med. 2011;6. doi:10.3402/ljm.v6i0.5870.
  55. Tegos G, Stermitz FR, Lomovskaya O, Lewis K. Multidrug pump inhibitors uncover remarkable activity of plant antimicrobials. Antimicrob Agents Chemother. 2002;46(10):3133-3141. doi:10.1128/AAC.46.10.3133-3141.2002.
  56. Lomovskaya O, Warren MS, Lee A, et al. Identification and characterization of inhibitors of multidrug resistance efflux pumps in Pseudomonas aeruginosa: novel agents for combination therapy. Antimicrob Agents Chemother. 2001;45(1):105-116. doi:10.1128/AAC.45.1.105-116.2001.
  57. Opperman TJ, Nguyen ST. Recent advances toward a molecular mechanism of efflux pump inhibition. Front Microbiol. 2015;6:421. doi:10.3389/fmicb.2015.00421.
  58. Okandeji BO, Greenwald DM, Wroten J, Sello JK. Synthesis and evaluation of inhibitors of bacterial drug efflux pumps of the major facilitator superfamily. Bioorg Med Chem. 2011;19(24):7679- 7689. doi:10.1016/j.bmc.2011.10.011.
  59. Lomovskaya O, Bostian KA. Practical applications and feasibility of efflux pump inhibitors in the clinic--a vision for applied use. Biochem Pharmacol. 2006;71(7):910-918. doi:10.1016/j.bcp.2005.12.008.
  60. Aparna V, Dineshkumar K, Mohanalakshmi N, Velmurugan D, Hopper W. Identification of natural compound inhibitors for multidrug efflux pumps of Escherichia coli and Pseudomonas aeruginosa using in silico high-throughput virtual screening and in vitro validation. PLoS One. 2014;9(7):e101840. doi:10.1371/journal.pone.0101840.
  61. Bhardwaj AK, Mohanty P. Bacterial efflux pumps involved in multidrug resistance and their inhibitors: rejuvinating the antimicrobial chemotherapy. Recent Pat Antiinfect Drug Discov. 2012;7(1):73-89. doi:10.2174/157489112799829710.
  62. Mahamoud A, Chevalier J, Davin-Regli A, Barbe J, Pages JM. Quinoline derivatives as promising inhibitors of antibiotic efflux pump in multidrug resistant Enterobacter aerogenes isolates. Curr Drug Targets. 2006;7(7):843-847. doi:10.2174/138945006777709557.
  63. Wang D, Gao F. Quinazoline derivatives: synthesis and bioactivities. Chem Cent J. 2013;7(1):95. doi:10.1186/1752-153X-7-95.
  64. Mahamoud A, Chevalier J, Baitiche M, Adam E, Pages JM. An alkylaminoquinazoline restores antibiotic activity in gram-negative resistant isolates. Microbiology. 2011;157(Pt 2):566-571. doi:10.1099/mic.0.045716-0.
  65. Lee MD, Galazzo JL, Staley AL, et al. Microbial fermentation-derived inhibitors of efflux-pump-mediated drug resistance. Farmaco. 2001;56(1-2):81-85. doi:10.1016/S0014-827X(01)01002-3.
  66. Lorenzi V, Muselli A, Bernardini AF, et al. Geraniol restores antibiotic activities against multidrug-resistant isolates from gram-negative species. Antimicrob Agents Chemother. 2009;53(5):2209- 2211. doi:10.1128/AAC.00919-08.
  67. Negi N, Prakash P, Gupta ML, Mohapatra TM. Possible role of curcumin as an efflux pump inhibitor in multi drug resistant clinical isolates of Pseudomonas aeruginosa. J Clin Diagn Res. 2014;8(10):Dc04-07. doi:10.7860/JCDR/2014/8329.4965.
  68. Rana T, Singh S, Kaur K, Pathania K, Farooq U. A review on efflux pump inhibitors of medically important bacteria from plant sources. Int J Pharm Sci Rev Res. 2014;26(2):101-111.
  69. Piddock LJ, Garvey MI, Rahman MM, Gibbons S. Natural and synthetic compounds such as trimethoprim behave as inhibitors of efflux in gram-negative bacteria. J Antimicrob Chemother. 2010;65(6):1215-1223. doi:10.1093/jac/dkq079.
  70. Kristiansen JE, Thomsen VF, Martins A, Viveiros M, Amaral L. Non-antibiotics reverse resistance of bacteria to antibiotics. In Vivo. 2010;24(5):751-754.
  71. Amusan OOG, Sukati NA, Dlamini PS, Sibandze FG. Some Swazi phytomedicines and their constituents. Afr J Biotechnol. 2007;6(3):267-272.
  72. Ruegg T, Calderon AI, Queiroz EF, et al. 3-Farnesyl-2- hydroxybenzoic acid is a new anti-Helicobacter pylori compound from Piper multiplinervium. J Ethnopharmacol. 2006;103(3):461- 467. doi:10.1016/j.jep.2005.09.014.
  73. Cherigo L, Pereda-Miranda R, Fragoso-Serrano M, Jacobo-Herrera N, Kaatz GW, Gibbons S. Inhibitors of bacterial multidrug efflux pumps from the resin glycosides of Ipomoea murucoides. J Nat Prod. 2008;71(6):1037-1045. doi:10.1021/np800148w.
  74. Kumar A, Khan IA, Koul S, et al. Novel structural analogues of piperine as inhibitors of the NorA efflux pump of Staphylococcus aureus. J Antimicrob Chemother. 2008;61(6):1270-1276. doi:10.1093/jac/dkn088.
  75. Fadli M, Chevalier J, Saad A, Mezrioui NE, Hassani L, Pages JM. Essential oils from Moroccan plants as potential chemosensitisers restoring antibiotic activity in resistant gram-negative bacteria. Int J Antimicrob Agents. 2011;38(4):325-330. doi:10.1016/j.ijantimicag.2011.05.005.
  76. Kamatou GPP, van Zyl RL, van Vuuren SF, et al. Chemical composition, leaf trichome types and biological activities of the essential oils of four related Salvia species indigenous to southern Africa. J Essent Oil Res. 2006;18:72-79.
  77. Andrews JM. Determination of minimum inhibitory concentrations. J Antimicrob Chemother. 2001;48 Suppl 1:5-16. doi:10.1093/jac/48.suppl_1.5.
  78. Nakashima R, Sakurai K, Yamasaki S, Nishino K, Yamaguchi A. Structures of the multidrug exporter AcrB reveal a proximal multisite drug-binding pocket. Nature. 2011;480(7378):565-569. doi:10.1038/nature10641.
  79. Ohene-Agyei T, Mowla R, Rahman T, Venter H. Phytochemicals increase the antibacterial activity of antibiotics by acting on a drug efflux pump. Microbiologyopen. 2014;3(6):885-896. doi:10.1002/mbo3.212.
  80. Odds FC. Synergy, antagonism, and what the chequerboard puts between them. J Antimicrob Chemother. 2003;52(1):1. doi:10.1093/jac/dkg301.
  81. Seasotiya L, Dalal S. Screening of Indian medicinal plants as efflux pump inhibitors of fluoroquinolones. J Pharmacogn Phytochem. 2014;3(1):235-241.
  82. Neyfakh AA, Bidnenko VE, Chen LB. Efflux-mediated multidrug resistance in Bacillus subtilis: similarities and dissimilarities with the mammalian system. Proc Natl Acad Sci U S A. 1991;88(11):4781-4785. doi:10.1073/pnas.88.11.4781.
  83. Khan IA, Mirza ZM, Kumar A, Verma V, Qazi GN. Piperine, a phytochemical potentiator of ciprofloxacin against Staphylococcus aureus. Antimicrob Agents Chemother. 2006;50(2):810-812. doi:10.1128/AAC.50.2.810-812.2006.
  84. Zhanel GG, Hoban DJ, Schurek K, Karlowsky JA. Role of efflux mechanisms on fluoroquinolone resistance in Streptococcus pneumoniae and Pseudomonas aeruginosa. Int J Antimicrob Agents. 2004;24(6):529-535. doi:10.1016/j.ijantimicag.2004.08.003.
  85. Touani FK, Seukep AJ, Djeussi DE, Fankam AG, Noumedem JA, Kuete V. Antibiotic-potentiation activities of four Cameroonian dietary plants against multidrug-resistant gram-negative bacteria expressing efflux pumps. BMC Complement Altern Med. 2014;14:258. doi:10.1186/1472-6882-14-258.
  86. Melero C, Medarde M, San Feliciano A. A short review on cardiotonic steroids and their aminoguanidine analogues. Molecules. 2000;5(1):51-81. doi:10.3390/50100051.
  87. Ghisalberti D, Mahamoud A, Chevalier J, et al. Chloroquinolines block antibiotic efflux pumps in antibiotic-resistant Enterobacter aerogenes isolates. Int J Antimicrob Agents. 2006;27(6):565-569. doi:10.1016/j.ijantimicag.2006.03.010.
  88. Seeger MA, von Ballmoos C, Eicher T, et al. Engineered disulfide bonds support the functional rotation mechanism of multidrug efflux pump AcrB. Nat Struct Mol Biol. 2008;15(2):199-205. doi:10.1038/nsmb.1379.
  89. Cha HJ, Muller RT, Pos KM. Switch-loop flexibility affects transport of large drugs by the promiscuous AcrB multidrug efflux transporter. Antimicrob Agents Chemother. 2014;58(8):4767- 4772. doi:10.1128/AAC.02733-13.
  90. Musumeci R, Speciale A, Costanzo R, et al. Berberis aetnensis C. Presl. extracts: antimicrobial properties and interaction with ciprofloxacin. Int J Antimicrob Agents. 2003;22(1):48-53. doi:10.1016/S0924-8579(03)00085-2.
  91. Bohnert JA, Karamian B, Nikaido H. Optimized Nile Red efflux assay of AcrAB-TolC multidrug efflux system shows competition between substrates. Antimicrob Agents Chemother. 2010;54(9):3770-3775. doi:10.1128/AAC.00620-10.
  92. Poonsuk K, Chuanchuen R. Contribution of the MexXY multidrug efflux pump and other chromosomal mechanisms on aminoglycoside resistance in Pseudomonas aeruginosa isolates from canine and feline infections. J Vet Med Sci. 2012;74(12):1575- 1582. doi:10.1292/jvms.12-0239.
  93. Avrain L, Hocquet D, Laurent T, Leclipteux T, Mertens P. Pre-Real- Time PCR steps standardization for appropriate interpretation of mexA and mexX gene expression by mex Q-Test in P. aeruginosa. ECCMID; 2010:590.
  94. Boucher HW, Talbot GH, Bradley JS, et al. Bad bugs, no drugs: no ESKAPE! An update from the Infectious Diseases Society of America. Clin Infect Dis. 2009;48(1):1-12. doi:10.1086/595011.
  95. Raja A, Gajalakshmi P, Mohamed Mahroop Raja M. Drugs from the natural bio sources for human disease. Int J Pharmacol. 2010;6(4):360-363. doi:10.3923/ijp.2010.360.363.
  96. Stermitz FR, Lorenz P, Tawara JN, Zenewicz LA, Lewis K. Synergy in a medicinal plant: antimicrobial action of berberine potentiated by 5’-methoxyhydnocarpin, a multidrug pump inhibitor. Proc Natl Acad Sci U S A. 2000;97(4):1433-1437. doi:10.1073/pnas.030540597.
  97. Page MG, Heim J. Prospects for the next anti-Pseudomonas drug. Curr Opin Pharmacol. 2009;9(5):558-565. doi:10.1016/j.coph.2009.08.006.