Mechanistic Insights into Antibiofilm Activity Against Meropenem-Resistant Acinetobacter baumannii Mechanistic Evaluation of Antibiofilm Activity Against Meropenem-Resista
Article Sidebar
Main Article Content
Abstract
Acinetobacter baumannii is considered the third most common cause of catheter-associated urinary tract infections (UTIs). Its ability to form biofilms and produce urease contributes to catheter blockage, enhancing its virulence and reducing the effectiveness of antibiotics. UTIs caused by A. baumannii are increasingly concerning, and meropenem remains a last-resort treatment for infections caused by this pathogen. However, the emergence of meropenem-resistant (MER-R) A. baumannii has severely compromised its clinical effectiveness. This study aimed to investigate the antibiofilm activity and underlying mechanisms associated with MER-R A. baumannii. Urine samples were collected from 102 patients referred to Baghdad Medical City and immediately placed in sterile tubes before initial culture on MacConkey agar. Identification and confirmation of bacterial isolates were performed using the Vitek® 2 Compact system with a Gram-negative (GN) identification card, which includes 48 biochemical tests. Antibiotic susceptibility testing and biofilm activity assays of A. baumannii were also conducted. The results confirmed the isolation of A. baumannii. Antibiotic susceptibility testing revealed that a sub-minimum inhibitory concentration (sub-MIC) of 62 µg/mL meropenem exhibited a significant biofilm-inhibitory effect against multidrug-resistant wild-type A. baumannii strains. Strong biofilm-producing isolates were incubated with 1 mL of sub-MIC colistin for 24 and 48 hours at 37 °C. Meropenem was further evaluated for its ability to inhibit biofilm formation by A. baumannii. Conclusion: This study highlighted the mechanisms underlying antibiofilm activity against meropenem-resistant A. baumannii. Targeting biofilm formation and associated virulence factors can significantly reduce bacterial colonization and catheter obstruction, offering a promising strategy to enhance treatment efficacy and improve patient outcomes. These findings provide valuable insights for developing alternative therapeutic approaches against multidrug-resistant A. baumannii infections.
Article Details
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
The Journal of Medical and Oral Biosciences uses a Creative Commons Attribution (CC Attribution-ShareAlike 4.0) and its license of (CC BY-SA 4.0). This license allows the authors to hold ownership of the copyright of their articles.
Attribution-Share Alike 4.0 International License (CC BY-SA 4.0). 
Under the CC BY-SA 4.0 the authors are free to:
Share — copy and redistribute the material in any medium or format for any purpose, even commercially.
Adapt — remix, transform, and build upon the material for any purpose, even commercially.
The licensor cannot revoke these freedoms as long as you follow the license terms.
Under the following terms:
Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
ShareAlike — If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original.
No additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.
No use, distribution or reproduction is permitted which does not comply with these terms.
https://creativecommons.org/licenses/by-sa/4.0/
References
1. Abbo A, Carmeli Y, Navon-Venezia S, Siegman-Igra Y, Schwaber MJ. Impact of multidrug-resistant Acinetobacter baumannii on clinical outcomes. Eur J Clin Microbiol Infect Dis. 2007;26(11):793–800. doi:10.1007/s10096-007-0371-8
2. Peleg AY, Seifert H, Paterson DL. Acinetobacter baumannii: emergence of a successful pathogen. Clin Microbiol Rev. 2008;21(3):538–582. doi:10.1128/CMR.00058-07
3. Whiteway C, Breine A, Philippe C, Van der Henst C. Acinetobacter baumannii. Trends Microbiol. 2022;30(2):199–200. doi:10.1016/j.tim.2021.11.008
4. The migration of carbapenem-resistant Acinetobacter baumannii from the battlefields of Iraq and Afghanistan to the healthcare facilities of the Veterans Health Administration" (2021). Capstone Experience: Master of Public Health. 145.
https://digitalcommons.unmc.edu/coph_slce/145
5. Gaynes R, Edwards JR. Overview of nosocomial infections caused by Gram-negative bacilli. Clin Infect Dis. 2005;41(6):848–854. doi:10.1086/432803
6. Jung SY, Lee SH, Lee SY, et al. Antimicrobials for the treatment of drug-resistant Acinetobacter baumannii pneumonia in critically ill patients: a systematic review and Bayesian network meta-analysis. Crit Care. 2017;21(1):319. doi:10.1186/s13054-017-1916-6
7. Nguyen M, Joshi SG. Carbapenem resistance in Acinetobacter baumannii and its importance in hospital-acquired infections. J Appl Microbiol. 2021;131(6):2715–2738. doi:10.1111/jam.15130
8. Veeraraghavan B, Shin E, Bakthavatchalam YD, et al. Microbiological and structural analysis of sulbactam/durlobactam and imipenem interaction with PBPs of Acinetobacter spp. Antimicrob Agents Chemother. 2025;69(4):e01627-24. doi:10.1128/aac.01627-24
9. Salman MF, Al-Mudallal NH, Ahmed ME. Cytotoxic effect of biogenic selenium nanoparticles using bacteriocin of Acinetobacter baumannii isolated from burns and wound infections. Iraqi J Sci. 2025;66(4):13. doi:10.24996/ijs.2025.66.4.13
10. Salman MF, Ahmed MEN. Effect of selenium nanoparticles on MexB gene
expression in Pseudomonas aeruginosa isolated from wound and burn infections. Iraqi
J Med Sci. 2024;22(1):79–92. doi:10.22578/IJMS.22.1
11. Romi ZM, Ahmed ME. Influence of biologically synthesized copper nanoparticles on biofilm produced by Staphylococcus haemolyticus isolated from seminal fluid. Iraqi J Sci. 2024;65:1948–1968.
12. Ahmed ME, Alzahrani KK, Fahmy NM, et al. Colistin-conjugated selenium nanoparticles: a dual-action strategy against drug-resistant infections and cancer. Pharmaceutics. 2025;17(5):556. doi:10.3390/pharmaceutics17050556
13. Ahmed ME, Sulaiman GM, Hasoon BA, et al. Green synthesis and characterization of apple peel-derived selenium nanoparticles and their antifungal activity and effects on MexA gene expression in Acinetobacter baumannii. Appl Organomet Chem. 2024:e7805. doi:10.1002/aoc.7805
14. Navidifar T, Amin M, Rashno M. Effects of sub-inhibitory concentrations of meropenem and tigecycline on biofilm-related gene expression in Acinetobacter baumannii. Infect Drug Resist. 2019;12:1099–1111. doi:10.2147/IDR.S199993
15. Yousefi Nojookambari N, Eslami G, Sadredinamin M, et al. Effects of sub-MIC colistin on biofilm formation and epithelial cell invasion of Acinetobacter baumannii. Microbiol Spectr. 2024;12(2):e02523-23. doi:10.1128/spectrum.02523-23
16. Mumtaz A, Saleem U, Arif M, Batool N. Antibiotic resistance and biofilm formation of Acinetobacter baumannii isolated from urinary catheters. Pak J Med Sci. 2024;40(11):2643. doi:10.12669/pjms.40.11.8754
17. World Health Organization. WHO bacterial priority pathogens list 2024. Geneva: WHO; 2024.
18. Chotiprasitsakul D, Ao-udomsuk K, Santinirand P. Impact of COVID-19 on epidemiology and mortality of carbapenem-resistant Acinetobacter baumannii bloodstream infections. J Glob Antimicrob Resist. 2025;43:155–161.
19. Borcan AM, Rotaru E, Caravia LG, et al. Trends in antimicrobial resistance of Acinetobacter baumannii from bloodstream infections. Pharmaceuticals. 2025;18(7):948. doi:10.3390/ph18070948
20. Kim SY, Cho SI, Bang JH. Risk factors for bloodstream infection in patients colonized with multidrug-resistant Acinetobacter baumannii. Am J Infect Control. 2020;48(5):581–583. doi:10.1016/j.ajic.2019.07.025
21. Kannan KP, Smiline Girija AS, Priyadharsini JV. Antimicrobial resistance and biofilm-associated virulence in multidrug-resistant Acinetobacter baumannii. Biochem Biophys Res Commun. 2025;780:152487. doi:10.1016/j.bbrc.2025.152487
22. Goncalves EK, Penwell WF, Fiester SE. Combating the growing threat of Acinetobacter baumannii resistance. Antibiotics (Basel). 2025;14(7):694. doi:10.3390/antibiotics14070694
23. Yu Z, Fu H, Zhou Y, et al. Molecular and biofilm characterization of Acinetobacter baumannii isolated from a neonatal intensive care unit. Front Cell Infect Microbiol. 2025;15:1705282. doi:10.3389/fcimb.2025.1705282
24. Nosair AM, Abdelaziz AA, Abo-Kamar AM, et al. Staphyloxanthin-encapsulated niosomal nanovesicles attenuate biofilm formation and meropenem persistence in Acinetobacter baumannii. BMC Microbiol. 2025;25(1):791. doi:10.1186/s12866-025-04507-1