Antimicrobial Efficacy of Multiwalled Carbon Nanotube Suspensions Against Multidrug-Resistant Stenotrophomonas maltophilia: A Comprehensive In Vitro Analysis

The emergence of multidrug-resistant (MDR) Stenotrophomonas maltophilia poses significant therapeutic challenges in clinical settings. This opportunistic gram-negative bacterium exhibits extensive antibiotic resistance mechanisms and forms biofilms on medical devices. Multiwalled carbon nanotubes (MWCNTs) have emerged as promising antimicrobial agents due to their unique physicochemical properties and multiple mechanisms of action.

Thirty clinical samples were collected from Kufa University Medical Center (November 2023-March 2024), yielding 20 confirmed S. maltophilia isolates through VITEK-2 identification. MWCNTs were synthesized via thermal decomposition and characterized using AFM, SEM, XRD, and FTIR. Antimicrobial activity was evaluated using well diffusion and broth microdilution methods at 25, 50, 75, and 100 μg/mL concentrations. Biofilm assays were performed using crystal violet staining. Results were compared with six conventional antibiotics.

MWCNT characterization revealed 82.74 ± 5.2 nm grain size with armchair geometry. MWCNT suspensions demonstrated concentration-dependent antimicrobial activity, with 100 μg/mL producing 22.7 ± 1.58 mm inhibition zones, exceeding most antibiotics except ciprofloxacin (25.1± 4.98 mm). MIC values were 18.4 ± 10.01 μg/mL (MIC₅₀ = 12.5 μg/mL). Biofilm formation was significantly reduced, with 100% MWCNT (The 100 μg/mL suspension) achieving 97.3% inhibition. All isolates exhibited high antibiotic resistance (75-95%).

The superior antimicrobial activity of MWCNTs demonstrates their potential as alternative therapeutic agents for MDR S. maltophilia infections. Multiple mechanisms, including physical membrane disruption, reactive oxygen species generation, and metabolic interference, explain effectiveness against resistant isolates. The exceptional biofilm inhibition addresses critical clinical challenges, as S. maltophilia biofilms are difficult to eradicate with standard antibiotics. Clinically achievable MIC values support therapeutic feasibility.

MWCNT suspensions possess potent antimicrobial activity against MDR S. maltophilia with superior biofilm inhibition properties. The ability to overcome resistance mechanisms suggests MWCNTs represent promising alternatives for treating S. maltophilia infections, warranting further safety evaluation and clinical development.