The synergistic antimicrobial effect of tetrasodium EDTA and chlorhexidine against Enterobacterales isolates from hospital carriers

BACKGROUND: Hospital-acquired infections are a major concern in healthcare settings, often involving Gram-negative bacilli that affect both patients and healthcare personnel. This study aimed to assess the antimicrobial effects of chlorhexidine and EDTA, alone and in combination, on Gram-negative bacilli isolated from carriers, along with their antibiotic resistance profiles and biofilm-forming abilities. METHODS: This cross-sectional study collected 390 samples from hospital personnel, patients and environmental surfaces to investigate Gram-negative bacilli. Antibiotic susceptibility, biofilm formation, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of chlorhexidine, with and without EDTA, were also determined. PCR also was used to detect biocide resistance genes (qacE, qacEΔ1, CepA). RESULTS: A total of 120 Gram-negative bacilli were isolated and subsequently confirmed through biochemical tests. Klebsiella pneumoniae was the predominant bacterial species, accounting for 70% (n=84). Based on the present findings, 29 (24.1%) isolates were multidrug-resistant (MDR). ESBL and AmpC production were detected in 12.5% and 21% of isolates, respectively. Strong biofilm formation was observed in 58.3% of the samples. Chlorhexidine alone inhibited bacterial growth at a MIC₉₀ of 0.009%, with a bactericidal effect at 0.019%. When combined with EDTA, a synergistic effect was observed, reducing the MIC to 0.002% and the MBC to 0.004%, indicating enhanced antimicrobial activity (P ≤ 0.05). CONCLUSIONS: These findings indicate a considerable prevalence of antibiotic-resistant and biofilm-producing Gram-negative bacilli among carriers. Furthermore, the increased activity observed with the combination of chlorhexidine and EDTA suggests that this approach may represent a potentially useful option for decontamination and infection control in healthcare settings.