Hydrochloric Acid Lock Therapy for Catheter-Related Bloodstream Infections: In Vitro Antimicrobial Activity and Catheter Material Compatibility

Catheter-related bloodstream infections (CRBSIs) are frequently caused by biofilm-forming bacteria that are difficult to eradicate with antibiotics. In Denmark, hydrochloric acid lock therapy (HALT) has been used for more than a decade with reported success in catheter salvage, but its antimicrobial efficacy and potential impact on catheter materials remain insufficiently studied in vitro. This study evaluated the efficacy of hydrochloric acid (HCl) against biofilms of Staphylococcus aureus, Pseudomonas aeruginosa, and Staphylococcus epidermidis, and assessed its effects on silicone and polyurethane central venous catheters. Biofilms grown in microtiter well plates and on catheter segments were exposed to three 10-min treatments with 2 M HCl or 0.9% saline. Biofilm-free catheters received the same exposures as the biofilm samples before mechanical testing. HCl markedly reduced bacterial viability, achieving mean reductions of 5.4 log₁₀ colony-forming units (CFU)/mL in well plates and 4.1 log₁₀ CFU/mL on catheters. No bacterial growth was detected on catheter segments following HCl treatment. Tensile strength testing and optical microscopy revealed no evidence of compromised mechanical integrity or surface alterations in either catheter type following HCl exposure. Overall, HCl demonstrated strong antimicrobial activity without compromising catheter integrity, supporting further investigation of HALT as an adjunct to systemic antibiotics for managing CRBSIs.