4.2. Chlorhexidine and Antibiotic Susceptibility Test

The clinical strains P. aeruginosa (PACL, PA1, PA2, PA4, PA5, PA6, PA7, PA9, PA10, PA11, PA12, PA13, and PA14) were isolated from the patients in the King Chulalongkorn Memorial Hospital, Bangkok, Thailand as approved by the Institutional Review Board of the Faculty of Medicine, Chulalongkorn University (IRB 610/2564) and the Institutional Biosafety Committee (MDCU-IBC001/2022). The minimal inhibitory concentrations (MICs) against Chlorhexidine digluconate (Sigma-Aldrich, Darmstadt, Germany), colistin (Sigma-Aldrich), imipenem (Siam Pharmaceutical, Bangkok, Thailand), meropenem (Pfizer, NY, USA), and tobramycin (Novartis, Basel, Switzerland) were evaluated by the broth microdilution method using cation-adjusted Mueller–Hinton broth (BBL, MD, USA) as recommended by the Clinical and Laboratory Standards Institute (CLSI) guidelines [60]. Briefly, serial dilutions of these agents were prepared in 96-well culture plates, followed by inoculation of P. aeruginosa isolates (final concentration 1 × 10⁵ CFU/well) and incubation at 37 °C for 18 h. The MICs, the lowest concentration that can inhibit bacterial growth, and the susceptibility test were visually evaluated following the CLSI guidelines (Supplementary Table S4).