Figure 5.
Antimicrobial photodynamic inactivation of clinical isolates of K. pneumoniae. (A) Growth inhibition of 118 clinical isolates of K. pneumoniae subjected to antimicrobial photodynamic inactivation (aPDI) with PSIR-3. The bacteria were used at a concentration of 1 × 107 CFUs/mL and mixed in triplicate with 4 mg/L of PSIR-3 or PSIR-4 compounds. For the aPDI, the mixture of bacteria with PS was exposed for 1 h at 17 µW/cm2 of white light. As a control, bacteria combined with the photosensitizers (PSs) not exposed to light (PSIR-3 or PS-Ru) and bacteria not combined with the PSs (control) were included. Colony count enumerated of viable bacteria on ca-MH agar after serial micro-dilution. The CFUs/mL values are presented as means ± SD on a log10 scale. (B) From the clinical isolates, 66 ESBL-producing bacteria were exposed to aPDI, using PSIR-3 or PS-Ru, and MIC for cefotaxime (Cfx) was performed in triplicate, in ca-MH broth, for 16–20 h. (C) For ESBL-producing bacteria, the MIC for PSIR-3 or PS-Ru, were determined in combination with 4 mg/L of Cfx, performed in triplicate in ca-MH agar for 16–20 h. The MIC values are presented as median ± SD of mg/mL on a log2 scale. Not significant (ns) p > 0.05 by Student’s t-test among treated bacteria compared to control; **** p < 0.0001 by Student’s t-test among treated bacteria compared to control.