Effective Photodynamic Therapy with Ir(III) for Virulent Clinical Isolates of Extended-Spectrum Beta-Lactamase Klebsiella pneumoniae

Background: The extended-spectrum beta-lactamase (ESBL) Klebsiella pneumoniae is one of the leading causes health-associated infections (HAIs), whose antibiotic treatments have been severely reduced. Moreover, HAI bacteria may harbor pathogenic factors such as siderophores, enzymes, or capsules, which increase virulence these strains. Thus, new therapies, antimicrobial photodynamic inactivation (aPDI), are needed. Method: A collection 118 clinical isolates K. was characterized by susceptibility and through determination minimum inhibitory concentration (MIC) amikacin (Amk), cefotaxime (Cfx), ceftazidime (Cfz), imipenem (Imp), meropenem (Mer), piperacillin–tazobactam (Pip–Taz); and, PCR, frequency genes K2, magA, rmpA, entB, ybtS, allS. Susceptibility to innate immunity, human serum, macrophages, polymorphonuclear cells, tested. All strains were tested for sensitivity photosensitizer PSIR-3 (4 µg/mL) in a 17 µW/cm2 30 min aPDI. Results: significantly higher ESBL than non-ESBL observed. genotype K2+, ybtS+, allS+ display enhanced virulence, since they showed resistance well phagocytosis. susceptible aPDI with decreasing viability 3log10. combined treatment Cfx improved 6log10 synergistic, it fractional (FIC) index value 0.15. Conclusions: effectively inhibits pneumoniae, including riskier ESBL-producing genotype. synergistic Cfx.