To our knowledge, only a few studies have examined the development of cross-tolerance to different PS following repeated sublethal doses of aPDT. Initial aPDT treatments are resumed in Table 2.
Table 2. Summary of the reviewed studies investigating the cross-tolerance with other PS.
aPDT Conditions | Targeted microorganism(s) | Observation(s) | Reference |
RB, LED, 515 nm, 5 cycles | S. aureus | No cross tolerance to structurally different PS, NMB, and increased sensitivity to TMPyP | |
RB, LED, 515 nm, 10 cycles | S. agalactiae | No cross-tolerance to structurally different PS, NMB, and ZnPc | |
MB, fluorescent lamps, 575-700 nm, 7 cycles | S. aureus | Cross-tolerance to previously effective structurally similar PS TBO | |
Abbreviations: Cur: curcumin; LED: light-emitting diode; MB: methylene blue; NMB: new methylene blue; RB: rose bengal; TBO: toluidine blue; TMPyP: 5,10,15,20-tetrakis (1-methyl-4-pyridinium) porphyrin tetra(p-toluenesulfonate); ZnPc: zinc phthalocyanine. | |||