In a range of bacterial pathogens, Mn is recognized as having a major effect on virulence [10, 11]. Apart from participating in several enzyme functions, Mn complexes with phosphate and lactate were demonstrated to scavenge
ROS . The role of Sod in the pathogenesis of many bacteria was proved. In S. aureus however, the results are not unambiguous. The very first analyses of antioxidant enzymes and staphylococcal virulence showed no correlation . Similarly, in a mouse abscess model resulting from S. aureus infection, inactivation of sodA gene, recognized as the main Sod activity in S. aureus, had no impact on staphylococcal virulence . Moreover, mouse kidney infection was not attenuated after sodM gene inactivation . On the other hand, examination of a range of virulent versus non-virulent PFT�� S. aureus clinical isolates, showed statistically significant higher Sod activity in the first group studied . Karavolos et al. tested the role of Sod in a mouse subcutaneous model of infection and claimed that mutants deprived of either SodA, SodM or both activities had significantly reduced virulence compared to
S. aureus wild-type SH1000 strain . As bacteria replicate very quickly, the possibility selleck chemical of mutant selection which effectively deals with antibiotic treatment rises. An alarming increase in antibiotic resistance spreading among pathogenic bacteria inclines to search for alternative therapeutic options, for which resistance
cannot be developed easily. One such option is photodynamic inactivation of bacteria (PDI). This method involves the use of non toxic dyes, so called photosensitizers (PS), which become excited upon visible light of an appropriate wavelength and eventually a number of ROS are formed . As a consequence of ROS action, which are known to cause severe damage to DNA, RNA, proteins, and lipids, bacterial cells die. Two oxidative mechanisms can occur after light activation of a photosensitizer. When the photosensitizer interacts with a biomolecule, free radicals (type I mechanism), and/or singlet molecular oxygen (1O2) (type Celecoxib II mechanism) are produced, which are responsible for cell inactivation . In the case of porphyrin-based photosensitizers, 1O2 seems to be the main ROS generated upon photoexcitation, although O2 . -, .OH are also implicated . In a very elegant study by Hoebeke et al., the photochemical action of bacteriochlorin a, a structural analog of protoporphyrin IX, was also demonstrated to be based on both, type I and type II mechanism of action in a 1:1 proportion . Several lines of evidence indicate the effectiveness of PDI in vitro against both Gram-positive and -negative species [21, 22]. It was also demonstrated that photodynamic inactivation may be applied to inactivate bacterial virulence factors, which represents an advantage over topical antibiotic treatments .