Determination of the antibacterial efficacy of a new porphyrin-based photosensitizer against MRSA ex vivo

Abstract

Following extensive in vitro screening of new photosensitizers the purpose of the present study was to examine penetration as well as antibacterial efficacy of a lead photosensitizer against MRSA using an ex vivo porcine skin model. Two different applications were performed: (i) preincubation of bacteria in solution with a porphyrin-based photosensitizer XF73 and subsequent application on the ex vivo porcine skin; (ii) application of pure bacteria on the explants followed by an incubation with XF73 in a water-ethanol formulation for up to 60 min under occlusion. The localisation of XF73 was restricted to the stratum corneum. Different concentrations (0-10 microM) of XF73 and different incubation times (5-60 min) were used to determine phototoxicity against methicillin-resistant and methicillin-sensitive S. aureus, which was applied on the explants. Preincubation of S. aureus with 0.1 microM XF73 in solution prior to the application of these XF73-incubated bacteria on the skin demonstrates a higher efficacy (>3 log10) after irradiation. Antibacterial photodynamic inactivation resulted in a approximately 1 log10 (0.1 microM)-3.64+/-0.035 (10 microM) log10 growth reduction independently of the antibiotic resistance pattern of used S. aureus strains. Irradiation of applied bacteria without photosensitizer incubation did not show any marked decrease (<1 log10) of bacteria cell number, indicating a significant phototoxicity of the XF73. Histological evaluations of untreated and treated skin areas upon irradiation within 24 h showed no significant degree of necrosis or apoptosis determined by TUNEL-assay indicating that the porcine skin is still vital. This study demonstrates that this XF73 porphyrin-based photosensitizer had concentration-dependent differences in killing efficacy of MRSA in comparison to skin cells using an ex vivo porcine skin model. The results described here imply that topical delivery of XF73 may be considered as a possible treatment in patients with superficial infections of the skin.

Decolonisation of MRSA, S. aureus and E. coli by Cold-Atmospheric Plasma Using a Porcine Skin Model In Vitro

“…For each skin sample a cotton-tipped rod was moistened in sampling buffer (0.1% Tween80, 0.0075 M phosphate puffer, pH 7.9) before swabbing the entire surface three times. First the recovery efficacy was tested to establish the range of viable numbers of CFU per ml of untreated skin samples, which was in accordance with already published data [16]. A reproducible correlation between three swabbing steps and the recovery efficiency of bacteria applied to the skin could be evaluated (data not shown).…”

“…The preparation was done as already published [16]. Briefly, the excised skin was washed with water, epilated with a dry razor and the adipose tissue beneath the dermis was removed with a scalpel.…”

“…For demonstrating the killing efficacies of new disinfecting agents an ex vivo porcine skin model was developed in our lab [16]. This model was used, as it serves as an alternative skin model for human skin based on many similarities regarding behaviour, composition, histological, physiological and permeability properties [17], [18].…”

Photodynamic Antimicrobial Chemotherapy (PACT) in osteomyelitis induced by Staphylococcus aureus: Microbiological and histological study

“…A previous study [26] has suggested that the use of PACT seems to be a practical alternative for treating osteomyelitis. However, factors such as the pharmacokinetics of the PS, the use of an adequate wavelength and both irradiation and incubation protocols may affect the outcome of the procedure.…”

All you need is light

“…[148][149][150] XF73, a cationic porphyrin PS, is able to reduce MRSA growth by >3 log 10 in a porcine skin infection model. 151 PDT with polycationic PS conjugates and 665 nm light in murine excisional wounds led to a reduction in infectious organisms, permitting mouse survival to reach 90%, and reduce substantially pathogen viability. 152 TBO and light cured mice of otherwise fatal Vibrio vulnificus wound infections in murine models.…”