Effect of photodynamic therapy on clinical isolates of Staphylococcus spp

Abstract

Staphylococcus spp. are opportunistic microorganisms known for their capacity to develop resistance against antimicrobial agents. The objective of this study was to evaluate the effect of photodynamic therapy (PDT) on 20 Staphylococcus strains isolated from the human oral cavity, including S. aureus, S. schleiferi, S. epidermidis, S. capitis, S. haemolyticus, and S. lentus. A suspension of each Staphylococcus strain (10 6 cells/ mL) was submitted to PDT using methylene blue and a low power laser. The isolated effects of methylene blue, laser treatment and ciprofloxacin were also evaluated. After the experimental treatments, 0.1 mL aliquots of the suspensions were seeded onto BHI agar for determination of the number of colony-forming units (CFU/mL). The results were analyzed by analysis of variance and Tukey's test (p ≤ 0.05). The mean reduction in bacterial counts of the strains submitted to PDT ranged from 4.89 to 6.83 CFU (log 10 )/mL, with the observation of a decreasing susceptibility to treatment of S. schleiferi, S. haemolyticus, S. epidermidis, S. capitis, S. aureus, and S. lentus. The results showed that PDT was effective in reducing the number of viable cells of all clinical Staphylococcus isolates studied.

Comparative study between photodynamic and antibiotic therapies for treatment of footpad dermatitis (bumblefoot) in Magellanic penguins (Spheniscus magellanicus)

“…The findings of the in vitro resistance test for PDT corroborate other studies in the literature that show that PDT is capable of destroying resistant microorganisms even after prolonged use of antibiotics [21,22]. However, it is well established that susceptibility of microorganisms to PDT is dependent on several factors such as concentration of photosensitizer, pre-irradiation time, kind of microorganism, and irradiation time.…”

Innovative Strategies to Overcome Biofilm Resistance

“…We obtained the same results for the eradication of S. aureus with a light dose of 12 J/cm 2 , whether the irradiation time was 10 or 60 min (data not shown). To inactivate clinical isolates of Staphylococcus species, Miyabe et al used 3 mM MB and a light fluence of 26.3 J/cm 2 (gallium-aluminum-arsenide laser, 660 nm) to obtain a mean reduction of 6.29 log 10  cfu/mL [56]. In S. mutans, Rolim et al did not observe photodynamic activity when MB was used at a concentration of 163.5  μ M at 24 J/cm 2 (LED, 640 nm), but a significant reduction (3 log 10  cfu/mL) was observed when the same concentration of TBO and an equal light dose were used [57].…”

Study of Methylene Blue Ototoxicity in the Guinea Pig

“…In fact, it has been shown to significantly eradicate Staphylococcus sp [14, 23, 24], Pseudomonas sp 6 , or Candida sp [25]. Many studies have also shown the efficacy of PDT using in vivo models.…”