In vitro bactericidal activity of blue light (465 nm) phototherapy on meticillin-susceptible and meticillin-resistant Staphylococcus pseudintermedius

Development of bacteriostatic central venous port using photobiomodulation: a comparative in vitro study

Photobiomodulation (PBM) occurs when a cell is exposed to low energy intensities. A novel central venous port (CVP) with light-emitting diodes (LEDs) that emits red light with a wavelength of 680 nm via wireless energy transmission technology has been established. This comparative in vitro study examined whether PBM can reduce the growth of methicillin-resistant Staphylococcus aureus (MRSA), a common cause of central venous (CV) infections, in vitro. In this comparative in vitro study, the red light with a wavelength of 680 nm was used to irradiate an MRSA suspension in phosphate-buffered saline for 7.5, 15, 30, or 60 min in a 3.5 cm Petri dish with an area of 8.5 cm2. The total energy was 85 J at 7.5 min, 170 J at 15 min, 340 J at 30 min, and 680 J at 60 min. Six dishes for each time and 6 temperature-controlled samples were prepared. Each sample was incubated overnight at 37℃. The Shapiro-wilk test was used to determine whether the data were normally distributed. The numbers of colonies were counted and compared using one-factor ANOVA and Bonferroni's post-hoc test. The mean numbers of colonies in the control group were 60.3, where the numbers of colonies in the irradiated group were 51.4 at 7.5 min, 53.5 at 15 min, 44.6 at 30 min, 34.3 at 60 min. The mean number of colonies in the 60 min irradiated group differed significantly from that in the control, 7.5 min, and 15 min groups. The Bonferroni's post-hoc test showed significant difference in the number of colonies between control vs. 30 min control vs. 60 min, 7.5 min vs. 60 min, 15 min vs. 60 min. PBM with 680 nm LEDs on MRSA for 340 J at 30 min and 680 J at 60 min inhibited the growth of cell colonies. These findings support the use of photobiomodulation in Central venous port to prevent CV access port-Blood stream infection.

Antimicrobial Strategies Proposed for the Treatment of S. pseudintermedius and Other Dermato-Pathogenic Staphylococcus spp. in Companion Animals: A Narrative Review

The treatment of dermato-pathogenic Staphylococcus spp., particularly Staphylococcus pseudintermedius, in companion animals presents significant challenges due to rising antimicrobial resistance. This review explores innovative strategies to combat these infections. We examined novel antimicrobials and the repurposing of existing drugs to enhance their efficacy against resistant strains. Additionally, we evaluate the potential of natural products, nanomaterials, and skin antiseptics as alternative treatments. The review also investigates the use of antimicrobial peptides and bacteriophages, highlighting their targeted action against staphylococcal pathogens. Furthermore, the role of adjuvants in antibiotic treatments, such as antimicrobial resistance breakers, is discussed, emphasizing their ability to enhance therapeutic outcomes. Our analysis underscores the importance of a multifaceted approach in developing effective antimicrobial strategies for companion animals, aiming to mitigate resistance and improve clinical management of staphylococcal skin infections.

In vitro evaluation of bactericidal effects of fluorescent light energy on Staphylococcus pseudintermedius and S. aureus

BACKGROUND

Staphylococcus pseudintermedius and S. aureus are bacterial species of importance in veterinary medicine. The increasing incidence of antibiotic resistance necessitates the implementation of novel treatment modalities. Fluorescent light energy (FLE) is used as an adjunctive and primary treatment for canine pyoderma. However, no in vitro studies exist investigating its bactericidal effects against S. pseudintermedius or S. aureus.

OBJECTIVES

To determine the bactericidal effects of FLE on S. pseudintermedius and S. aureus isolates.

MATERIALS AND METHODS

Two meticillin-susceptible S. pseudintermedius (MSSP) isolates, three meticillin-resistant S. pseudintermedius (MRSP) isolates and one meticillin-resistant S. aureus (MRSA) isolate were studied. A commercially available blue light-emitting diode (bLED) lamp and photoconverting hydrogel FLE system was used. All bacteria were exposed to five conditions following inoculation: (i) no treatment (control); (ii) blue light (bLED) once; (iii) bLED twice consecutively; (iv) FLE (bLED and photoconverting hydrogel) once; and (v) FLE (bLED and photoconverting hydrogel) twice consecutively. Each individual exposure was 2 min long.

RESULTS

No statistically significant differences (p < 0.05) were found for any treatment group when each bacterial isolate was evaluated individually, MSSP isolates were grouped, MRSP isolates were grouped, when all S. pseudintermedius isolates were combined, or when all isolates of both Staphylococcus species were combined.

CONCLUSIONS AND CLINICAL RELEVANCE

While clinical success is reported when using FLE to treat Staphylococcus infections in animals, no in vitro antibacterial efficacy was identified for S. pseudintermedius or S. aureus under experimental conditions. The clinical success observed with FLE may be the result of a more complex in vivo response.

Fluorescent Light Energy in the Management of Multi Drug Resistant Canine Pyoderma: A Prospective Exploratory Study

The increase in prevalence of staphylococcal antimicrobial resistance has been also associated with pyoderma in dogs, and prolonged antibiotic treatment, as often needed in severe cases of pyoderma, has been related to influencing possible development of multidrug resistance (MDR). Fluorescent light energy (FLE) has been indicated to improve pyoderma lesions as adjunct therapy to systemic antibiotics. In the present study, we evaluated the effect of FLE on clinical signs of MDR canine deep pyoderma (CDP) and interdigital furunculosis (CIF) when administered as solely management. Sixteen client-owned dogs affected by CIF (five dogs) and CDP (eleven dogs) were scored using a dedicated scoring system and received a single FLE applications twice weekly, until clinical resolution was achieved. Mean time to achieve complete resolution was 5.20 ± 3.56 weeks (median 3 weeks) for CIF cases and 4.18 ± 1.47 weeks (median 4 weeks) for CDP ones. FLE shows promise as an aid to managing clinical signs while reducing reliance on antibiotics for MDR CDP and CIF. In this study, FLE was responsible for the decrease in lesion scores and resolution of MDR pyoderma infection without any adjunct therapy, having a potential useful role to play in antibiotic stewardship programs, efficiently promoting complete clinical resolution of MDR lesions while optimizing the use of antibiotics.

Characterization of Blue Light Treatment for Infected Wounds: Antibacterial Efficacy of 420, 455, and 480 nm Light-Emitting Diode Arrays Against Common Skin Pathogens Versus Blue Light-Induced Skin Cell Toxicity

Objective: To determine effective treatment strategies against bacterial infections of chronic wounds, we tested different blue light (BL)-emitting light-emitting diode arrays (420, 455, and 480 nm) against wound pathogens and investigated in parallel BL-induced toxic effects on human dermal fibroblasts. Background: Wound infection is a major factor for delayed healing. Infections with Pseudomonas aeruginosa and Staphylococcus aureus are clinically relevant caused by their ability of biofilm formation and their quickly growing antibiotics resistance. BL has demonstrated antimicrobial properties against various microbes. Methods: Determination of antibacterial and cell toxic effects by colony-forming units (CFUs)/biofilm/cell viability assays, and live cell imaging. Results: A single BL irradiation (180 J/cm²), of P. aeruginosa at both 420 and 455 nm resulted in a bacterial reduction (>5 log₁₀ CFU), whereas 480 nm revealed subantimicrobial effects (2 log₁₀). All tested wavelengths of BL also revealed bacteria reducing effects on Staphylococcus epidermidis and Escherichia coli (maximum 1-2 log₁₀ CFU) but not on S. aureus. Dealing with biofilms, all wavelengths using 180 J/cm² were able to reduce significantly the number of P. aeruginosa, E. coli, and S. epidermidis. Here, BL_420nm achieved reductions up to 99%, whereas BL_455nm and BL_480nm were less effective (60-83%). Biofilm-growing S. aureus was more BL sensitive than in the planktonic phase showing a reduction by 63-75%. A significant number of cell toxic events (>40%) could be found after applying doses (>30 J/cm²) of BL_420nm. BL_455nm showed only slight cell toxicity (180 J/cm²), whereas BL_480nm was nontoxic at any dose. Conclusions: BL treatment can be effective against bacterial infections of chronic wounds. Nevertheless, using longer wavelengths >455 nm should be preferred to avoid possible toxic effects on skin and skin cells. To establish BL therapy for infected chronic wounds, further studies concerning biofilm formation and tissue compatibility are necessary.

Current Applications and Future Perspectives of Fluorescence Light Energy Biomodulation in Veterinary Medicine

The purpose of this review is to determine the state of the art of the mode of action and potential applications of fluorescence photobiomodulation in veterinary medicine. After a summary of the assets that have led the translation of such light-based therapies from bench side into clinical use, recent advances in canine dermatology using this brand-new approach are presented, and future scenarios where this type of care may provide benefits over the current standard care are highlighted.

Is low-level laser therapy useful as an adjunctive treatment for canine acral lick dermatitis? A randomized, double-blinded, sham-controlled study

BACKGROUND

Conventional therapy for canine acral lick dermatitis (ALD) consists of systemic antibiotics and anti-anxiety medications. Low-level laser therapy (LLLT) is a noninvasive therapy used to treat inflammatory and painful conditions.

HYPOTHESIS/OBJECTIVES

The primary objective was to determine whether LLLT with conventional therapy would be beneficial as an adjunct treatment for ALD. We hypothesized that LLLT and conventional therapy combined would result in a greater reduction in licking Visual Analog Score (LVAS) compared to conventional therapy alone. Secondary objectives were to assess change in lesion/ulcer size, thickness and hair growth.

ANIMALS

Thirteen dogs with a skin lesion consistent with ALD.

METHODS AND MATERIALS

Dogs were randomly assigned to two groups. All dogs received systemic antibiotics and trazodone. The treatment group (TG) received LLLT by laser (130 mW, 2 min) with blue and red light-emitting diodes (LEDs), while the control group (CG) had sham therapy (laser/LEDs off). Treatments were administered three times weekly for two weeks, then twice weekly for two weeks for a total of 10 visits. Descriptive statistics were performed (mean, median); primary and secondary objectives were assessed with nonparametric ANOVA (Kruskal-Wallis test), with significance set at P < 0.05.

RESULTS

Thirteen dogs (six CG, seven TG) were enrolled. There were no significant differences in median LVAS, lesion/ulcer size or thickness of the ALD lesion between TG and CG. There was a significantly greater increase (24%) in hair growth in TG (P = 0.0081) compared to CG.

CONCLUSIONS AND CLINICAL RELEVANCE

Treatment of ALD requires multimodal therapy. Although combining LLLT with conventional therapy did not result in a significantly greater reduction in LVAS, there was a significant increase in hair growth compared to conventional therapy alone.

Fluorescence biomodulation in the management of canine interdigital pyoderma cases: a prospective, single-blinded, randomized and controlled clinical study

BACKGROUND

Interdigital pyoderma is a common multifactorial, inflammatory disease of the canine interdigital skin. Lesions commonly become infected secondarily. In addition to management of the underlying cause, management of the chronic inflammatory changes in the interdigital skin created by secondary infection and by the release of keratin into deep tissues is required. Fluorescence biomodulation appears to modulate the inflammatory process in dermatological disorders and has shown promise in preliminary studies evaluating its use in superficial and deep pyoderma in dogs.

HYPOTHESIS/OBJECTIVES

To evaluate the effect of a fluorescence biomodulation (FB) system used in conjunction with systemic antibiotic on clinical manifestations of canine interdigital pyoderma (CIP), compared to dogs treated with antibiotic alone.

ANIMALS

Thirty-six dogs diagnosed with CIP.

METHODS AND MATERIALS

Dogs were randomly allocated to treatment groups of either antibiotic alone (Group A) or antibiotic plus twice-weekly FB application (Group B). Dogs were scored over a 12 week period on the basis of two measured parameters: a global lesion score composed of four different lesions types and neutrophil engulfing bacterial scores.

RESULTS

A statistically significant decrease was seen by Week 3 in both measured parameters for Group B compared to Group A. The mean time-to-resolution of lesions was 4.3 weeks in Group B and 10.4 weeks in Group A.

CONCLUSION AND CLINICAL IMPORTANCE

The FB system shows promise as an adjunct therapy to systemic antibiotic use in the management of CIP.

In vitro bactericidal activity of 465-470 nm blue light phototherapy and aminolevulinic acid on Staphylococcus pseudintermedius

BACKGROUND

Staphylococcus pseudintermedius is the principal pathogen causing bacterial skin infections in dogs. Photodynamic therapy (PDT) involving the combination of light and a topical photosensitizer is used to treat human skin infections. Although the antimicrobial effects of PDT have been demonstrated using in vivo and in vitro studies in humans, its effects on dogs and their pathogens are unclear.

OBJECTIVES

The aim of this study was to demonstrate the in vitro efficacy of PDT over a 465-470 nm spectrum to kill S. pseudintermedius using δ-aminolevulinic acid (ALA) as the photosensitizer.

METHODS

Six S. pseudintermedius isolates from canine skin were exposed to blue light-emitting diodes (LEDs) at 465-470 nm, with or without ALA. The light doses were 18.4, 36.8 and 55.2 J/cm2 . The number of colony-forming units and optical densities of broth cultures were measured and then compared with Dunnett's test. Bacterial viability was monitored using fluorescence microscopy and the fluorescence intensity values were compared with a paired Student's t-test.

RESULTS

Blue light inhibited the growth of S. pseudintermedius; the effect significantly increased with the addition of ALA as a photosensitizer and with increasing light doses. Live/dead staining confirmed that PDT reduced bacterial viability and exerted an antibacterial effect.

CONCLUSION AND CLINICAL IMPORTANCE

Blue light has a strong antibacterial effect on S. pseudintermedius in a light dose-dependent manner. ALA alone did not exhibit bactericidal action, but its combination with blue light increased the effect of PDT compared to blue light alone.

Antimicrobial blue light inactivation of pathogenic microbes: State of the art

As an innovative non-antibiotic approach, antimicrobial blue light in the spectrum of 400-470nm has demonstrated its intrinsic antimicrobial properties resulting from the presence of endogenous photosensitizing chromophores in pathogenic microbes and, subsequently, its promise as a counteracter of antibiotic resistance. Since we published our last review of antimicrobial blue light in 2012, there have been a substantial number of new studies reported in this area. Here we provide an updated overview of the findings from the new studies over the past 5 years, including the efficacy of antimicrobial blue light inactivation of different microbes, its mechanism of action, synergism of antimicrobial blue light with other angents, its effect on host cells and tissues, the potential development of resistance to antimicrobial blue light by microbes, and a novel interstitial delivery approach of antimicrobial blue light. The potential new applications of antimicrobial blue light are also discussed.