Antimicrobial photodynamic therapy can be an effective adjuvant for surgical wound healing in cattle

BACKGROUND

Rumenostomy is a useful procedure commonly performed in cattle for medical treatment of domestic ruminants with forestomach diseases. Methylene blue (MB)-mediated antimicrobial photodynamic therapy (APDT) has been broadly investigated to treat infected wounds.

AIM

The aim of the study was to evaluate the effectiveness of MB-mediated APDT (MB-APDT) combined with chlorhexidine and zinc oxide ointment on wound healing process after rumenostomy.

METHODS

Fourteen Nelore bulls were subjected to rumenostomy procedure. Animals were randomly divided into MB-APDT (MB associated with a red diode laser performed immediately after surgery and repeated on days 3, 5, 7 and 10) and control groups. Daily care included topical cleaning with chlorhexidine 2% followed by topical zinc oxide ointment. Animals were followed-up until the 28th day.

RESULTS

Wounds presented a better post-surgical profile in MB-APDT group when it was compared with the control group. In MB-APDT group, it was also possible to observe less pain on palpation of wounds borders, less edema and inflammatory exudate. Additionally, animals from MB-APDT group were faster discharged from the cattle care facility.

CONCLUSION

Our results support the use of MB-APDT for the post-surgical management of rumenostomy. This pilot study ratifies the use of APDT in cattle and also suggests that it could be performed for other surgical procedures as a complementary approach or an alternative for topical administration of antibiotics.

Antimicrobial Blue Light: An Alternative Therapeutic for Multidrug-Resistant Gonococcal Infections?

Gonorrhea is the second most prevalent sexually transmitted infection globally. Neisseria gonorrhoeae, the etiological agent of gonorrhea, is evolving into a superbug and may become untreatable due to its resistance to almost all the antibiotics available. There is a critical need for the development of alternative therapeutics. This pilot study aimed to investigate the potential of an innovative non-antibiotic approach, antimicrobial blue light (aBL), as an alternative therapeutic for gonococcal infections. We studied one ATCC strain (ATCC 700825) and one multidrug-resistant clinical strain of N. gonorrhoeae. The results demonstrated that both the strains are highly susceptible to aBL at 405nm. In planktonic suspensions, an exposure of 45 J/cm² aBL reduced the survival fraction of colony-forming units (CFU) by 7.16-log₁₀ for ATCC 700825 and 2.48-log₁₀ for the clinical strain. When the aBL exposure was further increased to 54 J/cm², a complete eradication of CFU (over 8-log₁₀ CFU reduction) was achieved for ATCC 700825 and a reduction of 5.43-log₁₀ CFU was obtained for the clinical strain. In addition, we observed that singlet oxygen plays a vital role in the antimicrobial effect of aBL on N. gonorrhoeae. In conclusion, the results of this pilot study suggest that aBL is a promising approach to combat gonococcal infections. Further studies are warranted in the analysis of the endogenous photosensitizers in N. gonorrhoeae cells, evaluation of the aBL efficacy against gonococcal infections in animal models, and investigation of the mechanism of action of aBL.

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.