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Methylene blue-mediated antimicrobial photodynamic therapy on chicken semen
G A Novaes1, M H Blank2, T M Yoshimura3
1Department of Animal Reproduction, College of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Av. Prof. Dr. Orlando Marques de Paiva, 87, CEP, SP 05508-900, Brazil; Cobb-Vantress Brasil Ltda., Guapiaçu, SP, Brazil.
Background:
Artificial insemination is widely employed in poultry, but high degrees of bacterial contamination are often observed in semen because of its passage through the cloaca. Consequently, most semen extenders for birds have antibiotics that could aggravate bacterial resistance.
Methods:
We evaluated the potential of antimicrobial photodynamic therapy (PDT) as an alternative to the use of antibiotics, and assessed whether changes in concentration and incubation time with methylene blue (MB), radiant exposure, and irradiance of light affect spermatozoa activity and bacteria in chicken semen.
Results:
Incubation with MB (< 25 µM) did not alter sperm motility, regardless of the pre-irradiation time (PIT, 1 or 5 min). Following 1 min of PIT with MB at 10 µM, samples were irradiated for 30, 60, 120, and 180 s at irradiances of 44, 29, and 17 mW/ cm² (660 nm LedBox). MB and light alone did not interfere with the analyzed parameters. However, when both factors were associated, increases in light dose led to greater reductions in sperm parameters, regardless of the irradiance used. Besides, PDT conditions that were less harmful to spermatozoa were not able to significantly reduce bacterial colonies in chicken semen.
Conclusions:
A failure in MB selectivity could explain unsuccessful bacterial reduction following PDT. Further research involving other photosensitizers or conjugating molecules to MB to target microbial cells is needed for PDT application in poultry breeders.
Insights
Antimicrobial photodynamic therapy (PDT) using methylene blue (MB) did not effectively reduce bacteria in chicken semen without harming spermatozoa. Further research is needed to develop selective photosensitizers for poultry artificial insemination.
Area of Science:
- Veterinary Science
- Photodynamic Therapy
- Microbiology
Background:
- Bacterial contamination is common in poultry semen due to artificial insemination.
- Antibiotics in semen extenders contribute to bacterial resistance.
- Alternative methods are needed to control bacterial contamination in poultry semen.
Purpose of the Study:
- To evaluate antimicrobial photodynamic therapy (PDT) as an antibiotic alternative for chicken semen.
- To assess the impact of methylene blue (MB) concentration, incubation time, light exposure, and irradiance on spermatozoa and bacteria.
Main Methods:
- Chicken semen samples were treated with varying concentrations and incubation times of methylene blue (MB).
- Samples were exposed to specific light doses and irradiances.
- Spermatozoa activity and bacterial colony counts were analyzed.
Main Results:
- MB and light alone did not negatively affect sperm parameters.
- Increased light dose during PDT significantly reduced sperm parameters.
- PDT conditions that preserved sperm viability failed to significantly reduce bacterial colonies.
Conclusions:
- Methylene blue (MB) lacks selectivity, hindering effective bacterial reduction in chicken semen via PDT.
- Further investigation into alternative photosensitizers or MB-conjugating molecules is required for successful PDT application in poultry.
