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Comparisons of antibiotic combinations to control Pseudomonas aeruginosa in bovine semen
1Department of Pathobiology, Animal Diseases Research Institute, Nepean, Ontario.
Abstract:
Raw semen experimentally contaminated with 10(6) Pseudomonas aeruginosa cells per milliliter was processed for use in artificial insemination (AI) using three different antibiotic combinations: a) gentamicin, lincomycin, spectinomycin and tylosin (GLST) directly added to contaminated raw semen followed by dilution with whole milk or egg yolk Tris containing GLST; b) penicillin, streptomycin, lincomycin, spectinomycin and minocycline (PSLSM) in whole milk used to dilute the contaminated raw semen followed by further dilution with glycerolated milk containing PSLSM; and c) penicillin, streptomycin, lincomycin and spectinomycin (PSLS) used with egg yolk Tris diluent in the same way as PSLSM and milk. Diluted semen was incubated at 35 degrees C for 5 or 40 min before cooling commenced. To assess the efficacy of the antibiotics in controlling P. aeruginosa, diluted semen samples were cultured for the organism before and after freezing. The GLST antibiotics added to raw semen and milk reduced the counts of P. aeruginosa before or after freezing. When egg yolk Tris was used, GLST inhibited the organism as indicated by its low growth in culture before freezing and absence of growth from samples after freezing. With PSLSM and PSLS treatments, the organism was recovered in milk and egg yolk Tris processed semen both before and after freezing. However, incubation at 35 degrees C for 40 min prior to cooling, compared to incubation of 5 min, appeared to reduce the bacterial counts after freezing.
Insights
Gentamicin, lincomycin, spectinomycin, and tylosin (GLST) effectively controlled Pseudomonas aeruginosa in semen for artificial insemination (AI). Egg yolk Tris diluent enhanced GLST efficacy, preventing bacterial growth post-freezing.
Area of Science:
- Veterinary Microbiology
- Animal Reproduction
Background:
- Pseudomonas aeruginosa contamination poses a significant threat to semen quality for artificial insemination (AI).
- Effective antibiotic strategies are crucial for maintaining bacterial control in processed semen.
Purpose of the Study:
- To evaluate the efficacy of three different antibiotic combinations in controlling Pseudomonas aeruginosa contamination in raw semen intended for AI.
- To assess the impact of semen processing methods and incubation times on antibiotic effectiveness.
Main Methods:
- Raw semen was experimentally contaminated with P. aeruginosa and treated with antibiotic combinations: GLST, PSLSM, and PSLS.
- Semen was diluted using whole milk or egg yolk Tris extenders, with or without antibiotics.
- Samples were incubated at 35°C for 5 or 40 minutes before cooling and freezing.
- Bacterial counts were assessed via culture before and after cryopreservation.
Main Results:
- The GLST antibiotic combination significantly reduced P. aeruginosa counts in both milk and egg yolk Tris extenders, especially when used with egg yolk Tris.
- PSLSM and PSLS treatments showed limited efficacy, with P. aeruginosa consistently recovered before and after freezing.
- A longer incubation period (40 min vs. 5 min) at 35°C appeared to reduce bacterial counts post-freezing.
Conclusions:
- GLST is a promising antibiotic combination for controlling P. aeruginosa in semen for AI, particularly when combined with egg yolk Tris extender.
- The choice of extender and processing conditions significantly influences antibiotic efficacy against bacterial contamination in semen.