Cooled Storage of Canine Semen:in vitroEffects of Different Concentrations of an Antibiotic Combination on Growth of Mollicutes

Comparing different sperm concentrations for optimizing cooled semen use in the dog

The use of shipping canine semen for artificial insemination has bloomed over the last 20 years. This allows for the spread of genetic material while overcoming geographical or time-related challenges. The optimal sperm concentration for cooled semen transport in the dog is unknown. Often canine semen is extended 1:3-5 vol:vol without standardized sperm concentrations for cooled shipment. We compared different sperm concentrations for cooled storage and hypothesized that lower concentrations would result in better semen quality. Semen was collected from healthy client-owned dogs (n = 8). Individual ejaculates were divided into a control aliquot (CON) extended 1:3 vol:vol with a commercial extender. The remaining sample was centrifuged and extended to 200 ×106 sperm/ml (C200), then serially diluted to 100, 50, and 25 ×106 sperm/ml concentrations (C100-C25). Aliquots were cooled for 24 h and then centrifuged and re-extended. Sperm concentration, plasma membrane integrity (PMI, %), motility (subjective total, STM; computer-assisted sperm analysis (CASA) total and progressive, TM, PM; %), and normal morphology (NM, %) were assessed in raw semen (T0), post-extension (T1), after 24 h of cooling (T2), and after processing at 24 h (T3). Cooling resulted in significant declines in STM and NM for all groups and in decreased PMI for CON and C25-50. After cooling (at T2), PMI was significantly lower for C25 compared with all the groups and higher for CON compared with C25-100 (p ≤ 0.038). Processing and re-extension after cooling further decreased the spermiogram parameters. At T3, PMI for CON was similar to C200 but significantly higher than C25-100, while C25 had the lowest PMI. For motility parameters and NM, C25 performed worse than all or most of the other groups. Comparing CON at T3 with C25-200 at T2, PMI, STM, and NM for CON were significantly lower than C25-200, C200, and C100-200, respectively. In conclusion, our results show that cooling canine semen for 24 h at 200 ×106 sperm/ml final concentration after processing or extending 1:3 vol:vol without centrifugation is preferred based on the highest PMI. If volume restrictions apply, processing raw semen and extending to the desired volume with higher sperm concentrations at the collection facility is superior to centrifugation and volume adjustment after 24 h of cooled storage.

Double semen collection at a 1-h interval in dogs decreases the bacterial contamination of canine ejaculates

Semen extenders usually contain antibiotics with the aim to minimize bacterial growth, but the indiscriminate use of antibiotics increases the emergence of multidrug-resistant bacteria. A limiting factor of semen processing in dogs is the low total sperm count that limits the number of insemination doses that can be obtained from one ejaculate. Therefore, two ejaculates collected at a short interval can be combined to increase the number of AI doses. In this study, semen was collected from dogs either once or the same dogs (n = 28) were submitted to dual semen collection 1 h apart. All ejaculates were submitted to bacteriological analysis. We hypothesized that bacterial contamination of semen is low but that a dual semen collection might increase contamination. A sample for bacteriological examination was taken from raw semen immediately after semen collection. Bacteria including mycoplasmas were isolated using conventional cultivation procedures and isolates were identified to the species level by matrix-assisted laser desorption ionization - time of flight (MALDI-ToF) mass spectrometry. In total, 22 bacterial species were identified in the 84 ejaculates with Mycoplasma cynos, Streptococcus canis and Canicola haemoglobinophilus being most frequent. Bacterial growth was sporadic in 16 and absent in 10 ejaculates. The overall bacterial growth was lower in the second than in the first ejaculate of dual semen collections (p < 0.05). The percentage of motile and membrane-intact spermatozoa in frozen-thawed ejaculates was not associated with the degree of bacterial contamination of raw semen. In conclusion, there was only limited microbial contamination in dog semen and the microorganisms isolated are considered part of the normal genital bacterial flora. Repeated semen collection reduced bacterial contamination in the second in comparison to the first ejaculate. The use of antibiotics in canine semen should be questioned.

Antibiogram of Microorganisms Isolated from Fresh and Frozen Semen of Crossbred Frieswal Bulls

BACKGROUND: The bacterial contaminants in the semen are a major concern for most of the semen production laboratories because they adversely affect the semen quality. During sperm cryopreservation, the inclusion of antimicrobials in extenders may help to minimize bacterial growth. However, due to bacterial resistance to commonly used antimicrobials, they cannot fully assure microbiological safety to the frozen semen. OBJECTIVE: To estimate the microbial load and antibiogram of microorganisms isolated from the fresh and frozen bull semen. MATERIALS AND METHODS: The bacterial load was estimated in fresh and frozen semen samples of crossbred Frieswal bulls by the pour plate method. Microorganisms were identified as Gram positive and Gram negative by Gram staining. The representative bacterial colonies were streaked onto different specific media which were further confirmed by biochemical tests. Bacterial isolates were subjected to in vitro antibiotic sensitivity test. RESULTS: The average microbial load of fresh and frozen semen samples was found to be 8397.4±524.31 cfu/mL and 680.87±105.41cfu/mL, respectively. Microorganisms belonging to Staphylococcus aureus, Staphylococcus epidermidis, Proteus, Klebsiella, Bacillus cereus, Bacillus subtilis, Actinomyces, E. coli, Rhodococcus, Neisseria and Micrococcus were identified in the semen samples. The antibiotic sensitivity testing of the bacterial isolates revealed that benzyl penicillin was found to be the least effective against the isolated organisms while gentamicin and spectinomycin were found to be most effective among the antibiotics used. Lincomycin, tylosin and streptomycin showed moderate efficacy against the bacterial isolates. CONCLUSION: Gentamicin, tylosin, lincomycin, and spectinomycin (GTLS) antibiotic combination is more effective against bacterial isolates and may be added to semen extender to better control bacterial load and semen quality. .

Current and alternative trends in antibacterial agents used in mammalian semen technology

The use of antibacterial substances as additives in extenders for ensuring the sanitary quality of the semen employed in reproductive biotechniques and preserving it from bacterial deterioration has been reported since the mid-twentieth century. However, the deleterious effects of these drugs on the sperm quality as well as their effectiveness in controlling bacterial growth in the preserved semen have been questioned. The aim of this review was to report the antimicrobials primarily used in the extenders added to the semen of mammals, and to present alternatives to their use. Among the various mammalian species, there is a large variation regarding the antimicrobial types added to semen extenders as cephalosporins (ceftiofur, cefdinir, eg) and quinolones (ofloxacin, ciprofloxacin), alone or in combination with large action spectra substances as penicillin-streptomycin and gentamicin-tylosin-lincomycin-spectinomycin. To combat problems related to bacterial resistance to these drugs, the emergence of alternatives is increasingly evident. Among these alternatives, use of physical methods as centrifugation and filtration, as well as the use of antimicrobial peptides and other substances from different origins have been highlighted for presenting antimicrobial potential.

Antibiotic resistance in microorganisms isolated in a bull semen stud

Many microorganisms from various sources may be present in ejaculates of bulls. This study identified and isolated bacteria from bull sperm samples in a commercial stud and evaluated their resistance to antibiotics. The number of colony-forming units was determined in semen samples collected at distinct steps during freezing and thawing. The minimum inhibitory concentration and the minimum bactericidal concentration were determined for four antibiotics commonly used in commercial studs. A total of 135 microorganisms from 25 genera were isolated. After a sensitivity test, all evaluated microorganisms (n = 55) were resistant to penicillin and most of them were resistant to tylosin and lincomycin (n = 54). Resistance to all tested antibiotics was observed in 22% of all isolates, whereas only 3.9% of the isolates were inhibited by the tested antibiotics at the concentrations recommended by the international legislation. As the isolated microorganisms presented high resistance to frequently used antibiotics, sensitivity tests should be periodically conducted in commercial bull semen studs to prevent the use of contaminated semen in artificial insemination.

Survival capacity of Mycoplasma agalactiae and Mycoplasma mycoides subsp capri in the diluted semen of goat bucks and their effects on sperm quality

This study examines the viability of Mycoplasma agalactiae (Ma) and Mycoplasma mycoides subsp capri (Mmc) during 150 minutes of incubation at 37 °C in contaminated diluted semen (DS) doses. The effects of the presence of both microorganisms on sperm viability, motility, and morphology were also examined. In a second experiment, the viability of Ma and its effects on sperm viability were determined in ejaculate samples and skimmed milk semen extender samples. Ma and Mmc were able to survive in DS at concentrations considered infectious, and no significant differences in mean concentrations were detected (7.1 log colony-forming units [CFU]/mL). However, initial concentration of Ma declined (P < 0.05) from 7.5 to 6.9 log CFU/mL and Mmc declined (P < 0.05) from 7.7 to 7.1 log CFU/mL after incubation. Conversely, ejaculate concentrations of Ma increased significantly (from 7.1 to 7.4 log CFU/mL, P < 0.05). These observations suggest that the natural breeding medium is more suitable for Ma than the medium used for artificial insemination (AI). The presence of Mmc slightly reduced sperm viability in the DS (from 21.7% to 16.6%, P < 0.05). The absence of major effects on sperm quality could lead to the unnoticed use of semen contaminated with Ma and Mmc for AI. As both bacteria were able to survive the conditions of ejaculates and semen doses, these findings suggest a risk of venereal transmission of contagious agalactia and support the use of mycoplasma-free semen samples for (AI).

The effects of antibiotic additions to extenders on fresh and frozen-thawed bull semen

Reproduction in dairy cows is based around the use of cryopreserved semen. Antibiotics are utilized to control bacterial contamination and growth in cryopreserved bull semen. The antibiotic resistance of some bacteria required the evaluation of new antibiotic combinations with a high level of antibacterial effectiveness and a negligible effect on spermatozoa. In this research, we studied the effect of the fluorinate carboxyquinolone ofloxacin and the combination of ceftiofur/tylosin on bull spermatozoa and in-field bacterial growth. In Experiment 1, the toxicity of different levels of ofloxacin and ceftiofur/tylosin was tested by the incubation of bull spermatozoa and the evaluation of sperm kinetic parameters, membranes and acrosome integrity after dilution, and at 60 and 120 min after incubation. The data reported in this study reveals that both antibiotic combinations, at all concentrations, seem to have a negligible effect on spermatozoa with respect to all of the parameters examined (p>0.05). Furthermore, progressive motility was significantly higher for sperm diluted with both antibiotic combinations compared with samples without antibiotics (p<0.01). In Experiment 2, the ability of ofloxacin or ceftiofur/tylosin to control bacterial growth during bovine semen cryopreservation was compared with the combination of gentamicin/tylosin/spectinomycin/lincomycin. A significant reduction in progressive motility was found in cooled semen with respect to all of the antibiotic treatments (p<0.05). However, the membrane integrity was found to significantly rise in frozen samples with, compared to samples without, antibiotics (p<0.05). In a bull, gentamicin, tylosin, spectinomycin, and lincomycin failed to control bacterial growth in the cryopreserved sample, while no such growth was found in samples extended with ceftiofur/tylosin or ofloxacin. In conclusion, both ceftiofur/tylosin and ofloxacin can be safely added to bull seminal extenders, and both can protect insemination doses from bacteria that are resistant to other antibiotic combinations.