ANTIBIOTICS FOR THE PRESERVATION OF KOALA (PHASCOLARCTOS-CINEREUS) SEMEN

Aim To determine the normal microbial flora of the koala ejaculate and prepuce in order to select appropriate antibiotics for addition into diluents designed for the preservation of semen. Procedure Bacteriolog ical samples of the koala prepuce (n = 12) and ejaculate (n = 20) were submitted for microbial culture and sensitivity testing. Microbial fl ora of ejaculates collected by electroejaculation and artificial vagin a were compared. The effects of varying concentrations of penicillin G and gentamicin on sperm motility and on the growth of bacteria in dil uted semen stored at room temperature and 16 degrees C over a 24 h per iod were investigated. Results A range of bacteria was isolated from t he koala prepuce and ejaculate. The predominant organisms in semen col lected by electroejaculation and artificial vagina were Corynebacteriu m spp, none of which could be assigned to any recognised species. The addition of penicillin G and gentamicin to a PBS-based diluent at dose rates of 1000 to 2000 IU/mL and 100 to 200 mu g/mL respectively, resu lted in no adverse effect on sperm motility over a 24 h incubation per iod. Penicillin G (1000 IU/mL) and gentamicin (100 mu g/mL) prevented growth of bacterial contaminants in diluted koala semen. Conclusion By controlling the growth of bacteria in extended koala semen, penicilli n G and gentamicin are likely to lengthen the period by which spermato zoa can be stored at 16 degrees C and reduce the possibility of diseas e transmission during artificial insemination procedures.