The influence of antimicrobial agents on the development of antibiotic resistance in the vaginal bacterial flora of artificially inseminated mares : a study on mares in a stud environment
In Sweden and in many other countries, artificial insemination (AI) is frequently used in horse breeding. The technology makes it possible to use genetic material from horses in different geographical locations in an effective way, minimizing the risk of infection or even injury to both horses an...
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| Formato: | H3 |
| Lenguaje: | Inglés sueco |
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SLU/Dept. of Clinical Sciences (until 231231)
2021
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| Sumario: | In Sweden and in many other countries, artificial insemination (AI) is frequently used in horse
breeding. The technology makes it possible to use genetic material from horses in different
geographical locations in an effective way, minimizing the risk of infection or even injury to both
horses and stud personnel. Semen collection is performed with a high hygienic standard but despite
this, it is seldom possible to obtain an ejaculate that does not contain bacteria. Bacteria in the
ejaculate can cause disease in the mare, or result in a deterioration in sperm quality, thereby reducing
the chance of the mare becoming pregnant after insemination. To ensure disease control and
maintain sperm quality, addition of antibiotics to the semen is therefore required to reduce the
number of bacteria in the ejaculate. To protect the spermatozoa during storage, a semen extender
containing both buffering and nutrient-rich components, but also antimicrobial substances (AMS)
is added. During insemination, the semen dose is deposited in the mare's uterus, which initiates a
response from the local immune system. This results in an immunological and mechanical cleansing
of the deposited material through the cervix uteri, which is an important function for maintaining a
healthy uterine environment and enabling a pregnancy. The mare's vaginal bacterial flora is therefore
exposed to the antibiotics contained in the extender, which could theoretically increase the risk of
developing antibiotic resistance in the bacterial flora.
In this study, vaginal swabs were obtained from 39 mares of varying breeds and ages in northern
Sweden, with the aim of investigating the normal vaginal bacterial flora and how its resistance
pattern is affected by the exposure to the antibiotics (penicillin and gentamicin) contained in the
semen extender INRA-96, and if resistant bacteria are present in the normal vaginal flora of mares.
The mares were categorized into either an exposed group consisting of breeding mares at a stud
farm, or a control group consisting of mares that had never been inseminated. Swabs were taken
from a predetermined area in the cranial vagina just before the first insemination of the season (D0),
with a follow-up sample after three days (D3). The control group was sampled only once, as far as
possible in connection with estrus. The samples were sent by post to the Department of Biomedical
Science and Veterinary Public Health, SLU, Uppsala for analyses. Isolated bacteria were identified
by Matrix-Assisted Laser Desorption / Ionization Time of Flight Mass Spectrometry (MALDI-TOF
MS). Bacterial species that could be isolated from both D0 and D3 in the same mare were analysed
regarding antimicrobial resistance. A comparison was also made between the bacteria and resistance
pattern of bacteria from mares that had never been inseminated. A total of 971 bacterial isolates
were isolated from the 39 mares, with E. coli being by far the most common isolated bacterium
(48.6%). The bacteria included in the antimicrobial susceptibility testing were Staphylococcus
simulans, Streptococcus equi ssp. zooepidemicus, Streptococcus dysgalactiae and Enterococcus
faecalis. Resistant isolates were identified in all species except Enterococcus faecalis. These isolates
showed resistance to penicillin, oxacillin, fusidic acid, trimethoprim, erythromycin, clindamycin,
nitrofurantoin and tetracycline, depending on species.
Exposure to antibiotics did not affect the resistance pattern in the vaginal bacterial flora in this
study, but there was a difference in the bacterial species obtained before and after insemination
and between the exposed group and the control group. Resistant bacteria were found in the vaginal
flora of both groups. |
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