Bacterial pathogens are a potential cause when a mare fails to conceive to a fertile stallion on a well-managed breeding farm on one or more cycles in the same season. Furthermore, emerging bacterial resistance to commonly used (topical) antibiotics has been demonstrated. In this study, a total of 586 uterine swabs from mares with fertility problems were evaluated and the bacterial isolates were identified and measured for resistance to 10 antibiotics most commonly used during bacterial equine infection. Forty-nine percent of the examined mares were positive at bacteriological investigations. Amongst 347 successful isolations, 31.7% were Streptococcus group C and 18.4% Escherichia (E.) coli, both considered frequently associated with fertility problems. Determination of the antibiotic susceptibility pattern of Streptococcus group C (110 organisms) revealed that only the amoxicillin/clavulanic acid was highly active with 82.7% of the isolates being inhibited. For E. coli, a major number of drugs displayed a high potency.