Abstract
Background:
Mastitis in horses is an uncommon but clinically significant condition, typically associated with milk accumulation and opportunistic bacterial pathogens. This report details unusual case of multiple bacterial mastitis involving Streptococcus dysgalactiae subsp. equisimilis and multidrug-resistant Trueperella pyogenes.

Case description:
A 5-year-old English mare was presented for swelling and hardening of one side of the udder with pus discharge. The mare developed chronic scarring in the left side of the udder, while the right side showed signs of sudden inflammation. Bacteriological Laboratory tests from milk samples from the affected left side identified Streptococcus dysgalactiae subsp. equisimilis (SDSE) and a multidrug-resistant strain of Trueperella pyogenes. Blood sample analysis revealed ongoing inflammation with high neutrophil levels, anemia, and elevated fibrinogen. The treatment plan involved marbofloxacin (5 mg/kg IM daily for five days), flunixin meglumine (2.5 mg/kg IM daily for five days), and regular local wound care using hydrogen peroxide washes and povidone-iodine packs. The mare fully recovered within 12 days, and no further issues were reported.

Conclusion:
This case demonstrates the zoonotic risk of Trueperella pyogenes and SDSE, effective targeted antimicrobial treatment, and the value of advanced diagnostics for equine mastitis in low-resource areas.

Key words: Equine mastitis; Trueperella pyogenes; Streptococcus dysgalactiae subsp. equisimilis (SDSE); Libya.