Moelerella wisconsensis: first isolation from lungs and spleen of a horse infected with Streptococcus dysgalactia subsp. equisimilis.

Moellerella wisconsensis is a Gram-negative, facultative anaerobic bacillus of Entero-bacteriaceae family, and it is an uncommon pathogen in domestic animals. To date, five cases were reported including two dogs, two cattle, and a goat. Streptococcus equisimilis is the second common bacterial agent after the S. equi subsp. zooepidemicus in equine pneumonia cases. The present report describes the isolation of M. wisconses from lungs and spleen of a 10-year-old Arabian horse (May 08, 2022) at post-mortem examination being co-infected with S. equisimilis. Clinical and pathological findings included bilateral nasal discharge, conjunctivitis, sternal recumbency, severe diffuse necrosuppurative rhinitis, multi-focal fibrinopurulent pneumonia and purulent lymphadenitis. Polymerase chain reaction assays showed no viral nucleic acids of equid alphaherpesvirus (EHV) 1, EHV-4, equine arteritis virus and equine papilloma virus. The antibiogram test revealed that the isolate was sensitive to several antibiotics except colistin. Taken together, the present report documents the first isolation of M. wisconsensis from lungs and spleen of a horse; hence, experimental studies are needed to clarify the pathogenity and pathogenesis of M. wisconsensis.