Co-Infection of Chickens with and from an Outbreak of Arthritis, Synovitis, and Osteomyelitis Argues for Detailed Characterisation of Isolates

species are widespread in poultry environments and can cause various infections, often when the host's defences are compromised. This manuscript reports on a co-infection of chickens with and associated with an outbreak of arthritis, synovitis, and osteomyelitis in an organic broiler breeder flock in Austria. Clinically, the affected flock showed weakness, lethargy, lameness, and increased mortality. Post-mortem examinations identified purulent arthritis and femoral head necrosis. Bacteriological analysis using MALDI-TOF MS identified both and in the affected joints. Antibiotic resistance testing revealed significant resistance, particularly in . Histological analysis showed severe inflammation and bacterial colonies in the joints. While is a common pathogen in poultry, is less frequently reported. This study emphasises the need for detailed bacterial characterisation in outbreaks to better understand the role of less common pathogens like . Further research is necessary to elucidate the impact of on poultry health and its role in causing arthritis and synovitis, highlighting the importance of comprehensive investigation in such outbreaks.