Table 2.

Main infectious etiologies for refractory monoarthritis: What do you find?

Microorganism	Medium	Stains	Histology
Mycobacterium tuberculosis (40)	Agar-based and egg-based media incorporating green malachite and Middlebrook broths or solid media	Ziehl-Neelsen	Caseating or non-caseating granulomas
Fungi (41)	Sabouraud's dextrose agar	Gomori methenamine silver, periodic acid Schiff	Candidiasis: thickened synovial membrane with non-specific mononuclear infiltration. Sporotricosis: mixed granulomatous and pyogenic processes. Rarely, asteroid bodies consisting of a central basophilic yeast surrounded by eosinophilic material radiating outward. Coccidioidosis: villonodular synovitis or typical pannus formation with non-caseating granulomas and sphreules containing coccidioidal endospores. Criptococcosis: both acute and chronic synovitis.
Mycobacterium leprae (42)	Almost impossible to culture in a laboratory; PCR techniques for detecting DNA exist, but are currently not used in clinical practice.	Fite-Faraco staining	Non-specific granulomatous synovitis, epithelioid cells