which is responsible for the above condition

Fish Tank Granuloma * Caused by atypical mycobacterial infection * Recreational or occupational exposure to contaminated freshwater or saltwater * Affects elbows, knees, feet, knuckles or fingers * Often single lump which causes crusty sore or abscess * Other lumps on course of lymphatic drainage * More widespread if immuno-compromised * Treated with long course of minocycline or co-trimoxazole 6-12 weeks ref : ananthanaryana 9th ed