ABSTRACT. Pyelonephritis, in which Staphylococcus intermedius was isolated, was diagnosed in a 4-year-old female Siberian tiger (Panthera tigris altaica). At necropsy, the renal pelvis was dilated with a large amount of purulent exudates. Microscopically, the lesions of renal pelvis and medulla consisted of necrotic foci intermingled primarily with numerous degenerative neutrophils and a few lymphocytes, plasma cells and macrophages. Bacteriology showed the presence of S. intermedius. This is the first report on pyelonephritis associated with S. intermedius in wild felidae. KEY WORDS: Panthera tigris altaica, pyelonephritis, Staphylococcus intermedius.J. Vet. Med. Sci. 69(8): 851-852, 2007 Staphylococcus intermedius is a gram-positive, nonmotile, non-spore forming, facultative anaerobic coccus [3], which is part of the normal microflora of the skin and mucosal surfaces of the upper respiratory tract of dogs, horses, cats, and minks [1,7]. This bacterium has also been isolated from the anterior nares of dogs and pigeons [4], and from infected dog bite wounds in humans [10]. S. intermedius may cause cutaneous, urinary tract, bone, and central nervous system infections in several animal species [1,7].In dogs, S. intermedius is one of the leading pus-forming bacteria and causes infections such as pyoderma and otitis externa [3,8]. Staphylococcus spp. does not generally appear to cause any major disease in cats [5], but cases of superficial dermatitis, bacterial folliculitis, and superficial pyoderma caused by S. intermedius have been reported [9]. About 10% (9/93) of Staphylococci obtained from feline clinical specimens were S. intermedius [3,5].Diseases associated with S. intermedius have not been reported in wild felidae. Here we describe an episode of a Siberian tiger (Panthera tigris altaica) kept at the Korea National Arboretum with pyelonephritis caused by S. intermedius.The four-year-old female Siberian tiger had been donated from China for breeding and was raised for four months alongside a male Siberian tiger at the Korea National Arboretum. After showing depression and anorexia over several days, the female tiger suddenly died. A postmortem examination was performed immediately.At necropsy, the dead Siberian tiger was thin and emaciated. No wounds or disease conditions were observed in the external body surfaces and orifices, and the tiger was not pregnant. Both kidneys were congested, and the pelvis of the left kidney was markedly dilated and filled with a large amount of inspissated purulent exudates (Fig. 1). No purulent exudates or any significant gross abnormalities were found in the urinary bladder and ureter. Representative samples from major parenchymal tissues, including the heart, lungs, liver, spleen, kidneys, small and large intestines, urinary bladder, ovaries and uterus, were fixed in 10% neutral phosphate-buffered formalin, routinely processed, embedded in paraffin, and stained with hematoxylin and eosin (HE) for histopathologic examinations. The normal histologic architecture of the rena...