Pseudomonas japonica

To the Editor: Previous case series have suggested that approximately 5% of Pseudomonas bacteremias are due to nonaeruginosa Pseudomonas species. Typically, nonaeruginosa Pseudomonas species have higher rates of antimicrobial sensitivity, with one series reporting 32% resistance to ciprofloxacin and 7% to 10% resistance to ceftazidime.1 A 70-year-old man with type 2 diabetes and cirrhosis secondary to nonalcoholic steatohepatitis was admitted to the general internal medicine service for cellulitis at a large academic health sciences center in Toronto, Canada. Before admission, he had had 2 weeks of worsening ambulation and 1 day of progressive right leg pain and erythema. He also endorsed central abdominal pain over the same period without other bowel or urinary symptoms. He denied any recent travel or exposures besides being an avid gardener. On presentation, he was hemodynamically stable with bilateral leg pitting edema, profound erythema, and pain to the right leg and foot. There was also clear fluid-filled bullae in the right leg, without evidence of ulceration, apparent injury, or portal of entry (Fig. 1). Investigations demonstrated an abnormal urinalysis finding with a white blood count of 500, red blood cell count of 250, and nitrites. He had no leukocytosis, normal creatine kinase, normal electrolytes, normal liver enzymes, and an elevated lactate (2–5 mmol/L). Chest x-ray demonstrated evidence of volume overload, but no focal consolidation. Bilateral leg Dopplers demonstrated no thrombosis. Blood and urine cultures were sent, and the patient was treated empirically for cellulitis with intravenous cefazolin and for volume overload with diuretics. Although the patient remained hemodynamically stable, his cellulitis continued to worsen over the subsequent 7 days. Urine cultures grew Escherichia coli sensitive to cefazolin. Blood cultures grew gram-negative bacilli in 1 of 2 bottles. Microbiologic investigation of the gram-negative bacilli yielded a non–lactose fermenting, oxidase-positive organism, which was not Pseudomonas aeruginosa. While awaiting further investigation from the public health laboratory, therapy was broadened to piperacillin-tazobactam and ciprofloxacin for 3 days to provide dual coverage for potential resistant Pseudomonas species. The organism was eventually identified as Pseudomonas japonica, which was sensitive to all antipseudomonal antimicrobials. This organism was detected at the provincial public health laboratory using 16s rRNA gene sequencing. Therapy was stepped down to ciprofloxacin and cephalexin to complete 2 weeks of therapy, with subsequent complete resolution of the cellulitis.FIGURE 1: Our patient's affected (right) leg, with profound erythema, pitting edema, and clear, fluid-filled bullae.P. japonica is a novel Pseudomonas species first described in a 2008 microbiologic study by Pungrasmi et al.2 The strain was first isolated in 2000 from a municipal sewage treatment plant in Tokyo, Japan, hence the species name japonica.2 It is a gram-negative, aerobic, non–spore-forming rod that is non–lactose fermenting, and oxidase and catalase positive, and cannot reduce nitrate. By 16s rDNA analysis, this strain could not be placed in any known species of Pseudomonas. It shares 98% sequence homology with Pseudomonas putida. This organism is in the genus Pseudomonas sensu stricto, in the subcluster of P. putida group.3 Previous reports have demonstrated the pathogenic potential of P. putida, which has been associated with immunocompromise and chronic indwelling devices.4,5 We present the first documented case of infection due to P. japonica, successfully treated with ciprofloxacin. Further research is necessary to describe the spectrum, risk factors, and natural history of infections related to P. japonica. Eric Coomes, MDWilliam K. Silverstein, MD Department of Medicine University of Toronto Toronto, Ontario, Canada [email protected]Jonathan S. Zipursky, MD, FRCPC Department of Medicine and Division of Clinical Pharmacology and Toxicology University of Toronto Toronto, Ontario, CanadaKaveh Shojania, MD Department of Medicine University of Toronto Division of General Internal Medicine Sunnybrook Health Sciences Centre Toronto, Ontario, Canada

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