Detection of Legionella bozemanae, a New Cause of Septic Arthritis, by PCR Followed by Specific Culture

Abstract

Legionella bozemanae is a rare isolate in clinical specimens. We describe a case of joint infection due to L. bozemanae in an immunocompromised patient with dermatomyositis. Without the use of PCR screening or culture on specialized medium, the organism would not have been detected. CASE REPORTA 71-year-old woman with amyopathic dermatomyositis presented to the department of rheumatology with septic arthritis of the left knee. Her medical history included several admissions to the department during 2011, where she underwent a comprehensive diagnostic workup for dermatomyositis with underlying malignancy.During the investigation, three skin biopsy specimens were obtained, one close to the interphalangeal joint of her right thumb, one from the anterior aspect of the chest, and one from the right thigh. All of the skin lesions appeared as erythematous-toviolaceous papules and plaques.Unfortunately, the biopsy specimen from the thumb was complicated by septic arthritis due to Streptococcus agalactiae, followed by Staphylococcus aureus wound and bloodstream infections. However, the patient gradually recovered and the diagnostic program found no signs of malignancy. During the entire diagnostic workup, the patient had normocytic, normochromic anemia with hemoglobin levels of 5.0 to 7.0 mmol/liter.The patient was diagnosed with amyopathic dermatomyositis and started on immunosuppressive treatment with methotrexate (20 mg weekly), prednisolone (20 mg daily), and hydroxychloroquine (250 mg daily) and then discharged to a rehabilitation stay at a rheumatologic hospital. At discharge, both her white blood cell (WBC) count and her C-reactive protein (CRP) level were within normal the ranges.During this stay, the patient developed intermittent pain in her left thigh, with a concomitant rise in the CRP level to 24 mg/liter. During the next months, the pain in the thigh worsened and she experienced malaise and weight loss. Examination at our hospital revealed a swelling of her left knee. Ultrasound showed a large intracavital joint fluid effusion. Five milliliters of purulent aspirate was obtained from the left knee joint cavity (WBC count not available). Gram staining with carbol fuchsin as a counterstain showed numerous neutrophilic granulocytes but no bacteria or fungi. No crystals were detected. Cultures grown under standard conditions were negative (agar plates with 10% horse blood and thioglycolate broth [Statens Serum Institute, SSI Diagnostica, Hilleroed, Denmark] incubated for 48 h at 35°C with 5% CO 2 ). Blood samples showed anemia (5.4 mmol/liter), leukocytosis (WBC count of 13.9 ϫ 10 9 /liter with the following differential analysis: neutrophils, 12.4 ϫ 10 9 /liter; eosinophils, 0.0 ϫ 10 9 /liter; basophils, 0.0 ϫ 10 9 /liter; lymphocytes, 0.7 ϫ 10 9 /liter; monocytes, 0.8 ϫ 10 9 /liter), and an increased CRP level (54 mg/liter). X-rays of the left knee and chest were unremarkable. Blood and urine cultures were negative.Methotrexate treatment was withdrawn, and intravenous cefuroxime (1,500 mg three times daily) wa...

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Septic arthritis in immunocompetent and immunosuppressed hosts

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