Development of antimicrobial resistance in Staphylococcus lugdunensis during treatment-report of a case of bacterial arthritis, vertebral osteomyelitis and infective endocarditis.

Staphylococcus lugdunensis is a recently described coagulasenegative staphylococcus (CNS) that has been associated with a wide range of human infections [1,2]. The most frequent type of infection reported is infective endocarditis which may involve prosthetic as well as native valves [3]. In this paper we present a patient with bacterial arthritis in both knee joints (one with and one without an arthroplasty), vertebral osteomyelitis and infective endocarditis of nativemitral and aortic valves. The patient was a 79-year-old male, non-smoking, former lumberjack with a history of psoriasis and hypertension. He had seropositive rheumatoid arthritis with general joint aiection. His rheumatoid arthritis was treated with corticosteroids, methotrexate and non-steroidal anti-in£ammatory drugs. He underwent total replacement of the left knee in November 1992 because of severe osteoarthritis. The right knee did not show any signs of osteoarthritis until the end of 1994. He was admitted in April 1995 due to cellulitis of the right elbow and an infected ulcer on the left foot. Blood cultures showed growth of CNS, later veri¢ed to be S. lugdunensis. After initial intravenous treatment with benzylpenicillin and dicloxacillin for 2 days, the patient was treated with oral clindamycin for 2 weeks and the clinical course was uneventful. On follow-up at the beginning of May, the patient was well and the C-reactive protein (CRP) serum concentration was 21mg/L. Nine days later he was readmitted due to bacterial arthritis of the right knee. Cultures were positive for CNS (later shown to be S. lugdunensis) in both blood and synovial £uid. This time, treatment comprised intravenous cloxacillin for 6 days, then oral £ucloxacillin 1g three times a day for 6weeks, and then £ucloxacillin 0.5 g three times a day for 7months, in accordancewith the susceptibility test. A systolic heart murmur, not previously recognized, led to a transthoracic echocardiography (TTE) being performed in August 1995. The TTE showed mild-to-moderate aortic and mitral valve regurgitation. No vegetations were seen. The patient was followed with repeated determinations of CRP and ESRvalues (CRP 10^20mg/L and ESR 20^30mm/1h) for several months, pending total replacement of the right knee because of osteonecrosis.This was performed in November 1995. Antibiotic prophylaxis was given as intravenous cloxacillin 2 g three times a day for 7 days, and the patient was discharged with oral £ucloxacillin 0.5 g three times a day, whichwas continued until January1996. In June 1996 the patient was admitted once more but now presented symptoms of swelling, pain, eiusion and warmth of the left prosthetic knee. Arthrocenthesis was performed and the patient was given oral £ucloxacillin. The symptoms recurred over the following year.The CRP levels were 40^80 mg/L and the ESRwas 50^100mm/1h when the symptoms were present. X-ray investigation of the left knee from this period showed signs of osteitis. Altogether, six cultures of synovial £uid were taken from the left knee during this period, and they all showed growth of CNS, which in February 1997 was typed as S. lugdunensis. Initially, the patient was treated with oral £ucloxacillin, but repeated susceptibility tests showed that the isolate had developed resistance to £ucloxacillin in December1996 and the treatment was changed to cipro£oxacin (Table1). Later, the isolated strain also showed a signi¢cantly increasedMIC for cipro£oxacin, and the antibiotic treatment was changed to clindamycin. In June 1997 the patient presented with a history of lower back pain and arthralgia of the hips, and at this time the CRP was 175mg/L. The antibiotic regimen was changed to oral rifampicin plus cipro£oxacin.The patient improved, the CRP level decreased, and the patient remained well until the end of August 1997, when he was readmitted due to fever, back and hip pains. A magnetic resonance imaging (MRI) scan showed signs of vertebral osteomyelitis, andTTE showed calci¢cation of the aortic and the mitral valves but no signs of endocarditic vegetations. Mild-to-moderate mitral and aortic valve regurgitation was present, but no signs of cardiac decompensation. Blood cultures showed growth of S. lugdunensis, and the strain had now developed resistance to rifampicin. Corticosteroids CONCISE COMMUNICATIONS