Staphylococcus lugdunensis vertebral osteomyelitis
2003; Elsevier BV; Volume: 9; Issue: 11 Linguagem: Inglês
10.1046/j.1469-0691.2003.00777.x
ISSN1469-0691
Autores Tópico(s)Bacterial Identification and Susceptibility Testing
ResumoWe report a case of vertebral osteomyelitis due to the coagulase-negative staphylococcus, Staphylococcus lugdunensis. This is only the second such case reported in the literature in an immunocompetent host. When the patient's lumbar spine inflammatory mass was drained, the coagulase-negative staphylococcus obtained was discarded as a likely contaminant. We discuss the situation when coagulase-negative staphylococci require further identification and look at the unique features of S. lugdunensis. Isolation of S. lugdunensis is usually significant, and the organism should not be discarded as a contaminant without careful consideration. We report a case of vertebral osteomyelitis due to the coagulase-negative staphylococcus, Staphylococcus lugdunensis. This is only the second such case reported in the literature in an immunocompetent host. When the patient's lumbar spine inflammatory mass was drained, the coagulase-negative staphylococcus obtained was discarded as a likely contaminant. We discuss the situation when coagulase-negative staphylococci require further identification and look at the unique features of S. lugdunensis. Isolation of S. lugdunensis is usually significant, and the organism should not be discarded as a contaminant without careful consideration. Staphylococcus lugdunensis is a coagulase-negative staphylococcus which has only relatively recently been described [1Freney J Brun Y Bès M et al.Staphylococcus lugdunensis sp. Nov. and Staphylococcus schleiferi sp. Nov., two species from human clinical specimens.Int J Syst Bacteriol. 1988; 38: 168-172Crossref Scopus (287) Google Scholar]. It has been associated with a wide variety of infections, particularly of the skin and soft tissues, and endocarditis. However, unlike other coagulase-negative staphylococci (CNS), it seems to have a pathogenic potential similar to that of Staphylococcus aureus. Although CNS in clinical specimens are often discounted as contaminants, S. lugdunensis is rarely a contaminant [2Herchline TE Ayers LW Occurrence of Staphylococcus lugdunensis in consecutive clinical cultures and relationship of isolation to infection.J Clin Microbiol. 1991; 29: 419-421PubMed Google Scholar], and its isolation should be considered significant unless there is convincing evidence to the contrary. S. lugdunensis has only rarely been reported in association with bone and joint infections, and then either in association with prosthetic joints, following surgery or in immunocompromised patients. We report a case of vertebral osteomyelitis due to S. lugdunensis in an immunocompetent patient, without a preceding operative history. This is only the second such case reported in the literature of which we are aware. An 81-year-old caucasian man, with a previous history of ischemic heart disease, was admitted with a 5-week history of back pain. The pain had started acutely after he had lifted a bag of sand. One week prior to admission, he had complained of weakness in his legs and collapsed on two occasions. Physical examination on admission revealed a low-grade fever and tenderness over the mid-lumbar vertebrae. Power in his lower limbs was normal, but knee reflexes were absent and he had a negative Babinski response. His white cell count was 12.6 × 109/L, his hemoglobin level was 130 g/L, and his platelet count was 329 × 109/L. The C-reactive protein (CRP) was elevated at 137 mg/L, and the erythrocyte sedimentation rate (ESR) was 90 mm/h. A plain film of his lumbar spine revealed partial collapse of the vertebral bodies of L3 and L4. A magnetic resonance imaging (MRI) scan confirmed discitis of the intervertebral disk at L3/4, with involvement of the adjacent vertebrae and collapse of L4 (Figure 1). A transthoracic echocardiogram showed no evidence of endocarditis. Gram-positive cocci, which were coagulase negative (Staph Latex Kit, Pro-lab diagnostics, Ontario, Canada), were isolated from three sets of blood cultures. All strains were identified as S. lugdunensis, using API Staph (bioMerieux, Marcy L'Etoile, France). The organism was fully sensitive to penicillin, flucloxacillin, erythromycin, gentamicin and rifampicin, but resistant to trimethoprim. The patient was started on treatment with intravenous flucloxacillin and gentamicin, and transferred to a neurosugical unit at a different hospital, for biopsy and drainage of a lumbar spine inflammatory mass. A coagulase-negative staphylococcus was cultured from the pus obtained, but this was discarded as a likely contaminant, without further identification. Deteriorating renal function, deranged liver function and nosocomial pneumonia complicated the patient's clinical course. Because of these complications, the antibiotics were changed after 2 weeks to flucloxacillin and fucidic acid, then after a further 2 weeks to intravenous ampicillin. On this antibiotic, the patient's renal and liver function settled, and it was continued for 2 months, before being changed to oral amoxicillin, 1 g, three times daily. The patient made a steady recovery, his back pain settled, and his mobility improved. A follow-up MRI scan after 4 weeks of treatment showed no deterioration in the appearances of the lumbar spine. After a prolonged inpatient stay, the patient was discharged. At the time of discharge, the CRP had returned to normal but the ESR remained elevated at 89 mm/h. The ESR eventually returned to normal 9 months after the initial admission. The patient completed a total of 6 months of antibiotic therapy and remains well after 1 year of follow-up. S. lugdunensis was first described in 1988 by Freney et al. [1Freney J Brun Y Bès M et al.Staphylococcus lugdunensis sp. Nov. and Staphylococcus schleiferi sp. Nov., two species from human clinical specimens.Int J Syst Bacteriol. 1988; 38: 168-172Crossref Scopus (287) Google Scholar], and has been isolated from a variety of sources, but most frequently from skin and soft tissue [2Herchline TE Ayers LW Occurrence of Staphylococcus lugdunensis in consecutive clinical cultures and relationship of isolation to infection.J Clin Microbiol. 1991; 29: 419-421PubMed Google Scholar]. S. lugdunensis has also been associated with bacteremia [3Fleurette J Bes M Brun Y et al.Clinical isolates of Staphylococcus lugdunensis and S. schleiferi: bacteriological characteristics and susceptibility to antimicrobial agents.Res Microbiol. 1989; 140: 107-118Crossref PubMed Scopus (124) Google Scholar], brain abscess [3Fleurette J Bes M Brun Y et al.Clinical isolates of Staphylococcus lugdunensis and S. schleiferi: bacteriological characteristics and susceptibility to antimicrobial agents.Res Microbiol. 1989; 140: 107-118Crossref PubMed Scopus (124) Google Scholar], peritonitis [3Fleurette J Bes M Brun Y et al.Clinical isolates of Staphylococcus lugdunensis and S. schleiferi: bacteriological characteristics and susceptibility to antimicrobial agents.Res Microbiol. 1989; 140: 107-118Crossref PubMed Scopus (124) Google Scholar], vascular prosthesis infection [3Fleurette J Bes M Brun Y et al.Clinical isolates of Staphylococcus lugdunensis and S. schleiferi: bacteriological characteristics and susceptibility to antimicrobial agents.Res Microbiol. 1989; 140: 107-118Crossref PubMed Scopus (124) Google Scholar] and endocarditis [4Vandenesch F Etienne J Reverdy ME Eykyn SJ Endocarditis due to Staphylococcus lugdunensis: report of 11 cases and review.Clin Infect Dis. 1993; 17: 871-876Crossref PubMed Scopus (165) Google Scholar]. It has only rarely been reported in association with bone and joint infections, and then either in immunocompromised patients [5Murdoch DR Everts RJ Chambers ST Cowan IA Vertebral osteomyelitis due to Staphylococcus lugdunensis.J Clin Microbiol. 1996; 34: 993-994PubMed Google Scholar], following arthroscopy [6Palazzo E Pierre J Besbes N Staphylococcus lugdunensis arthritis: a complication of arthroscopy.J Rheumatol. 1992; 19: 327-328PubMed Google Scholar] or associated with prosthetic joints [7Weightman NC Allerton KE France J Bone and prosthetic joint infection with Staphylococcus lugdunensis.J Infect. 2000; 40: 98-99Abstract Full Text PDF PubMed Scopus (27) Google Scholar]. Vertebral osteomyelitis secondary to S. lugdunensis was first described in 1996 in an elderly woman undergoing long-term steroid treatment for polymyalgia rheumatica. A further case has been described in a man on steroids and methotrexate for rheumatoid arthritis [8Kragsbjerg P Bomfim-Loogna J Tornqvist E Soderquist B Development of antimicrobial resistance in Staphylococcus lugdunensis during treatment—report of a case of bacterial arthritis, vertebral osteomyelitis and infective endocarditis.Clin Microbiol Infect. 2000; 6: 496-499Crossref PubMed Scopus (29) Google Scholar]. There has been only one previously reported case of S. lugdunensis vertebral osteomyelitis in an immunocompetent patient that we are aware of [7Weightman NC Allerton KE France J Bone and prosthetic joint infection with Staphylococcus lugdunensis.J Infect. 2000; 40: 98-99Abstract Full Text PDF PubMed Scopus (27) Google Scholar]. CNS are important nosocomial pathogens. Infections due to CNS are increasing with the increased use of catheters and artificial devices. There are 32 species of CNS [9Archer GL Staphylococcus epidermidis and other coagulase-negative staphylococci.in: Mandell GL Bennett JE Dolin R Mandell, Douglas and Bennett's principles and practice of infectious diseases. 5th edn. Churchill Livingstone, Philadelphia2000: 2092-2100Google Scholar], 15 of which are indigenous to humans, and these are differentiated by a series of biochemical tests. Speciation is useful if there is an association between certain species and specific infections or antibiotic sensitivity patterns. Most laboratories only speciate CNS when there are multiple positive cultures. Many will also speciate CNS if the patient has an implanted artificial device. This is because CNS are frequent 'contaminants' in microbiological specimens and are thus frequently discounted as not significant. S. lugdunensis, unlike other CNS, is only rarely a contaminant [2Herchline TE Ayers LW Occurrence of Staphylococcus lugdunensis in consecutive clinical cultures and relationship of isolation to infection.J Clin Microbiol. 1991; 29: 419-421PubMed Google Scholar], and infections due to this organism often follow an aggressive course. For example, there are several cases of S. lugdunensis endocarditis reported in the literature [4Vandenesch F Etienne J Reverdy ME Eykyn SJ Endocarditis due to Staphylococcus lugdunensis: report of 11 cases and review.Clin Infect Dis. 1993; 17: 871-876Crossref PubMed Scopus (165) Google Scholar]. Unlike endocarditis caused by most CNS, S. lugdunensis endocarditis usually affects native, rather than prosthetic, heart valves and has an associated mortality of 50%. Many CNS are resistant to multiple antibiotics. However, S. lugdunensis often has a favorable antibiotic sensitivity pattern, as demonstrated by our case. Thus, there is good reason to differentiate S. lugdunensis from other CNS, and care must be taken before discounting a positive culture of CNS as a contaminant. This is particularly true when the bacteria are cultured from a surgical sample, which cannot easily be repeated. Such bacteria should be identified or at least conserved for several months for further identification if needed.
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