Journal of infection (1997) 34, 113 118 Increasing Frequency of Vertebral Osteomyelitis following Staphylococcus aureus Bacteraemia in Denmark 1980-1990 A. G. Jensen ~, F. Espersen ~, P. Skinhoj 2, V. T. Rosdahl I and N. Frimodt-Moller ~ ~Sector for Clinical Microbiology, Statens Serum Institut, and 2Department of Infectious Diseases, Rigshospitalet, Copenhagen, Denmark Accepted for publication 18 August 1996 From 1980 to 1990, 309 cases of haematogenous osteomyelitis were identified in Denmark. Haematogenous osteomBelitis of the vertebral column increased significantly (P<O.01) from the first to the second half of the period due to an increased number of patients >50 years of age with communitB-acquired infection. Vertebral osteomgelitis differed significantly firm osteomgelitis of other bones in accordance to age distribution (median 66 vs. 16 years), male@male ratio (75/71 vs. 105/ 58) and patients with diabetes (13% vs. 6%). We found a higher risk of haematogenous osteomBelitis in patients >50 years of age and among patients with community-acquired i@ction. The highest incidence (5%) of vertebral osteomgelitis in Staphylococcus aureus bacteraemia in this age group was found in cases without an identified portal of entry. The highest incidence (34%) of osteomgelitis of other bones was found in communitg-acquired cases in the age group 1-20 gears and without an identified portal of entry. The present stu@ discusses reasons for the continued increase of vertebral osteom~delitis among adults and describes incidence rotes and major risk factors for developing haematogenous osteomgelitis among patients with S. aureus bacteraemia. We suggest that the localization of haematogenous S. aureus osteomgelitis is connected with the presence of red bone marmm Introduction Bacterial osteomyelitis, primarily due to Staphylococcus aureus infections, were previously most commonly found in younger patients. These mainly involved the long bones (i.e. femur, tibia, and humerus) and had a high rate of complications, first of all was the development of chronic infection. 1 3 After the introduction of antibiotics and the development of a range of modern diagnostic and thereapeutic principles, the rate of chronic infections has decreased. 4-z The incidence of infections of the long bones associated with S. aureus bacteraemia seems, how- ever, to have decreased, and instead there has been an increasing frequency of haematogenous osteomyelitis of the vertebral column. 3' 6 s Recently, we reviewed 525 cases of acute haemato- genous S. aureus osteomyelitis in Denmark from 1959 to 1988 and found a possible increase in the number of older patients with osteomyelitis of the vertebral column in recent years. 7 In the present study, we focused on the more recent occurrence of osteomyelitis of the vertebral column and describe the epidemiology of this infection *Address correspondence to: Allan G. Jensen, Building 45, Sector for Clinical Microbiology, Statens Serum Institut, Artillerivej 5, DK-2300 Copenhagen S, Denmark. compared to other cases of osteomyelitis and the re- maining S. aureus bacteraemia cases. Patients and Methods Organization Since 1956 the Staphylococcus Laboratory at Statens Serum Institut, Copenhagen, has carried out a con- tinuous, nationwide registration of S. aureus infections in Denmark. Nearly all S. aureus strains isolated from blood cultures in Denmark have been referred to this de- partment for phage typing. Clinical information has been obtained in all but a few cases. 9 1~ For the present study, data from the period 1980-1990 were used. Clinical data The following data have been recorded: age and sex of the patient; whether the patient had diabetes mellitus; if the infection was either hospital-acquired, community- acquired or unclassified; survival or death of the patient; and the portal of entry. The portal of entry was determined to be either present, if a primary focus (skin, intravenous catheter, wound etc.) was identified, or absent if no 0163-4453/97/020113 + 06 $12.00/0 © 1997 The British Society for the Study of Infection