Hematogenous vertebral osteomyelitis due to Staphylococcus aureus in the adult.

Hematogenous vertebral osteomyelitis (HVO) is becoming increasingly common in the developed Western countries. An aging population, frequent use of intravascular catheters for diagnostic and therapeutic procedures with complicating bacteremia, hemodialysis, frequent invasive procedures, and IV drug abuse are important predisposing factors. (1) Staphylococcus aureus is the most important pathogen in HVO. (2) Methicillin-resistant strains of S aureus now constitute the majority of nosocomial isolates in the United States and have recently become widespread in the community as well. (3) With an increase in methicillin-resistant Staphylococcus aureus (MRSA) bacteremia, cases of MRSA HVO are likely to become more frequent, with vancomycin being increasingly utilized in the treatment of HVO. Vancomycin monotherapy of MRSA HVO is recommended in a standard infectious diseases textbook and in a recent review of osteomyelitis; (4,5) however, we have reported a series of patients who developed MRSA HVO with neurologic complications while receiving vancomycin monotherapy for MRSA bacteremia. (6) So what is the optimal antibiotic therapy for a patient with MRSA HVO?

In this issue of the Journal, Priest and Peacock report a retrospective chart review series of 40 patients with S aureus HVO from a single medical center. (7) Thirteen out of 40 patients were infected with MRSA.

A number of useful and practical points are contained in this review. The authors confirmed the importance of age, intravascular devices, diabetes, and hemodialysis in the pathogenesis of S aureus HVO. Aggressive therapy of IV catheter-related bacteremia is important in preventing S aureus HVO. The duration of therapy of S aureus HVO is controversial. The authors propose that their strategy of 8 weeks of IV antibiotic in combination with rifampin resulted in a favorable outcome in the majority of patients. They did however treat many patients with a prolonged course of oral antibiotics as well. Neither a rifampin-based regimen nor a strategy of prolonged antibiotic therapy have been subjected to a controlled study, but both appear reasonable and are favored by many infectious disease specialists.

In this series, patients infected with MRSA suffered from higher all-cause and infection-related mortality than the patients infected with methicillin-sensitive Staphylococcus aureus (MSSA). This difference was statistically significant.

The design of this study does not allow us to determine whether higher MRSA HVO mortality was secondary to patient-related or pathogen-related factors. MRSA strains with decreased susceptibility to vancomycin and therapeutic failures of vancomycin in MRSA infections, including osteomyelitis, are increasingly being reported. (8) The strategy of adding rifampin to vancomycin employed by Priest and Peacock is an attractive option. Synergy and the superior tissue penetration of rifampin may render this regimen superior to vancomycin monotherapy. Other possible alternatives for the treatment of MRSA HVO include linezolid, daptomycin, or various combinations of available agents. Whether these will prove to be superior to vancomycin remains to be determined.

S aureus HVO remains a challenging disease and the paper by Priest and Peacock will assist the clinician in diagnosing and treating this condition.

References

1. Jensen AG, Espersen F, Skinhoj P, Fromodt-Moller N. Bacteremic Staphylococcus aureus spondylitis. Achlntern Med 1998;158:509-517.

2. McHenry MC, Easley KA, Locker GA. Vertebral osteomyelitis: long-term outcome for 253 patients from 7 Cleveland-area hospitals. Clin Infect Dis 2002;34:1342-1350.

3. Deresinski S. Methicillin-resistant Staphylococcus aureus: an evolutionary, epidemiologic, and therapeutic odyssey. Clin Infect Dis 2004;40:562-573.

4. Berbari EF, Steckelberg JM, Osmon DR. Osteomyelitis. In Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. Philadelphia, Churchill Livingstone, ed 6, pp 1322-1332.

5. Waldvogel FA, Lew DP. Osteomyelitis. Lancet 2004;364:369-379.

6. Gelfand MS, Cleveland KO. Vancomycin therapy and the progression of methicillin-resistant Staphylococcus aureus vertebral osteomyelitis. South Med J 2004;97:593-597.

7. Priest DH, Peacock JE. Hematogenous vertebral osteomyelitis due to Staphylococcus aureus in the adult: clinical features and therapeutic outcomes. South Med J 2005;98:854-862.

8. Howden BP, Ward BP, Charles PGP, et al. Treatment outcomes for serious infections caused by methicillin-resistant Staphylococcus aureus with reduced susceptibility to vancomycin. Clin Infect Dis 2004;38:521-528.

Michael S. Gelfand, MD, Kerry O. Cleveland, MD

Reprint requests to Kerry O. Cleveland, MD, University of Tennessee, Department of Medicine, Division of Infectious Diseases, 956 Court Avenue, Room H308, Memphis, TN, 38263. Email: [e-mail]

Accepted May 12, 2005.