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Abstract & Commentary
Impact of Prebiopsy Antibiotics on Pathogen Recovery in Vertebral Osteomyelitis
By Dean L. Winslow, MD, FACP, FIDSA, Chief, Division of AIDS Medicine, Santa Clara Valley Medical Center; Clinical Professor, Stanford University School of Medicine, is Associate Editor for Infectious Disease Alert.
Dr. Winslow is a speaker for Cubist pharmaceuticals and GSK, and is a consultant for Siemens Diagnostic.
Synopsis: Ninety-two patients with hematogenous vertebral osteomyelitis underwent biopsy. Pathogens were recovered in 61 patients (66%). Open biopsy yielded a pathogen in 91% of cases and needle biopsy in 53%. Open biopsy predicted positive biopsy culture results, but there was no association with prebiopsy antibiotic administration.
Source: Marschall J, et al. The impact of prebiopsy antibiotics on pathogen recovery in hematogenous vertebral osteomyelitis. CID 2011;52:867-872.
Of 150 patients with hematogenous vertebral osteomyelitis, 92 (61%) underwent biopsy 60 (65%) needle and 32 (35%) open. Imaging studies revealed discitis in 75%, vertebral osteomyelitis in 70%, and epidural abscess in 44% of patients. Patients undergoing open biopsy were more likely to have neurologic symptoms and signs (29% vs. 10%) and epidural abscess on imaging studies, but were less likely to have a positive blood culture (30% vs. 52%). Sixty patients (65% of the patients undergoing biopsy) received antibiotics ≤ 14 days before the procedure (median, 4 days). Of the 92 patients who underwent biopsy, 34% of samples were culture-negative, 28% grew MSSA, 25% MRSA, 15% coagulase-negative staphylococci, and 7% E. coli. Open biopsy predicted positive biopsy culture results (91% positive on open biopsy vs. 53% on needle biopsy), but there was no association with prebiopsy antibiotic administration.
One of the pet peeves of most Infectious Diseases consultants is the rush of inexperienced clinicians to administer empiric antibiotics to clinically stable patients with chronic or subacute infections (particularly infective endocarditis and osteomyelitis) prior to obtaining appropriate cultures. A common scenario involves a well-meaning ER doctor or Internal Medicine house officer making an appropriate diagnosis of one of these conditions and then initiating empiric therapy (generally with "VoSyn" as one of our excellent Stanford ID Fellows refers to the commonly prescribed combination of vancomycin plus piperacillin/tazobactam) prior to obtaining appropriate material for culture to determine the exact pathogens involved. Often this results in committing the patient to 6 or more weeks of excessively broad spectrum or multiple empiric antibiotics given intravenously by PICC (with all of the attendant potential complications of prolonged broad-spectrum intravenous antibiotic therapy). If a highly sensitive pathogen were obtained prior to antibiotic administration, a narrow spectrum, and possibly oral, antibiotic regimen could have been used.
This study has a number of limitations including the following:
I believe the only way this study will alter my own practice is that I will push a little harder for biopsy (either by a surgeon or by interventional radiology) in patients who have received prior antibiotics, rather than just throwing up my hands and recommending broad spectrum antibiotics. While reassuring that it is still possible to obtain a pathogen by culture of a bone biopsy specimen in about two-thirds of cases after the patient has received several days of antibiotics, this does not mean that this is optimal practice. In most cases, culture of a bone biopsy specimen should still be obtained prior to starting antibiotics in clinically stable patients.