Lack of microbiological concordance between bone and non-bone specimens in chronic osteomyelitis: an observational study

BMC Infectious Diseases BMC 2002,Infectious Diseases 2 Research article BioMed Central x Lack of microbiological concordance between bone and non-bone specimens in chronic osteomyelitis: an observational study Andrés F Zuluaga, Wilson Galvis, Fabián Jaimes and Omar Vesga* Address: Section of Infectious Diseases, Department of Medicine, University of Antioquia Medical School and Hospital Universitario San Vicente de Paul, Medellín, Colombia E-mail: Andrés F Zuluaga - ; Wilson Galvis - ; Fabián Jaimes - ; Omar Vesga* - *Corresponding author Published: 16 May 2002 BMC Infectious Diseases 2002, 2:8 Received: 20 December 2001 Accepted: 16 May 2002 This article is available from: http://www.biomedcentral.com/1471-2334/2/8 © 2002 Zuluaga et al; licensee BioMed Central Ltd. Verbatim copying and redistribution of this article are permitted in any medium for any purpose, provided this notice is preserved along with the article's original URL. Abstract Background: Prognosis of chronic osteomyelitis depends heavily on proper identification and treatment of the bone-infecting organism. Current knowledge on selecting the best specimen for culture is confusing, and many consider that non-bone specimens are suitable to replace bone cultures. This paper compares the microbiology of non-bone specimens with bone cultures, taking the last as the diagnostic gold standard. Methods: Retrospective observational analysis of 50 patients with bacterial chronic osteomyelitis in a 750-bed University-based hospital. Results: Concordance between both specimens for all etiologic agents was 28%, for Staphylococcus aureus 38%, and for organisms other than S. aureus 19%. The culture of non-bone specimens to identify the causative organisms in chronic osteomyelitis produced 52% false negatives and 36% false positives when compared against bone cultures. Conclusions: Diagnosis and therapy of chronic osteomyelitis cannot be guided by cultures of nonbone specimens because their microbiology is substantially different to the microbiology of the bone. Background Chronic osteomyelitis (COM) is a major medical problem in most countries, mainly associated with violent trauma and modern surgery. It is a very expensive disease for patient and society because of the involved costs of diagnosis, inpatient and outpatient treatment, rehabilitation, lost productivity, and sequelae [1]. In the opinion of authorized clinicians, the term cure cannot be applied to COM, because "the bone infection may recur years after apparently successful treatment of the disease" [2]. To minimize risk of recurrence, treatment must include thor- ough surgical debridement and precise antimicrobial therapy directed against the pathogen involved in the infection. Based on common sense and a single classical paper [3], appropriate cultures of bone specimens are considered the gold standard for conclusive microbiological diagnosis [2,4,5]. However, recent studies suggest that microorganisms isolated from non-bone specimens such as sinus tracts and superficial wounds are concordant with those found in bone specimens, and conclude that these samples are as good as the infected bone [6–8]. In consequence, orthopedic surgeons prefer non-bone to bone Page 1 of 7 (page number not for citation purposes) BMC Infectious Diseases 2002, 2 specimens to guide antimicrobial therapy in many instances of suspected COM, particularly after complicated reconstructive bone surgery. Although most experts [4,5,9] and new studies [10] keep emphasizing the importance of bone cultures as the diagnostic gold standard, these conflicting reports suggest the necessity of more and better data, because confusion may have been feeding further the no cure theory [9]. Chronic and acute osteomyelitis related to trauma by high-speed bullets, bomb explosions and car accidents particularly affects Colombia, a developing country with an old internal conflict. Although reliable official statistics do not exist, prevalence might be illustrated by the fact that 10% of 1500 consults/year to the Infectious Diseases Section at our institution are caused by osteomyelitis. For the last four years, we have worked together with orthopedic surgeons in the management of osteomyelitis: besides proper surgical debridement-including excision of inert and foreign material- and obliteration of dead space left by such procedure, accurate identification and susceptibility pattern of the infecting organism in the bone are required elements to start antimicrobial therapy. This paper reports the findings of a retrospective cross-sectional observational analysis of 50 patients with confirmed COM who had cultures from bone and non-bone specimens. The aim of the study was to establish how often the microbiology of non-bone specimens was concordant with that of the diagnostic gold standard (culture of operative bone specimens). Methods Setting and design The study was conducted at Hospital Universitario San Vicente de Paul, a 750-bed, third level university-based hospital located in Medellín, Colombia. From February 1998 to August 2001 all charts from patients with confirmed COM recorded in the Infectious Diseases Section database were screened for inclusion and exclusion criteria. For clinical records and database entry purposes, COM had been defined since 1997 as a bone infection that was worst or had not improved after one month of evolution, independent of the presence or quality of surgical and antimicrobial therapy. This definition was selected because one month is 3 times the 10-day period necessary for bone necrosis after acute infection [11] and it allowed precise selection of patients from the database. To overcome the limitation imposed by the lack of bone histopathology demonstrating COM, each case was evaluated in search of the hallmark of chronicity, that is, bone necrosis, microorganisms infecting the bone, and compromised soft tissues surrounding the infected bone [12]. http://www.biomedcentral.com/1471-2334/2/8 Inclusion and exclusion criteria Inclusion criteria allowed patients of any age and gender with COM as defined above, who had aerobic bacterial cultures from the infected bone and from any of the following non-bone specimens directly related to the infected bone: pus aspirated from surrounding soft tissues, soft tissues, surgical wounds, drainage from orifices left by orthopedic pins, and drainage from sinus tracts. Only four operative bone specimens were acceptable: bone biopsy, sequestrum, bone marrow, and aspirated subperiostic pus. It was also required that bone specimens had to be taken during surgery, and a clear note by the surgeon must establish if the incision was made through intact skin in opposition to infected soft tissues or sinus tracts. Nonbone specimens could be taken during surgery or in the ward, by needle aspiration, sterile swab, or soft tissues biopsy. Patients with COM secondary to diabetic foot or decubitus ulcers were excluded to allow the a (...truncated)