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Evaluation of a sonication protocol for the detection of bacteria in retrieved osteosynthesis implants

Abstract number: P867

Esteban J., Cordero-Ampuero J., Adames H., Martín-de-Hijas N.Z., Ortiz-Perez A., Fernández-Roblas R., Sandoval E., Gómez-Barrena E.

Objectives: To evaluate the usefulness of a sonication protocol to detect the presence of bacteria in retrieved osteosynthesis implants from patients with and without clinical infection.

Methods: A sonication protocol previously developed by us was used in the experiment (Esteban J et al. J Clin Microbiol 2008; 46: 488–492). The protocol includes both low-power sonication during 5 minutes, centrifugation, the use of a broad spectrum of culture media (including specific media for fungi and mycobacteria), and quantitative evaluation of the results. Osteosynthesis implants were processed within 24 hours from surgical removal. Clinical diagnosis of infection was performed according internationally accepted schemes.

Results: Between July 2006 and November-2008, 63 samples from 47 patients (1.34 samples/patient) were processed. Samples included nails (23 samples), plates (10 samples), groups of screws (19 samples) and other osteosynthesis material (11 samples). 15 patients (21 samples) had a clinical diagnosis of infection. Among these cases, 17 samples gave positive results (77.3%). Bacteria isolated from these cases included 9 strains of S. aureus, 3 S. epidermidis, 2 Enterococcus sp., 2 S. intermedius, 1 S. maltophilia, 1 P. stuartii, 1 P. prevotii, and 3 cases with mixed anaerobic bacteria (>3 different species/sample). 8 cases had >1 isolates. Among the clinically non-infected patients (42 samples), 11 samples from 10 patients gave positive results (26.2%). Isolates included 1 Burkholderia sp., 2 M. fortuitum, 2 P. acnes (from the same patient), 1 R. pickettii, 1 S. paucimobilis, 2 S. epidermidis, 2 S. aureus, 1 C. parapsilosis and 1 Micrococcus sp. Two samples had >1 isolates. The average colony count was 69,927.08 CFU/ml for the samples from clinically infected patients (range: 50–100,000 CFU/ml) and 36,473.08 CFU/ml for clinically non-infected patients (range: 50–100,000 CFU/ml), a statistically significant difference (Student's T, p = 0.02).

Conclusions: The presented sonication protocol is a valuable tool for the isolation of bacteria from retrieved osteosynthesis implants. Patients without clinical infection can show higher counts of potentially pathogenic bacteria, although the average count is significatively lower than the average count of the patients with clinical infection. The clinical significance of low pathogenic organisms is doubtful, but they may not be considered as colonisation or contamination without further evaluations.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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