Use of Genotypic Identification by sodA Sequencing in a Prospective Study To Examine the Distribution of Coagulase-Negative Staphylococcus Species among Strains Recovered during Septic Orthopedic Surgery and Evaluate Their Significance

Abstract

A total of 212 coagulase-negative Staphylococcus strains recovered prospectively during 119 surgeries for proven or suspected bone and joint infection (BJI) were identified by sodA sequencing. These strains were identified as 151 Staphylococcus epidermidis isolates, 15 S. warneri isolates, 14 S. capitis isolates, 9 S. hominis isolates, 6 S. lugdunensis isolates, 5 S. haemolyticus isolates, 4 S. caprae isolates, 4 S. pasteuri isolates, 3 S. simulans isolates, and 1 S. cohnii isolate. Only S. epidermidis, S. lugdunensis, S. capitis, and S. caprae were found to be infecting organisms and were involved, respectively, in 35 (81.4%), 3 (7.0%), 3 (7.0%), and 2 (4.6%) cases of BJI.Coagulase-negative Staphylococcus (CoNS) strains are a leading cause of arthroplastic infections, accounting for 15 to 37.5% of isolates recovered from peroperative samples (13). Staphylococcus epidermidis is the main species responsible for these infections and for other device-related bone and joint infections (BJI). There are some reports of true BJI caused by CoNS species other than S. epidermidis, including S. caprae (1), S. lugdunensis (24), and S. simulans (18). However, no prospective study has specifically addressed the species distribution of CoNS strains in BJI. Identification of CoNS strains to the species level has long been an obstacle preventing this question from being answered satisfactorily. PCR-based sequencing methods can now accurately identify a wide spectrum of Staphylococcus species (7,11,17). In this 4-year prospective study, we used sodA sequencing to identify CoNS species associated with BJI.All surgical procedures performed in the orthopedic department of Raymond Poincaré hospital (Garches, France) between January 1999 and December 2002 for proven or suspected BJI were studied prospectively. We included all procedures in which at least three independent samples were collected during the same operative procedure, at least one sample was positive for a CoNS strain, and no samples were positive for organisms other than CoNS strains. The samples were processed in a class 2 laminar-flow safety cabinet. A portion of the sample was Gram stained, and the remainder was used to inoculate 10 ml of Schaedler broth (BioMérieux, Marcy l'Etoile, France). After agitation, aliquots were used to inoculate chocolate agar plates (incubated in 5% CO 2 ) and blood agar plates (incubated aerobically and anaerobically). The plates were examined daily for 7 days. Broths were subcultured after 1 and 5 days. The "CoNS group" was identified by Gram staining, catalase testing, Slidex latex agglutination testing (BioMérieux), and tube coagulase testing (Bio-Rad, Marnes la Coquette, France). Antibiotic susceptibility was evaluated by the disk diffusion method on Mueller-Hinton agar (Bio-Rad). Strains were identified to the species level by partial sodA sequencing (17) as described recently by our group (21). We used the definitions and criteria recommended by the OSIRIS (Oxford Skeletal Infection Research and Intervention Service) group (2). CoNS...

tuf Gene Sequence Analysis Has Greater Discriminatory Power than 16S rRNA Sequence Analysis in Identification of Clinical Isolates of Coagulase-Negative Staphylococci

“…Although this method is widely used and accurate, the high degree of similarity between closely related species limits its usefulness for identifying several CNS species (27). Alternative target genes, such as rpoB, tuf, dnaJ, and sodA, are being assessed for their abilities to distinguish between highly similar species (12,14,15,24,27,28). The tuf gene, which encodes the elongation factor Tu, is an essential constituent of the bacterial genome and is involved in peptide chain formation.…”

Decreased Susceptibility to Teicoplanin and Vancomycin in Coagulase-Negative Staphylococci Isolated from Orthopedic-Device-Associated Infections

“…Resistance of CoNS to glycopeptides may, however, be a major problem in this context. CoNS are the main cause of prosthetic joint infections and other device-related bone and joint infections (BJIs) (12,16). Most strains are resistant to methicillin and other drugs commonly used for the treatment of BJIs, leading to an increase in the use of glycopeptides (23).…”

Identification of Coagulase-Negative Staphylococci by SodA Gene Sequence Analysis

“…The increasing significance of CoNS serves the justification for a more accurate species identification to allow a precise determination of host-pathogenic potential of each of the various CoNS species (Heikens et al, 2005;Poyart et al, 2001;Sivadon et al, 2005). Various methods have been proposed, both phenotypically and genotypically.…”