Same Organism, Different Phenotype - Are Phenotypic Criteria Adequate In Coagulase-Negative Staphylococcal Orthopaedic Implant-Associated Infections?

Staffan Tevell,Sharmin Baig,Åsa Nilsdotter-Augustinsson,Bo Söderquist,Marc Stegger

doi:10.7150/jbji.30256

Abstract

In current diagnostic criteria for implant-associated bone- and joint infections, phenotypically identical low-virulence bacteria in two intraoperative cultures are usually required. Using whole-genome sequencing, we have further characterized three phenotypically different Staphylococcus capitis isolated from one prosthetic joint infection, highlighting the challenges in defining microbiological criteria for low-virulence prosthetic joint infections.

Highlights

Orthopaedic implant-associated bone and joint infections such as prosthetic joint infections (PJIs) and fracture related infections (FRIs) are difficult both to diagnose and to treat
The implant was not further analysed, as sonication was unavailable at the laboratory. None of these three isolates were phenotypically identical according to antibiotic susceptibility testing, as one isolate (SCPJI10_1-1b) was sensitive to erythromycin, clindamycin, norfloxacin, and ciprofloxacin, the second (SCPJI10_1-1c) was resistant to erythromycin and clindamycin but sensitive to norfloxacin and ciprofloxacin, and the last isolate (SCPJI10_1-1a) was http://www.jbji.net resistant to erythromycin, clindamycin, and norfloxacin but sensitive to ciprofloxacin
We present a case of monomicrobial PJI, that initially was identified as polymicrobial since three phenotypically different isolates of S. capitis was found, later confirmed to be identical using whole-genome sequencing (WGS)

Summary

Introduction

Orthopaedic implant-associated bone and joint infections such as prosthetic joint infections (PJIs) and fracture related infections (FRIs) are difficult both to diagnose and to treat. The implant was not further analysed, as sonication was unavailable at the laboratory. None of these three isolates were phenotypically identical according to antibiotic susceptibility testing, as one isolate (SCPJI10_1-1b) was sensitive to erythromycin, clindamycin, norfloxacin, and ciprofloxacin, the second (SCPJI10_1-1c) was resistant to erythromycin and clindamycin but sensitive to norfloxacin and ciprofloxacin, and the last isolate (SCPJI10_1-1a) was http://www.jbji.net resistant to erythromycin, clindamycin, and norfloxacin but sensitive to ciprofloxacin. All other analyses were identical; the isolates were resistant to betalactam antibiotics and gentamicin, and susceptible to fusidic acid, rifampin, trimethoprim/sulfamethoxazole, linezolid and vancomycin (MIC 1.5 mg/L), but expressed heterogeneously intermediate susceptibility to glycopeptides according to the Van4-method [7]. The patient was cured using a two-stage revision including antibiotic treatment for three months (vancomycin followed by fluoroquinolone/rifampin combination)

Methods

Results

Conclusion