Staphylococcus capitis isolated from prosthetic joint infections

Abstract

Further knowledge about the clinical and microbiological characteristics of prosthetic joint infections (PJIs) caused by different coagulase-negative staphylococci (CoNS) may facilitate interpretation of microbiological findings and improve treatment algorithms. Staphylococcus capitis is a CoNS with documented potential for both human disease and nosocomial spread. As data on orthopaedic infections are scarce, our aim was to describe the clinical and microbiological characteristics of PJIs caused by S. capitis. This retrospective cohort study included three centres and 21 patients with significant growth of S. capitis during revision surgery for PJI between 2005 and 2014. Clinical data were extracted and further microbiological characterisation of the S. capitis isolates was performed. Multidrug-resistant (≥3 antibiotic groups) S. capitis was detected in 28.6 % of isolates, methicillin resistance in 38.1 % and fluoroquinolone resistance in 14.3 %; no isolates were rifampin-resistant. Heterogeneous glycopeptide-intermediate resistance was detected in 38.1 %. Biofilm-forming ability was common. All episodes were either early post-interventional or chronic, and there were no haematogenous infections. Ten patients experienced monomicrobial infections. Among patients available for evaluation, 86 % of chronic infections and 70 % of early post-interventional infections achieved clinical cure; 90 % of monomicrobial infections remained infection-free. Genetic fingerprinting with repetitive sequence-based polymerase chain reaction (rep-PCR; DiversiLab®) displayed clustering of isolates, suggesting that nosocomial spread might be present. Staphylococcus capitis has the potential to cause PJIs, with infection most likely being contracted during surgery or in the early postoperative period. As S. capitis might be an emerging nosocomial pathogen, surveillance of the prevalence of PJIs caused by S. capitis could be recommended.

Fig. 1

Staphylococcus capitis (n = 21) isolated from prosthetic joint infections (PJIs). The Congo red agar (CRA) results are compared to optical density (OD) values in the microtitre plate assay (MTP) in relation to the MTP cut-off; the CRA-negative isolates display a wide range of OD, while the majority of CRA-positive isolates cluster close to the cut-off

Fig. 2

Dendrogram created with DiversiLab® including information about centre (centre 1: n = 5, centre 2: n = 4, centre 3: n = 12), infection type, year of isolation, i.e. diagnosis of PJI (year of primary surgery), number of tissue cultures displaying growth of S. capitis/total number of cultures, total number of pathogens in significant amount (≥2 tissue cultures or ≥1 if highly pathogenic bacteria such as S. aureus), subspecies, methicillin sensitivity (met), heterogeneous glycopeptide-intermediate S. capitis (using the VAN4 screening method), multidrug-resistance (MDR) and biofilm-forming ability (CRA = Congo red agar, MTP = microtitre plate assay)

Fig. 3

Dendrogram created with DiversiLab® combined with the results of biochemical analyses from three simultaneously collected isolates from patient 1 during surgery. This infection was monomicrobial. U/Ma, urease/maltose; met, methicillin; cli, clindamycin; ery, erythromycin; nor, norfloxacin; cip, ciprofloxacin