Characterization of Staphylococcus epidermidis and Staphyloccocus warneri small-colony variants associated with prosthetic-joint infections

Abstract

We determined the frequency of isolation of staphylococcal small-colony variants (SCVs) from 31 culture-positive patients undergoing revision of total hip prosthesis for aseptic loosening or presumed prosthetic-joint infection (PJI). We analysed auxotrophy of cultured SCVs, their antimicrobial susceptibility profiles and their biofilm-forming capacity. Eight SCV strains were cultivated from six (19 %) patients. All SCVs were coagulase-negative staphylococci (CNS) with Staphylococcus epidermidis as the predominant species; there was also one Staphylococcus warneri SCV. The SCVs were auxotrophic for haemin, with one strain additionally auxotrophic for menadione. We noted the presence of two phenotypically (differences concerning antimicrobial susceptibility) and genetically distinct SCV strains in one patient, as well as the growth of two genetically related SCVs that differed in terms of their morphology and the type of auxotrophy in another. Seven out of eight SCVs were resistant to meticillin and gentamicin. In addition, antibiotic sensitivity testing revealed three multidrug-resistant SCV-normal-morphology isolate pairs. One S. epidermidis SCV harboured icaADBC genes and was found to be a proficient biofilm producer. This paper highlights the involvement of CNS SCVs in the aetiology of PJIs, including what is believed to be the first report of a S. warneri SCV. These subpopulations must be actively sought in the routine diagnosis of implant-associated infections. Moreover, in view of the phenotypic and genetic diversity of some SCV pairs, particular attention should be paid to the investigation of all types of observed colony morphologies, and isolates should be subjected to antimicrobial susceptibility testing.

The role of programmed death ligand 1 pathway in persistent biomaterial-associated infections

“…The relationship between the WT and their corresponding SCV strains were assessed with the use of a commercially available DNA fingerprinting assay based on the rep-PCR technology (data not shown). The bacterial strains used in this study are precisely characterized in our previous publication (Bogut et al, 2014). Characterization of the bacterial strains included in this study is presented in Table 1.…”

Clinical Significance and Pathogenesis of Staphylococcal Small Colony Variants in Persistent Infections

“…Unusually for the staphylococcal SCV phenotype, this stable SCV was strongly adherent to solid agar media, similar to sticky colonies formed by Rothia mucilaginosa (Stomatococcus mucilaginosus). Some SCV observations have been described for coagulase-negative staphylococcal (CoNS) species, particularly for S. epidermidis, S. capitis, and S. warneri, mostly in association with foreign bodyrelated infections (3,(19)(20)(21)(22)(23)(24). Also, for S. lugdunensis, a coagulasenegative species with a unique status almost resembling S. aureus in some aspects (25), SCVs have been reported for pacemakerrelated and prosthetic joint infections (PJIs) (20,26).…”

“…During a 22-month prospective study, Bogut et al studied cases of PJI according to the definition of Parvizi et al (24), which includes clear infective signs, such as a sinus tract communicating with the prosthesis, a pathogen isolated from two separate tissue samples or fluids, and elevated C-reactive protein (CRP) and elevated leukocyte counts in the synovial fluid. Nineteen patients met the criteria for PJI, and 12 patients met the critera for the diagnosis of aseptic loosening (AL).…”

Biofilm Producing Staphylococcus epidermidis Strains Isolated From Clinical Samples in Tehran, Iran

“…polymerase chain reactions were employed for detection of icaA, icaB, icaC, icaD, app, IS256, atlE and bhp genes by specific primers, as described previously (10,(18)(19)(20)(21).…”