Subcutaneous abscess formation around catheters induced by viable and nonviableStaphylococcus epidermidis as well as by small amounts of bacterial cell wall components

Abstract

The use of catheters is often complicated by infection, mainly due to Staphylococcus epidermidis. Recently, a novel poly(vinylpyrrolidone)-grafted silicone elastomer catheter (SEpvp) was introduced. Less bacteria adhered to SEpvp than to conventional SE catheters in vitro. The frequency of S. epidermidis infection associated with SEpvp and SE was assessed in a rabbit model. Unexpectedly, abscesses were induced by the injection of low numbers of S. epidermidis along subcutaneously inserted SEpvp. No abscesses were seen around SE, even when very high numbers of S. epidermidis were injected. This bioincompatibility reaction observed around the SEpvp was independent of the host, bacterial strain, and method of inoculation. Abscesses were also induced by nonviable S. epidermidis and by bacterial cell wall components. Because these incompatibility reactions were not observed in the absence of bacteria, biocompatibility testing should include experiments in which the inflammatory effects of the combination of catheter and (non)viable bacteria are tested.

Enhanced Susceptibility to Subcutaneous Abscess Formation and Persistent Infection around Catheters Is Associated with Sustained Interleukin-1β Levels

“…This is in accordance with other studies (8,19). Biomaterials like SEpvp, which can be regarded as biocompatible in the absence of bacteria, can enhance the inflammatory reaction in the presence of bacteria, resulting in abscess formation and persistent infection (3). As a sustained IL-1␤ level was associated with persistent infection, IL-1 may be a marker for testing bioincompatibility in vitro or in vivo.…”

“…It is assumed that bacterial adherence is the initial step, but alterations in the host response may also play a role in the pathogenesis of catheter-associated infection (CAI) (2,6,18). Around a novel polyvinylpyrrolidone-grafted silicon elastomer catheter (SEpvp) (Bioglide; Medtronic PS Medical, Goleta, Calif.) developed to reduce bacterial adherence, abscesses and persistent infection were observed in rabbits and mice (3) in the presence of low numbers of S. epidermidis. Although the number of adherent bacteria found in vitro on a conventional silicon elastomer catheter (SE) (Medtronic PS Medical) was nine times higher than on SEpvp (4), no SE-associated infection developed.…”

“…They were divided into seven groups of 24 mice each and one group of 8 mice (baseline controls). Two groups received SE segments and two groups received SEpvp segments, implanted subcutaneously under antiseptic conditions, as described previously (3). Two groups of mice received sham operations (sham controls).…”

Interleukin-1 Receptor Type I Gene-Deficient Mice Are Less Susceptible toStaphylococcus epidermidisBiomaterial-Associated Infection than Are Wild-Type Mice

“…An inoculum of 10 6 CFU of S. epidermidis RP62a was used. We previously demonstrated that in mice injected with this inoculum along subcutaneously implanted SEpvp, macroscopic abscesses and persistent infection for up to at least 60 days were induced, while around SE neither abscess formation nor infection was observed (6,9). Two milliliters of an overnight culture of strain RP62a in Trypticase soy broth (Difco, Detroit, Mich.) was inoculated into 100 ml of fresh Trypticase soy broth.…”

“…Subsequently, the skin and subcutaneous tissue were separated from the muscle fascia up to the flank on both sides. The implantation sites were inspected for purulence, and standardized biopsies (diameter, 12 mm) were taken from the implantation sites using a specially developed tissue sampler as described previously (6). Each single biopsy included skin, subcutaneous tissue, and the inserted segment.…”