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Role of the Staphylococcus epidermidis slime layer in experimental tunnel tract infections
C C Patrick1, M R Plaunt, S V Hetherington
1Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee.
Abstract:
An experimental animal model was used to assess the slime layer of Staphylococcus epidermidis as a pathogenic factor in tunnel tract infections. Mice were inoculated with high-slime-producing or non-slime-producing strains of S. epidermidis, either along the length of a subcutaneous catheter or in the area where a catheter had been placed and immediately removed (controls). Among the catheter-bearing mice, the phenotypically distinct staphylococci produced similar, high frequencies of abscess formation (72% [44 of 61] versus 81% [31 of 38]; P = 0.29). In controls, the non-slime-producing organisms were significantly more pathogenic (87% [40 of 46] versus 57% [25 of 44] abscess formation; P = 0.001). No consistent difference was detected between blood isolates obtained from patients with central venous catheter bacteremia and those from neonates with bacteremia in the absence of a prosthetic medical device. Quantitative culture of removed catheters showed greater adherence by the slime-producing isolates (P = 0.014). In this mouse model, slime production by S. epidermidis did not increase the risk of catheter tunnel tract infection, despite the greater catheter adherence of the slime-producing organisms. These findings suggest that traumatized tissue may be a sufficient condition for the development of S. epidermidis catheter-associated infections.
Insights
Staphylococcus epidermidis slime production did not increase catheter tunnel infections in mice. Traumatized tissue alone may be sufficient for developing these common S. epidermidis infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Medical Devices
Background:
- Staphylococcus epidermidis is a common cause of catheter-associated infections.
- The role of bacterial slime layers in the pathogenicity of S. epidermidis infections is not fully understood.
Purpose of the Study:
- To investigate the pathogenic role of the slime layer produced by S. epidermidis in catheter tunnel tract infections using an experimental animal model.
- To determine if slime production influences abscess formation and bacterial adherence to catheters.
Main Methods:
- An experimental animal model using mice was employed.
- Mice were inoculated with high-slime-producing or non-slime-producing strains of S. epidermidis along subcutaneous catheters or in control areas.
- Abscess formation and bacterial adherence to catheters were quantified.
Main Results:
- Slime-producing and non-slime-producing S. epidermidis strains caused similar high frequencies of abscess formation in catheter-bearing mice.
- In control groups, non-slime-producing strains were significantly more pathogenic.
- Slime-producing isolates showed greater adherence to removed catheters.
Conclusions:
- Slime production by S. epidermidis did not increase the risk of catheter tunnel tract infection in this mouse model.
- Greater adherence of slime-producing organisms to catheters did not translate to increased infection risk.
- These findings suggest that traumatized tissue may be a sufficient condition for S. epidermidis catheter-associated infections.