Plasmid-pattern analysis for the differentiation of infecting from noninfecting Staphylococcus epidermidis
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Published on: November 4, 2016
Abstract:
Isolation of Staphylococcus epidermidis from cultures of blood was differentiated from culture contamination by the detection of identical isolates in two or more consecutive cultures from an infected patient. We used plasmid-pattern analysis as a tool for establishing the identity of individual isolates. In a control study of 15 patients with two or more cultures of blood contaminated with S. epidermidis, analysis revealed that none of the isolates had identical plasmid patterns. This reflected the variety of plasmid patterns among colonizing coagulase-negative staphylococci cultured from skin sites of uninfected patients. In contrast, plasmid-pattern identity was seen among sequential or paired S. epidermidis isolates from a given patient in 32 of 36 patients with documented S. epidermidis infection. The plasmid pattern of each set of isolates from patients was unique. Infections included prosthetic-valve endocarditis in 26 patients, cerebrospinal fluid-shunt or ventriculostomy infections in six patients, intravenous-catheter sepsis in two patients, urinary tract infection in one patient, and osteomyelitis in one patient. Plasmid-pattern analysis may therefore be useful in the diagnosis of S. epidermidis infections.
Insights
Plasmid-pattern analysis helps distinguish true Staphylococcus epidermidis infections from blood culture contamination. Identical plasmid patterns in sequential cultures indicate infection, aiding accurate diagnosis.
Area of Science:
- Microbiology
- Infectious Diseases
- Molecular Diagnostics
Background:
- Staphylococcus epidermidis is a common cause of healthcare-associated infections.
- Differentiating true infection from blood culture contamination is clinically significant.
- Plasmid-pattern analysis offers a potential method for isolate identification.
Purpose of the Study:
- To evaluate the utility of plasmid-pattern analysis in differentiating Staphylococcus epidermidis bloodstream infections from contamination.
- To assess the discriminatory power of plasmid-pattern analysis in clinical isolates.
Main Methods:
- Plasmid DNA was extracted from Staphylococcus epidermidis isolates.
- Plasmid profiles were analyzed using gel electrophoresis.
- Isolates from sequential blood cultures of patients were compared.
Main Results:
- None of the isolates from contaminated blood cultures (n=15) showed identical plasmid patterns.
- Identical plasmid patterns were observed in sequential isolates from 32 of 36 patients with documented S. epidermidis infections.
- Each set of sequential isolates from infected patients exhibited a unique plasmid pattern.
Conclusions:
- Plasmid-pattern analysis is a valuable tool for distinguishing Staphylococcus epidermidis bloodstream infections from contamination.
- This method can aid in the accurate diagnosis of S. epidermidis infections, including prosthetic-valve endocarditis and shunt infections.
