ABSTRACT
BACKGROUND: The significance of Staphylococcus epidermidis positive blood cultures is difficult to determine, but repeated isolation of the same organism with the same genotype is suggestive of true bacteremia. MATERIALS AND METHODS: Two sequential isolates of S. epidermidis from blood cultures of the same twelve patients were genotyped by PFGE. The results were compared with those of antibiotyping and isolation time intervals between the two strains. RESULTS: The two sequential strains from each patient had identical PFGE patterns in 66.6% (8 of 12) of the patients and two different types in 33.3% (4 of 12) of the patients. Antibiotypes of the two isolates from the same patient were different in all 4 patients whose isolates had different PFGE patterns, and they were the same in 7 of 8 patients whose isolates had identical PFGE patterns:the PFGE results were in agreement with the antibiotyping for 91.7% (11/12) of patients. The isolation time interval between the two strains was or =5 days. CONCLUSION: These data showed that two consecutive isolates of S. epidermidis from blood cultures had different PFGE patterns in 33% of patients, suggesting a high prevalence of contamination. In the absence of genotyping measures, both antibiotype and isolation time interval can be alternative and useful tools for determining strain relatedness of sequential isolates of S. epidermidis from blood cultures.
Subject(s)
Humans , Bacteremia , Electrophoresis, Gel, Pulsed-Field , Genotype , Prevalence , Staphylococcus epidermidis , StaphylococcusABSTRACT
BACKGROUND: The significance of Staphylococcus epidermidis positive blood cultures is difficult to determine, but repeated isolation of the same organism with the same genotype is suggestive of true bacteremia. MATERIALS AND METHODS: Two sequential isolates of S. epidermidis from blood cultures of the same twelve patients were genotyped by PFGE. The results were compared with those of antibiotyping and isolation time intervals between the two strains. RESULTS: The two sequential strains from each patient had identical PFGE patterns in 66.6% (8 of 12) of the patients and two different types in 33.3% (4 of 12) of the patients. Antibiotypes of the two isolates from the same patient were different in all 4 patients whose isolates had different PFGE patterns, and they were the same in 7 of 8 patients whose isolates had identical PFGE patterns:the PFGE results were in agreement with the antibiotyping for 91.7% (11/12) of patients. The isolation time interval between the two strains was or =5 days. CONCLUSION: These data showed that two consecutive isolates of S. epidermidis from blood cultures had different PFGE patterns in 33% of patients, suggesting a high prevalence of contamination. In the absence of genotyping measures, both antibiotype and isolation time interval can be alternative and useful tools for determining strain relatedness of sequential isolates of S. epidermidis from blood cultures.