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Investigation of a Streptococcus viridans pseudobacteremia epidemic at a university teaching hospital
1Department of Microbiology, University of Calgary, Alberta, Canada.
Abstract:
For several months in 1986, an outbreak of Streptococcus viridans pseudobacteremia occurred at a large teaching hospital. All sources of laboratory blood culture contamination were excluded. A retrospective epidemiological study indicated that one phlebotomist, "P," collected a disproportionate number of the positive blood cultures. Further comparison of the paired blood culture results from the three months when the incidence was highest revealed a good concordance of results among all other phlebotomists (Kappa = 0.5), while P's results concurred with others less frequently than would be expected even by chance (Kappa less than 0.0). Clinical follow-up showed that P did not routinely wear gloves while drawing blood and had eczema of the hands. Skin scrapings from the hands, right index finger/fingernail grew predominantly S viridans species that were compatible with those recovered from contaminated blood cultures. This epidemic demonstrated the need for early detection of this source as a cause of nosocomial pseudobacteremia.
Insights
A healthcare worker
Area of Science:
- Clinical Microbiology and Infectious Diseases
- Hospital Epidemiology and Infection Control
Background:
- An outbreak of Streptococcus viridans pseudobacteremia occurred at a teaching hospital.
- Laboratory contamination was ruled out as the source.
Purpose of the Study:
- To identify the source of the recurrent pseudobacteremia outbreak.
- To investigate the role of a specific phlebotomist in the outbreak.
Main Methods:
- Retrospective epidemiological study.
- Analysis of blood culture results and phlebotomist concordance.
- Microbiological analysis of skin scrapings from a phlebotomist's hands.
Main Results:
- One phlebotomist was disproportionately associated with positive blood cultures.
- Statistical analysis showed poor concordance between this phlebotomist's results and others.
- Skin scrapings from the phlebotomist's hands yielded Streptococcus viridans, matching isolates from blood cultures.
Conclusions:
- The phlebotomist's hand hygiene practices (lack of gloves, eczema) likely led to S. viridans contamination.
- This case highlights the importance of identifying personnel as a source of nosocomial pseudobacteremia.
- Early detection and intervention are crucial to control such outbreaks.
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