Infection and Contamination Rate of Staphylococcus epidermidis in Blood Culture in Faculty of Medicine Vajira Hospital

Abstract

Infection and Contamination Rate of Staphylococcus epidermidis in Blood Culture in Faculty of Medicine Vajira Hospital

Uraporn Phumisantiphong MSc*

Dussadee Duangmanee MSc**

Uraiwan Tarunotai MD***

* Department of Clinical Pathology

** Infectious Control Unit

*** Department of Pediatrics

Faculty of Medicine Vajira Hospital, University of Bangkok Metropolis

Objectives: To determine the infection and contamination rates of Staphylococcus epidermidis (S. epidermidis) in patients whose hemocultures were positive for S. epidermidis and to compare the antimicrobial sensitivity of S. epidermidis between both groups.

Methods: This was a prospective descriptive study based on the identification of S. epidermidis isolated from 4,523 blood samples obtaining from 2,573 patients in the Faculty of Medicine Vajira Hospital. The study was undertaken from May 1, to July 16, 2010. The rates of infection or contamination were determined using clinical data of the patients and laboratory data. The antimicrobial sensitivity of S. epidermidis between bloodstream infections and contamination were compared.

Results: The rate of positive culture among 4,523 blood samples was 12.0% (542 isolates). S. epidermidis was the most common bacteria isolated (181 isolates or 33.4%). The infection rate and the contamination rate from patients with positive blood culture for S. epidermidis were 9.8% and 90.2% respectively. The prevalence of S. epidermidis contamination from all 4,523 specimens collected was 3.2%. The S. epidermidis isolated from contamination showed significantly higher sensitivity to almost all antimicrobial agents than those from infection.

Conclusion: There was a high contamination rate of blood cultures from S. epidermidis. Healthcare workers should consider the restriction and compliance on blood culture strategies to decrease blood culture contamination, while the clinicians should carefully interprete the result from blood culture in relation to clinical finding.

Keywords: hemocultures, Staphylococcus epidermidis, bloodstream infection rate, contamination rate, microbial sensitivity tests