Diagnostic Comparison of PCR, Chromogenic Agar and Culture for Vancomycin-Resistant Enterococci in Intensive Care Units

Comparison of Diagnostic Methods for VRE Detection 204

Abstract

Objective: This study aimed to compare the diagnostic performance and cost-effectiveness of classical culture, chromogenic agar, and the Smart-Cycle I-CORE real-time polymerase chain reaction (PCR) method for detecting vancomycin-resistant enterococci (VRE) in intensive care unit (ICU) patient and environmental samples.
Methods: In a prospective surveillance design conducted in adult medical, surgical, and general ICUs, perianal/rectal swab samples from patients hospitalized ≥48 hours and high-touch environmental surface samples were obtained. Each specimen was tested in parallel using classical culture, chromogenic agar, and real-time PCR targeting vanA/vanB. Sensitivity, specificity, positive and negative predictive values (PPV/NPV), turnaround time, and per-test costs were calculated.
Results: In patient samples, PCR, chromogenic agar, and culture achieved sensitivity/specificity of 100%/100%, 100%/80%, and 95.2%/86.4%, respectively. In environmental samples, PCR showed 100%/100%, chromogenic agar 100%/92%, and culture 94%/100%, respectively. PCR provided a markedly shorter time-to-result (~4 h), compared with chromogenic agar (~24 h) and classical culture (~48 h). vanA was the predominant genotype (≈82%), followed by vanB (≈18%). Although PCR was the most costly method, its rapid turnaround time contributed to earlier isolation decisions and to a reduction in environmental positivity rates.
Conclusion: Smart-Cycle I-CORE PCR offers the highest diagnostic accuracy and the fastest reporting among currently available surveillance methods, while chromogenic agar represents a reliable and cost-effective option. A two-step strategy—chromogenic agar for routine screening with PCR confirmation—balances accuracy, speed, and cost in ICU VRE surveillance.