Increased environmental sample area and recovery ofClostridium difficilespores from hospital surfaces by quantitative PCR and enrichment culture

Abstract

AbstractObjectiveClostridium difficilespores play an important role in transmission and can survive in the environment for several months. Optimal methods for measuring environmentalC. difficileare unknown. We sought to determine whether increased sample surface area improved detection ofC. difficilefrom environmental samples.SettingSamples were collected from 12 patient rooms in a tertiary-care hospital in Toronto, Canada.MethodsSamples represented small surface-area and large surface-area floor and bedrail pairs from single-bed rooms of patients with low (without prior antibiotics), medium (with prior antibiotics), and high (C. difficileinfected) shedding risk. Presence ofC. difficilein samples was measured using quantitative polymerase chain reaction (qPCR) with targets on the 16S rRNA and toxin B genes and using enrichment culture.ResultsOf the 48 samples, 64·6% were positive by 16S qPCR (geometric mean, 13·8 spores); 39·6% were positive by toxin B qPCR (geometric mean, 1·9 spores); and 43·8% were positive by enrichment culture. By 16S qPCR, each 10-fold increase in sample surface area yielded 6·6 times (95% CI, 3·2–13) more spores. Floor surfaces yielded 27 times (95% CI, 4·9–181) more spores than bedrails, and rooms ofC. difficile–positive patients yielded 11 times (95% CI, 0·55–164) more spores than those of patients without prior antibiotics. Toxin B qPCR and enrichment culture returned analogous findings.ConclusionsClostridium difficilespores were identified in most floor and bedrail samples, and increased surface area improved detection. Future research aiming to understand the role of environmentalC. difficilein transmission should prefer samples with large surface areas.