Infection Control & Hospital Epidemiology (2018), 39, 917–923 doi:10.1017/ice.2018.103
Original Article
Increased environmental sample area and recovery of Clostridium difficile spores from hospital surfaces by quantitative PCR and enrichment culture
Kevin Antoine Brown PhD1,4, Laura K. MacDougall PhD1, Kim Valenta PhD7, Andrew Simor MD2,3, Jennie Johnstone MD, PhD1,3, Samira Mubareka MD, PhD2,3, George Broukhanski PhD1, Gary Garber MD1,3,5, Allison
McGeer MD3,6 and Nick Daneman MD, MSc1,2,3 1Public Health Ontario, Toronto, Canada, 2Sunnybrook Health Sciences Center, Toronto, Canada, 3Department of Medicine, University of Toronto, Toronto,
Canada, 4Dalla Lana School of Public Health, University of Toronto, Toronto, Canada, 5Department of Medicine, University of Ottawa, Ottawa, Canada, 6Mt Sinai Healthcare System, Toronto, Canada and 7Faculty of Environmental Sciences, McGill University, Toronto, Canada
Abstract
Objective: Clostridium difficile spores play an important role in transmission and can survive in the environment for several months. Optimal methods for measuring environmental C. difficile are unknown. We sought to determine whether increased sample surface area improved detection of C. difficile from environmental samples. Setting: Samples were collected from 12 patient rooms in a tertiary-care hospital in Toronto, Canada. Methods: Samples 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. difficile infected) shedding risk. Presence of C. difficile in samples was measured using quantitative polymerase chain reaction (qPCR) with targets on the 16S rRNA and toxin B genes and using enrichment culture. Results: Of 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 of C. 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. Conclusions: Clostridium difficile spores were identified in most floor and bedrail samples, and increased surface area improved detection. Future research aiming to understand the role of environmental C. difficile in transmission should prefer samples with large surface areas.
(Received 24 January 2018; accepted 8 April 2018)
Clostridium difficile is a gram-positive, anaerobic, spore-forming bacterium; it is a leading cause of healthcare-associated infective diarrhea. Risk factors for the disease include previous hospitali- zations, advanced age, and the use of antibiotics.1–3 Clostridium difficile spores play an important role in disease transmission. Spores can persist in the environment for several months and are resistant to stresses such as heat, oxygen, and disinfectants.4,5 Clostridium difficile spores are thought to be ubiquitous in the hospital environment,6 and contaminated hospital surfaces may serve as an important reservoir for transmission.7 However, optimal and standardized sampling and laboratory methods for assessing density of environmental C. difficile are not
Author for correspondence: Kevin Antoine Brown, Public Health Ontario, 480
University Ave, #300, Toronto, ON M5G1V2, Canada. E-mail:
kevin.brown@
oahpp.ca or
kevin.brown@
utoronto.ca Cite this article: Brown KA, et al. (2018). Increased environmental sample area and
recovery of Clostridium difficile spores from hospital surfaces by quantitative PCR and enrichment culture. Infection Control & Hospital Epidemiology 2018, 39, 917–923. doi:10.1017/ice.2018.103
known. Increasing surface area may maximize the potential to capture spores and push C. difficile quantities over the detection limit of a given laboratory method, enabling more precise mea- surements,8,9 but it might also increase the concentration of inhibitors and reduce detection. Larger surface areas also require larger sampling devices, and sponges are preferred over swabs for sampling such areas due to their larger size.10,11 Other challenges include how to consistently measure average environmental burden across surface types (eg, bedrails, floors, and other surfaces), and whether culture or culture-independent methods yield more reliable quantitative measures of the density of environmental C. difficile. Bedrails represent one of the most frequently touched surfaces in the hospital environment.12 Floors, while not a high-touch environment, are often the most C. difficile- contaminated surfaces in hospitals; thus, they may play a role in transmission.13While culture techniquesmay bemost readily linked to potential transmission and infection, culture-independent tech- niquesmay nevertheless improve quantification of the existing spore burden and risk.8
© 2018 by The Society for Healthcare Epidemiology of America. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://
creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. All rights reserved.
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