Infection Control & Hospital Epidemiology (2018), 39, 972–979 doi:10.1017/ice.2018.138
Review
Wastewater drains: epidemiology and interventions in 23 carbapenem-resistant organism outbreaks
Philip C. Carling MD, FSHEA1,2 1Infectious Diseases Section, Steward Carney Hospital, Boston, Massachusetts and 2Boston University School of Medicine, Boston, Massachusetts
Abstract
For many years, patient-area wastewater drains (ie, sink and shower drains) have been considered a potential source of bacterial pathogens that can be transmitted to patients. Recently, evolving genomic epidemiology tools combined with new insights into the ecology of wastewater drain (WWD) biofilm have provided new perspectives on the clinical relevance and hospital-associated infection (HAI) transmission risks related to these fixtures. To further clarify the clinical relevance of WWD-associated pathogen transmission, reports of outbreaks attributed to WWDs were selected for review that (1) investigated the outbreak epidemiology of WWD-associated transmission of bacterial pathogens, (2) utilized advanced microbiologic methods to establish clonality of outbreak pathogens and/or resistance genes, or (3) described interventions implemented to mitigate transmission of the outbreak pathogens from WWDs. These reports were collated, compared, and analyzed, and the results are presented here.
(Received 17 January 2018; accepted 9 May 2018; electronically published June 28, 2018) Background
While the basic elements of healthcare-associated pathogen epi- demiology and acquisition are well recognized, new insights into the complexity of transmission events, particularly with respect to carbapenem-resistant organisms (CROs), have begun to evolve dramatically. The first recognition of and validation of trans- mission clusters of gram-negative pathogens occurred as a result of the recognition of new resistance patterns in Klebsiella pneu- moniae and Acinetobacter baumannii.1 Improved species-specific typing technologies and, recently, the rapidly escalating use of sequencing have greatly facilitated what is now recognized as genomic epidemiology. Although water tap and/or aerator Pseu- domonas outbreaks were recognized and remediated in the 1990s,1 only when Berrouane et al2 identified and corrected a whirlpool drain–associated Pseudomonas outbreak in 2000 did wastewater drain (WWD) systems begin to be evaluated as a potential source of environmental CRO transmission to patients. In 2003, Yomoda et al3 described the first reported outbreak associated with the transferrable bla(IMP) carbapenamase genes among Pseudomonas spp cultured from WWDs.3 Subsequently, 20 additional reports describing both the epidemiology and the mitigation initiatives were published; they serve as the basis for this review. All of these outbreaks were caused by CROs: Pseu- domonas spp (n=9), K. pneumoniae (n=3), K. oxytoca (n=3), Escherichia coli (n=3), multiple CROs (n=3), Acinetobacter (n=1), and Serratia (n=1).
Author for correspondence: Philip C. Carling, MD, Infectious Diseases Section,
Steward Carney Hospital, 2100 Dorchester Avenue, Boston, MA 02124. E-mail:
pcarling@comcast.net
Cite this article: Carling PC (2018). Wastewater drains: epidemiology and interventions in 23 carbapenem-resistant organism outbreaks. Infection Control & Hospital Epidemiology 2018, 39, 972–979. doi: 10.1017/ice.2018.138
© 2018 by The Society for Healthcare Epidemiology of America. All rights reserved. Methods
The PubMed database (1990–2018) was searched using multiple text terms: “healthcare drains” and “wastewater drains” as well as “sink drains” and “shower drains” individually and combined with the terms “biofilm” and “outbreaks.” All studies that met the fol- lowing inclusion criteria were analyzed and compared: (1) inves- tigated the clinical outbreak epidemiology of WWD-associated transmission of CROs, (2) utilized advancedmicrobiologicmethods to establish clonality of outbreak pathogens and/or resistance genes, or (3) described interventions implemented to mitigate transmis- sion of the outbreak pathogens from WWDs.
Results Demographic features
All 23WWD-associated outbreaks included in this review occurred in acute-care hospitals and involved CROs. Among them, 16 out- breaks (69%) occurred in Europe, 3 outbreaks (13%) occurred in the United States, 3 outbreaks (13%) occurred in Australia, and 1 (4%) occurred in Canada. Also, 22 outbreaks (95%) were associated with high-risk patient settings. Furthermore, 19 outbreaks (87%) were related to a single CRO: P. aeruginosa (n=9),3–5,11,15,17,19,21 K. pneumonia (n=3),6,7,12 E. coli (n=3),18,20,22 K. oxytoca (n=3),8,10,16 and a Serratia species (n=1)13 (Table 1). In addition, 4 outbreaks (17%) involved between 2 and 6 species of CROs that shared thesameresistancegeneorgenes.9,14,23,24 Of the 17 outbreaks reported since 2013, 6 (35%) were associated with metallo-β-lacta- mase–producing CROs: 5 occurred in Europe and 1 occurred in Australia.9,10,15,18,21,22 In the past 17 years, 8 reports have described WWD-associated outbreaks without evaluating mitigation inter- vention.25–32 In these studies, 1 or more CROs were identified as the outbreak strain (ObS). These outbreaks occurred in 8 intensive care
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