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Natalia Blanco et al
Fig. 1. Main transmission pathways involved in hospital transmission of multidrug- resistant organisms (MDROs).
in hospitals has resulted in disagreements regarding the most appropriate infection prevention measures needed to prevent trans- mission of these organisms in healthcare settings. For example, this leads to large discussions about the pros and cons of contact precautions. This scoping review aims to fill this research gap by synthesiz-
ing the existing evidence on MDRO hospital transmission. We have summarized the best evidence on each of the 5 following potential transmission routes: (1) patient to HCW, (2) patient to environment, (3) HCW to patient, (4) environment to patient, and (5) environment to HCW (Fig. 1). Additionally, we have syn- thesized findings from high-quality manuscripts that demonstrate the overall contribution of patient-to-patient transmission in hos- pitals irrespective of the transmission routes.
Methods
We performed a scoping review, which is a widespread methodol- ogy to systematically search, select, and summarize existing evidence on a specific subject to identify research gaps.14,15 We chose this methodology instead of a traditional systematic review because it provided the flexibility to perform a general preliminary assessment of the existing literature on the complex and multifac- eted topic of transmission of MDROs in the hospital setting.
Study identification and selection
We performed 2 separate searches in PubMed, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL). The first search focused on MDRO transmission via the HCW or the environment to identify research studying specific transmis- sion pathways (patient toHCW, patient to environment,HCW to patient, environment to patient, or environment to HCW). We used the following search terms: multidrug-resistant organism AND healthcare personnel OR environment OR equipment AND disease transmission OR cross-transmission OR nosocomial transmission. The second search focused on overall patient-to- patient transmission regardless of whether the study specifically evaluated the transmission pathway. The following search terms were included: multidrug-resistant organism AND disease trans- mission OR cross-transmission OR nosocomial transmission OR patient-to-patient transmission. Both searches identified terms in the title, abstract, and keywords
fields.Amedical librarian devel- oped each search strategy. Only original research manuscripts written in English and pub-
lished during the last decade (2007–2017) were eligible for inclu- sion. Letters to the editor, guidelines, mathematical models, case studies, or outbreak investigations were excluded. Additionally, only research studies conducted in the acute-care setting among
adult populations focusing on the following MDROs were consid- ered: CRE,MRSA, VRE, and/or multidrug-resistant A. baumannii. Finally, to ensure that manuscripts satisfactorily demonstrated the transmission of the same multidrug-resistant strain across individuals, only manuscripts using modern molecular laboratory techniques such as whole-genome sequence (WGS) or pulsed-field gel electrophoresis (PFGE) were included. When studying the transmission pathways, manuscripts able to establish directionality of transmission (ie, patient to HCW vs HCW to patient) were preferred. One researcher (N.B.) screened all titles and abstracts for eli-
gibility. After abstract screening, the remaining papers were inde- pendently reviewed and rated by 3 researchers (N.B., A.D.H., and L.O.) using predefined objective criteria to identify the highest- quality manuscripts. The following main criteria used for manu- script evaluation were extracted: type of study design, sample size, and discriminatory power of themolecular technique used to dem- onstrate relatedness between strains. Disagreements were resolved by consensus. The best manuscripts from each search were sum- marized using a standardized template to synthesize the existing evidence on hospital transmission of MDROs. Additionally, the evidence level of consistency across each transmission route was categorized as either high, moderate, or low based on the level of agreement across studies.
Results Potential transmission routes
After searching 3 databases, 4,596 manuscripts were identified and one additional record was added by hand searching references of included articles. After removal of duplicates and elimination of articles based on title and abstract review, 41 full-text articles were reviewed. Finally, 12 articles were selected for inclusion in this scoping review (Fig. 2). These were the most common reasons for exclusion: (1) the study was not based in an acute-care setting; (2) the study did not include at least 1 of our selected MDROs; (3) the study took place during an epidemic or outbreak; (4) the study did not incorporate modern molecular techniques to assure same- strain transmission; (5) the article did not present original research; and (6) the type of manuscript/analysis was defined as part of the exclusion criteria (ie, letter to the editor, mathematical models, and case reports). Transmission from patient to HCW. The probable primary
source of the MDRO is the colonized or infected patient, and the patient may contaminate the HCW. Several high-quality papers have shown the transmission of MDROs from patients to HCWs, and in this review, we highlight 4 such prospective stud- ies (Table 1). All of these studies demonstrated transmission of the same strain from the patient toHCWhands, gloves, and/or gowns using PFGE.8,9,16,17 The main limitation of these studies is their ability to separate the effect of patient transmission to HCW from the effect of environmental transmission to HCW. However, the study published by Morgan et al in 2012 directly connected patient strains (instead of environmental strains) to the isolated strains in gowns and gloves in 82% of the analyzed cases.8 Insummary, based on the studies identified in our review, existing evidence demon- strating transmission from patient to HCW is highly consistent across available research even though variability in the amount of transmission was observed across microorganisms as expected. Transmission from patient to environment. In addition to trans-
mitting the MDRO to HCW, a colonized or infected patient may contaminate the surrounding hospital environment. This review
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