Multidrug-Resistant Organisms: Preventing Acquisition and Transmission

Multidrug-resistant organisms (MDRO) are a global problem, causing treatment challenges which result in worse health outcomes and high healthcare costs. As resistance to antibiotics continues to develop causing treatment failures, infection prevention strategies have become necessary. This dissertation offers research into discovering potential targets for intervention of MDRO acquisition through prevention of multiple MDRO colonization and infection and prevention of infection and transmission through the environment. The introduction for these topics will be covered in chapter one. In chapter two, we analyzed a four-year, prospective study to identify risk factors among hospitalized patients for co-colonization and coinfection (CCCI) with methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE), a predecessor to vancomycin-resistant S. aureus. Using conditional logistic regression, we identified admission from another healthcare facility as a risk factor when comparing CCCI patients to patients with MRSA only and patients without MRSA or VRE, indicating healthcare exposure increases the risk of CCCI. Molecular analysis indicated CCCI may be more likely to occur in patients colonized or infected with MRSA strains typically associated with hospital-associated infections. We recognized patients who may benefit from additional resources for infection prevention and control in the hospital to prevent acquisition of an emerging MDRO through multiple organism colonization or infection. MDRO environmental contamination facilitates MDRO transmission. In chapter three, we identified a hospitalized patient type colonized with MDRO more likely to contaminate their environment. Using latent class analysis, we categorized patients into two classes based on mechanical ventilation status, consciousness status at admission and requiring assistance with activities of daily living prior to admission. Low functional status patients were more likely to contaminate their environment. Infection prevention practices, such as hygiene assistance, enhanced environmental disinfection and contact precautions may contribute to reducing the burden of environmental contamination by these patients. Chapter four includes a surveillance study of environmental contamination in a child care center with the goal of guiding environmental cleaning and disinfection practices. We demonstrated the feasibility of longitudinal surveillance of a variety of fomites to detect overall contamination and the frequency of contamination with MDRO and viral pathogens. Water-associated sites were identified as harboring a higher bioburden and being contaminated more frequently with pathogens, demonstrating the potential of water to act as a reservoir for microorganisms and distribute them in the environment. We detected a higher bioburden on objects with irregular surfaces or which were cleaned less frequently. Child care providers should consider the ability to decontaminate a surface balanced against the development of children when including items in the classroom. Chapter five examines the knowledge added from this research and the public health implications related to our findings. Support for current infection prevention and control recommendations are addressed and additional strategies for interventions are considered. Potential future research directions informed by findings in this dissertation, including investigations into mechanisms of acquisition and transmission and potential interventions to interrupt these processes are discussed. In the appendix, I present a proposal for a future research project to develop a self-screening method for VRE. While this may have multiple applications, my goal is to use this in community-based studies, where VRE is prevalent but under-investigated. Better surveillance of VRE in the community will inform best practices for prevention of transmission and acquisition in this setting, while also guiding future research regarding VRE in community.PHDEpidemiological ScienceUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/168025/1/kchedid_1.pd

Targeting the Type II Secretion System: Development, Optimization, and Validation of a High-Throughput Screen for the Identification of Small Molecule Inhibitors

Nosocomial pathogens that develop multidrug resistance present an increasing problem for healthcare facilities. Due to its rapid rise in antibiotic resistance, Acinetobacter baumannii is one of the most concerning gram-negative species. A. baumannii typically infects immune compromised individuals resulting in a variety of outcomes, including pneumonia and bacteremia. Using a murine model for bacteremia, we have previously shown that the type II secretion system (T2SS) contributes to in vivo fitness of A. baumannii. Here, we provide support for a role of the T2SS in protecting A. baumannii from human complement as deletion of the T2SS gene gspD resulted in a 100-fold reduction in surviving cells when incubated with human serum. This effect was abrogated in the absence of Factor B, a component of the alternative pathway of complement activation, indicating that the T2SS protects A. baumannii against the alternative complement pathway. Because inactivation of the T2SS results in loss of secretion of multiple enzymes, reduced in vivo fitness, and increased sensitivity to human complement, the T2SS may be a suitable target for therapeutic intervention. Accordingly, we developed and optimized a whole-cell high-throughput screening (HTS) assay based on secreted lipase activity to identify small molecule inhibitors of the T2SS. We tested the reproducibility of our assay using a 6,400-compound library. With small variation within controls and a dynamic range between positive and negative controls, the assay had a z-factor of 0.65, establishing its suitability for HTS. Our screen identified the lipase inhibitors Orlistat and Ebelactone B demonstrating the specificity of the assay. To eliminate inhibitors of lipase activity and lipase expression, two counter assays were developed and optimized. By implementing these assays, all seven tricyclic antidepressants present in the library were found to be inhibitors of the lipase, highlighting the potential of identifying alternative targets for approved pharmaceuticals. Although no T2SS inhibitor was identified among the compounds that reduced lipase activity by ≥30%, our small proof-of-concept pilot study indicates that the HTS regimen is simple, reproducible, and specific and that it can be used to screen larger libraries for the identification of T2SS inhibitors that may be developed into novel A. baumannii therapeutics

Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients

International audienceThe aim of this study was to estimate the incidence of COVID-19 disease in the French national population of dialysis patients, their course of illness and to identify the risk factors associated with mortality. Our study included all patients on dialysis recorded in the French REIN Registry in April 2020. Clinical characteristics at last follow-up and the evolution of COVID-19 illness severity over time were recorded for diagnosed cases (either suspicious clinical symptoms, characteristic signs on the chest scan or a positive reverse transcription polymerase chain reaction) for SARS-CoV-2. A total of 1,621 infected patients were reported on the REIN registry from March 16th, 2020 to May 4th, 2020. Of these, 344 died. The prevalence of COVID-19 patients varied from less than 1% to 10% between regions. The probability of being a case was higher in males, patients with diabetes, those in need of assistance for transfer or treated at a self-care unit. Dialysis at home was associated with a lower probability of being infected as was being a smoker, a former smoker, having an active malignancy, or peripheral vascular disease. Mortality in diagnosed cases (21%) was associated with the same causes as in the general population. Higher age, hypoalbuminemia and the presence of an ischemic heart disease were statistically independently associated with a higher risk of death. Being treated at a selfcare unit was associated with a lower risk. Thus, our study showed a relatively low frequency of COVID-19 among dialysis patients contrary to what might have been assumed