About

Kelsey Johnson is an Assistant Professor of Population and Public Health Sciences at the Keck School of Medicine of USC. Her research focuses on maternal and infant health, particularly examining the relationships between gestational diabetes, human milk composition, and infant growth and microbiome development. Her work explores how maternal genetics and physical activity influence human milk metabolites and how these factors impact infant adiposity, gut microbiome, and overall development. Johnson's contributions include investigating the mechanistic links between human milk variation and infant health outcomes, as well as the influence of maternal diet and health conditions on milk composition. Her research aims to deepen understanding of early-life nutritional and microbial factors that shape long-term health, contributing valuable insights to the fields of public health, nutrition, and pediatric development.

Research topics

• Gerontology
• Psychiatry
• Internal medicine
• Medicine
• Psychology
• Environmental health

Selected publications

• Quantification of Salmonella in Raw Poultry Using Droplet Digital PCR With a Whole Cell, Enrichment-free Approach

  Journal of Food Protection · 2025-03-25 · 1 citations

  articleOpen access

  • Pathotrak enables enrichment-free separation and concentration of microorganisms. • Pathotrak paired with ddPCR quantifies microorganisms in complex food matrices with accuracy. • ddPCR provides quantification without standard curves, minimizing PCR inhibition effects. • The protocol detects microorganisms at regulatory-relevant levels across food matrices. • Pathotrak and ddPCR recovery mirrors MPN, ensuring precise enumeration for food safety. Salmonella contamination in poultry remains a persistent public health challenge, despite ongoing regulatory efforts to reduce its presence. Traditional culture-based enrichment methods commonly employed for detecting Salmonella have inherent limitations, such as biases in bacterial growth and inaccurate quantification of initial contamination levels. This study introduces an enrichment-free approach for quantifying Salmonella in raw poultry, utilizing the Pathotrak system for bacterial separation and concentration, followed by Droplet Digital PCR (ddPCR) for absolute quantification. Our findings highlight that whole-cell preparations within ddPCR droplets yield significantly higher detection efficiency compared to extracted DNA, likely due to the reduced loss of genetic material during processing. The method was validated by correlating theoretical inoculation levels with ddPCR measurements, resulting in a strong linear relationship ( R 2 = 0.903) and a slope of 0.99, indicating high accuracy. Residuals from the regression model were normally distributed, confirming its validity. This platform offers a robust, rapid, and precise tool for detecting low levels of Salmonella in poultry products without enrichment, making it a more accurate and efficient approach to bacterial quantification in complex food matrices.

  PublisherDOI

• Multiplexed Detection of Salmonella, Escherichia coli, Campylobacter, and Listeria in Raw Poultry

  Foods · 2025-03-25 · 1 citations

  articleOpen access

  The detection of foodborne pathogens is a critical aspect of ensuring food safety. Traditional methods rely on time-intensive enrichment steps and pathogen-specific assays, extending testing timelines and limiting throughput. This study evaluates an enrichment-free, multiplexed pathogen detection workflow combining the Pathotrak system for bacterial separation and the Neogen Molecular Detection System (MDS) for detection. The workflow enables simultaneous detection of Salmonella, Escherichia coli O157, Listeria monocytogenes, Listeria spp., and Campylobacter in poultry samples, significantly reducing the time taken to screen samples requiring further evaluation. The system’s performance was assessed using inoculated chicken samples over a range of bacterial concentrations (102–108 CFU/mL). The MDS system demonstrated robust detection for most pathogens, with strong correlations between theoretical inoculation levels and MDS-calculated concentrations (R2 > 0.85 for all pathogens). However, detection variability was observed at lower concentrations for Salmonella and Listeria monocytogenes. The system maintained high sensitivity and specificity, achieving a Cohen’s Kappa coefficient for E. coli and Campylobacter. This study highlights the potential of enrichment-free, multiplex detection to streamline food safety testing by reducing the time to results, enhancing efficiency, and providing reliable pathogen quantification across multiple targets.

  PublisherOA PDFDOI

• A review of the American College of Surgeons accredited education institutes’ assessment practices for learners, faculty, and continuous program improvement

  Global Surgical Education - Journal of the Association for Surgical Education · 2023-04-19 · 3 citations

  reviewOpen access
  PublisherOA PDFDOI

• Trial of the MIND Diet for Prevention of Cognitive Decline in Older Persons

  New England Journal of Medicine · 2023 · 303 citations

  • Gerontology
  • Psychology
  • Medicine

  BACKGROUND: Findings from observational studies suggest that dietary patterns may offer protective benefits against cognitive decline, but data from clinical trials are limited. The Mediterranean-DASH Intervention for Neurodegenerative Delay, known as the MIND diet, is a hybrid of the Mediterranean diet and the DASH (Dietary Approaches to Stop Hypertension) diet, with modifications to include foods that have been putatively associated with a decreased risk of dementia. METHODS: We performed a two-site, randomized, controlled trial involving older adults without cognitive impairment but with a family history of dementia, a body-mass index (the weight in kilograms divided by the square of the height in meters) greater than 25, and a suboptimal diet, as determined by means of a 14-item questionnaire, to test the cognitive effects of the MIND diet with mild caloric restriction as compared with a control diet with mild caloric restriction. We assigned the participants in a 1:1 ratio to follow the intervention or the control diet for 3 years. All the participants received counseling regarding adherence to their assigned diet plus support to promote weight loss. The primary end point was the change from baseline in a global cognition score and four cognitive domain scores, all of which were derived from a 12-test battery. The raw scores from each test were converted to z scores, which were averaged across all tests to create the global cognition score and across component tests to create the four domain scores; higher scores indicate better cognitive performance. The secondary outcome was the change from baseline in magnetic resonance imaging (MRI)-derived measures of brain characteristics in a nonrandom sample of participants. RESULTS: A total of 1929 persons underwent screening, and 604 were enrolled; 301 were assigned to the MIND-diet group and 303 to the control-diet group. The trial was completed by 93.4% of the participants. From baseline to year 3, improvements in global cognition scores were observed in both groups, with increases of 0.205 standardized units in the MIND-diet group and 0.170 standardized units in the control-diet group (mean difference, 0.035 standardized units; 95% confidence interval, -0.022 to 0.092; P = 0.23). Changes in white-matter hyperintensities, hippocampal volumes, and total gray- and white-matter volumes on MRI were similar in the two groups. CONCLUSIONS: Among cognitively unimpaired participants with a family history of dementia, changes in cognition and brain MRI outcomes from baseline to year 3 did not differ significantly between those who followed the MIND diet and those who followed the control diet with mild caloric restriction. (Funded by the National Institute on Aging; ClinicalTrials.gov number, NCT02817074.).

  PublisherOA PDFDOI

• Impact of the COVID-19 pandemic on American College of Surgeons–Accredited Education Institutes & American Society of Anesthesiologists–Simulation Education Network: Opportunities for interdisciplinary collaboration

  Surgery · 2022-07-06

  articleOpen access
  PublisherOA PDFDOI

• Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) study: Rationale, design and baseline characteristics of a randomized control trial of the MIND diet on cognitive decline

  Contemporary Clinical Trials · 2021 · 141 citations

  • Medicine
  • Gerontology
  • Internal medicine
  PublisherOA PDFDOI

• High-Resolution Dynamic Pore Pressure Monitoring to Determine Hydraulic Parameters in a Multi-Layered Bedrock System for Improved Aquifer Vulnerability Assessment and Monitoring

  The Atrium (University of Guelph) · 2020-10-01 · 1 citations

  dissertationOpen access1st authorCorresponding

  Approximately 30% of Canadians rely on groundwater for their basic water needs. The City of Guelph is one of the largest cities in Canada to rely solely on a fractured rock dolostone aquifer for its drinking and fresh water supply. For this study, a vertical string of 21 pressure transducers was deployed behind a FLUTe liner in a borehole, within 250m of a municipal supply well in Guelph, Ontario, to record depth-discrete pore pressure transients over 60 days at 10s frequency. Regression deconvolution was used to determine the loading and pumping response functions using input variables including barometric pressure, Earth tides, river stage and pumping rates from 2 nearby municipal wells using distributed lags. Loading response functions determined over two time periods showed changing loading efficiency (LE) conditions relating to changing pumping or vadose zone conditions. Twelve hydrogeologic units were delineated, including four discontinuous aquitard units. An updated conceptual site model with lithostratigraphy was calibrated with the hydraulic data analysis providing hydraulic parameter estimates for LE, transmissivity and storativity in support of future 3D flow system numerical modelling.

  Publisher

• What are the Top Research Priorities in Surgical Simulation and How Can They Be Best Addressed? Results From a Multidisciplinary Consensus Conference

  Annals of Surgery · 2020-11-23 · 5 citations

  article

  OBJECTIVES: To define the top priorities in simulation-based surgical education where additional research would have the highest potential to advance the field and develop proposals that would address the identified research priorities. SUMMARY AND BACKGROUND DATA: Simulation has become integral part of surgical training but there are a number of outstanding questions that have slowed advances in this field. METHODS: The Delphi methodology was used to define the top priorities in simulation-based surgical education. A research summit was held with multiple stakeholders under the auspices of the American College of Surgeons Division of Education to develop proposals to address these priorities. RESULTS: Consensus was achieved after the first round of voting on the following 3 most important topics: (1) impact of simulation training on patient safety and outcomes, (2) the value proposition of simulation, and (3) the use of simulation for physician certification and credentialing. Knowledge gaps, challenges and opportunities, and research questions to address these topics were defined by summit participants. CONCLUSIONS: The top 3 priorities in surgical simulation research were defined and project outlines were developed for impactful projects on these topics. Successful completion of such projects is expected to advance the field of simulation-based surgical education.

  PublisherDOI

• Collection Development Policy, Digital Commons Institutional Repository, University of Nebraska–Lincoln Libraries, November 13, 2019

  Lincoln (University of Nebraska) · 2019-01-01

  article

  Purpose of the UNL Digital Commons Institutional Repository The UNL institutional repository (IR) comprises services that result in the stewardship and global online dissemination of content created and selected by UNL authors and affiliates. With the aim of contributing to the broader world of scholarship and facilitating discovery, the repository reflects the intellectual life of the institution.1 The IR drives a significant level of Web traffic to UNL. As such, the IR may serve as a promotional and marketing tool for authors, programs, and the university as a whole. Purpose of the Collection Development Policy This collection development policy is intended to provide guidance for content selection that anticipates and meets the needs of the communities of the University of Nebraska–Lincoln. It directly relates to the library's vision statement and defines the scope and standards that guide the services that generate the collection.

  Publisher

• Chlorophyll-a Detection for 317 Maine Freshwater Lakes Through the Use of Archived Data from LANDSAT Satellite Imagery, 23,000 in situ Samples, and Google Earth Engine

  AGUFM · 2018-12-01

  articleSenior author
  Publisher

Frequent coauthors

• Christina Chambers

  University of California, San Diego

  24 shared

• Robert J. Felix

  University of California, San Diego

  23 shared

• Gerald Briggs

  16 shared

• Beth Conover

  Nebraska Medical Center

  16 shared

• Ken Jones

  California State University, Fullerton

  16 shared

• Stephen R. Braddock

  Maternité Port Royal

  16 shared

• Susan Mach

  Utah Department of Health

  16 shared

• Jody Haun

  Great Lakes Research Group (United States)

  16 shared