About

Martin Wiedmann is the Gellert Family Professor in Food Safety at Cornell University, with a focus on developing and communicating scientific knowledge to prevent and control foodborne and zoonotic diseases caused by bacteria, as well as microbial food spoilage. His academic program emphasizes a comprehensive and interdisciplinary farm-to-table approach to food safety and quality, integrating microbiology, microbial genetics, population genetics, molecular biology, genomics, evolution, and modeling. Wiedmann's research aims to better understand the pathogenesis, ecology, evolution, and transmission of bacterial foodborne and zoonotic diseases, with particular attention to pathogens such as Listeria monocytogenes and Salmonella, which cause significant human and animal health issues. He serves as co-director of the New York State Integrated Food Safety Center of Excellence and collaborates across disciplines to study the ecology of infectious diseases, including bacterial adaptation and virulence gene expression under varying environmental conditions. His outreach efforts focus on food safety and dairy microbiology, supporting programs that promote the production of safe, high-quality dairy products and providing training and applied research for producers and processors. Wiedmann's teaching philosophy emphasizes active learning, critical thinking, lifelong learning skills, and current, relevant content for students.

Research topics

• Biology
• Food science
• Ecology
• Genetics
• Computer Science
• Computational biology
• Microbiology
• Engineering
• Biotechnology
• Environmental science
• Mathematics
• Zoology
• Machine Learning
• Biochemical engineering
• Medicine
• Anatomy
• Operations management
• Botany
• Molecular biology
• Risk analysis (engineering)
• Evolutionary biology
• Business
• Statistics
• Environmental health

Selected publications

• Dynamic pricing to reduce retail dairy shrink: Evidence from lab and grocery store experiments

  SSRN Electronic Journal · 2026-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Correction: Risk assessment of Escherichia coli O157:H7 along the farm-to-fork fresh-cut romaine lettuce supply chain

  Scientific Reports · 2025-08-06

  erratumOpen access
  PublisherOA PDFDOI

• A fluid milk spoilage simulation framework reveals the need for spoilage intervention strategies that account for frequency of bacterial postpasteurization contamination

  Journal of Dairy Science · 2025-07-15 · 2 citations

  articleOpen access

  <h2>ABSTRACT</h2> Postpasteurization contamination (PPC) with gram-negative bacteria and the growth of spore-forming bacteria are major causes of fluid milk spoilage, typically leading to sensory defects when bacterial concentrations exceed 6 log₁₀ cfu/mL. Existing models focus on individual spoilage pathways, limiting their ability to capture the complexity of milk spoilage. To address this, we developed a simulation framework that simultaneously models the growth of both types of bacteria in high-temperature short-time pasteurized milk along a supply chain. Dairy processing plants were categorized into 3 groups based on shelf life of historical fluid milk: long, medium, and short shelf-life plants. We assumed varying initial PPC frequencies for each category, with ranges of 0% to 33% for long, 34% to 66% for medium, and 67% to 100% for short shelf-life plants. Shelf life, defined as when 25% of milk containers exceeded 6 log₁₀ cfu/mL, was predicted as 25, 12, and 8 d for long, medium, and short shelf-life plants, respectively. Our predictions aligned with observed bacterial growth in commercial milk stored at 6°C, with the percentage of milk containers exceeding 6 log₁₀ cfu/mL on d 14 falling within the fifth to 95th percentiles of simulated values. Sensitivity analysis identified key parameters influencing bacterial concentrations at shelf life d 7, 14, and 21 for long, medium, and short shelf-life plants, respectively, guiding intervention strategies. What-if scenario analysis revealed that effective intervention strategies to extend shelf life vary by plant categories. While interventions targeting spore-forming bacteria, such as microfiltration, bactofugation, and improved home storage conditions, extended the shelf life for long shelf-life milk by 3 to 5 d, PPC reduction extended shelf life by 5 and 4 d in medium and short shelf-life plants, respectively. This simulation framework provides a comprehensive spoilage prediction tool to support data-driven decision making for fluid milk processors.

  PublisherOA PDFDOI

• A Critical Review of Parameters Relevant for Shiga Toxin-producing Escherichia coli and Listeria monocytogenes Risk Assessments of Leafy Greens

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

  reviewOpen access

  In the past decade, several quantitative models and risk assessments for Shiga toxin-producing Escherichia coli (STEC) and Listeria monocytogenes have been developed to guide the management of these pathogens in fresh produce. However, there is a need to collect and critically review the parameters used to guide their potential reuse in future risk assessments. This review (i) identifies 11 and 7 recently published quantitative models and risk assessments for STEC and L. monocytogenes, respectively, in leafy greens, (ii) summarizes parameters, and (iii) reviews the underlying data sources or mathematical formulas used. A total of 70 unique key parameters (55 and 25 for STEC and L. monocytogenes, respectively, 10 shared) were extracted from the reviewed models across five supply chain stages, including: Preharvest, Harvest, Processing, Presentation to Consumer (Retail or Foodservice Locations), and Consumer Handling. Primary growth, secondary growth, and dose-response equations and parameters for STEC and L. monocytogenes were also extracted. Additional literature reviews were performed if (i) certain key parameters were based on a single or a few data sources or (ii) key parameters were identified in a supply chain stage for one pathogen, but missing from the other. The critical summaries of parameters presented here (i) provide a resource for future risk assessments, (ii) help define future data collection needs, and (iii) represent a starting point for similar reviews focusing on other produce commodities and pathogens.

  PublisherDOI

• Integration of mathematical modeling and economics approaches to evaluate strategies for control of Salmonella Dublin in a heifer-raising operation

  PLoS ONE · 2025-10-16 · 1 citations

  articleOpen accessCorresponding

  Salmonella Dublin infections in heifer-raising operations (HROs) cause animal health and economic losses for these operations and represent a pathogen source for dairy farms obtaining replacement heifers from HROs. To improve control of S. Dublin, we (i) developed a mathematical model of S. Dublin transmission on a HRO, (ii) evaluated the vaccine effectiveness and cleaning improvements for controlling the infection, and (iii) evaluated the influence of infection and control strategies on the HRO's operating income. We developed a modified Susceptible-Infected-Recovered-Susceptible model of S. Dublin spread in a batch-stocking HRO post-introduction of an index case, with stochasticity introduced through Monte Carlo simulations. Epidemiological outcomes (S. Dublin-induced deaths and abortions during raising and S. Dublin carriers and asymptomatic infections among raised replacement heifers) and operating income per 100-head raised on a HRO over a 2-year simulation were compared between control scenarios. We validated our model against S. Dublin infection data in cattle. Partial rank correlation coefficient analysis and classification trees were used to determine parameter influence on model outcomes. Our model predicts a median of 37 carriers and 92 asymptomatic infections among raised replacement heifers out of 2,330 heifers that departed the operation by the end of the 2-year simulation period, suggesting a relevant role of HROs in spreading S. Dublin. Increasing barn floor cleaning frequency (to a maximum of 12x per day) meaningfully reduced the S. Dublin epidemiological outcomes and improved the HRO's operating income. Depending on the cost of cleaning, the median operating income increased between 1.2% to 10.6% in the first year when cleaning 12x per day compared to baseline (cleaning 1x per week). In most cost scenarios, predictions do not support using a vaccine that solely reduces mortality, even when paired with stringent cleaning measures. The developed model is expected to aid efforts to control S. Dublin in HROs.

  PublisherDOI

• Diverse spore-forming bacterial populations in US organic raw milk are driven by climate region

  Journal of Dairy Science · 2025-03-03 · 1 citations

  articleOpen access

  Spore-forming bacteria pose significant challenges to the dairy industry, as they are present at high levels in the natural environment and can cause finished product spoilage. To improve organic raw milk quality and minimize spoilage caused by spore-forming bacteria, we used a farm-to-table approach, by assessing the levels and diversity of various spore types through longitudinal studies of United States (US) organic dairy supplies, including (1) raw milk from 100 organic dairy farms, (2) raw milk intended for organic cheese production from 5 processing plants, (3) pasteurized milk from 5 processing plants, and (iv) dairy powders from 2 processing plants. Based on a total of 4,194 isolates characterized by either rpoB or 16S rRNA gene sequencing, Bacillus spp. dominated the aerobic spore-formers isolated from farm raw milk, pasteurized milk, and powders. Nonmetric multidimensional scaling revealed that aerobic spore-former populations in organic farm raw milk differ significantly between climate zones at genus, species, and allelic type levels. The anaerobic/facultative anaerobic spore-formers isolated from farm and cheese raw milk samples represented the orders Clostridiales and Bacillales. Evaluation of the gas produced by anaerobic/facultative anaerobic spore-forming bacteria isolates showed that gas production varied significantly between Clostridiales clades, and 1 Bacillales clade produced gas amounts that were not significantly different from most Clostridiales clades. Overall, our data indicate (1) a substantial diversity of aerobic and anaerobic spore-formers in US organic dairy supplies with predominant genera and species similar between organic and conventional dairy supplies as previously described; (2) both anaerobic and facultative anaerobic spore-formers found in organic raw milk produce gas; and (3) climate may affect aerobic spore-former diversity in farm raw milk.

  PublisherOA PDFDOI

• Phylogeny and divergence of the 100 most common Salmonella serovars available in the NCBI Pathogen Detection database

  Frontiers in Microbiology · 2025-06-13 · 6 citations

  articleOpen access

  Despite the emergence of whole genome sequencing (WGS) for Salmonella characterization, serotype assignment remains important as it allows identification of Salmonella subgroups that differ in distribution, virulence, and ecology. However, it has been shown that multiple divergent lineages of the same Salmonella serovar may have evolved independently multiple times and may present distinct epidemiological characteristics. Previous studies that aimed to identify the phylogeny of certain Salmonella serovars often used isolates from specific geographical locations or outbreaks and a small number of isolates to infer the phylogeny. To address these limitations and to advance the understanding of Salmonella ’s evolutionary patterns, we (i) identified the phylogenetic grouping (i.e., mono-, para-, or polyphyly) of the 100 most common Salmonella serovars analyzing 63,204 genomes available in the NCBI Pathogen Detection database, (ii) identified, for each polyphyletic serovar, the lineages that contain the majority of genomes, and (iii) inferred the antigen divergence between the five most common serovars (i.e., Salmonella Enteritidis, Typhimurium, Newport, I 4,[5],12:i:-, and Infantis) and their respective closely-related serovars. Among the 100 most common Salmonella serovars analyzed, 19 serovars are monophyletic, nine are paraphyletic, and 72 are polyphyletic. In 47 of the 72 polyphyletic serovars, one lineage contains more than 90% of the serovar’s confirmed genomes. Antigen divergence results suggest that serovars Typhimurium and I 4,[5],12:i:- (often referred to as monophasic Typhimurium) have emerged independently of each other multiple times, except for the major I 4,[5],12:i:- lineage, which emerged from the major Typhimurium lineage. Furthermore, divergence in Salmonella serovars appears to primarily occur through modifications in the H1 antigen. Hence, this study shows that (i) a much larger number of serovars than previously known are polyphyletic; (ii) serovars previously known to be polyphyletic contain more lineages than previously known; and (iii) many serovars include lineages that only have a few isolates with a given serovar. Our data suggests that, in the age of genomics, molecular serotyping should be combined with other phylogenetically informative approaches to not just assign a serovar but to also indicate the serovar lineage for polyphyletic and paraphyletic serovars.

  PublisherOA PDFDOI

• Risk assessment of Escherichia coli O157:H7 along the farm-to-fork fresh-cut romaine lettuce supply chain

  Scientific Reports · 2025-05-20 · 1 citations

  articleOpen access

  Outbreaks of Escherichia coli O157:H7 (ECO157) in romaine lettuce remain an ongoing public health concern. Quantitative microbial risk assessment (QMRA) models are key tools for identifying control measures to mitigate foodborne diseases. Here, we introduce a comprehensive QMRA framework along the farm-to-fork fresh-cut romaine lettuce chain, including a novel preharvest difference equation model, to predict annual ECO157 illness cases in the United States and evaluate control strategies. We demonstrated the importance of managing irrigation-related contamination at preharvest to control illness cases. Wildlife intrusions pose lower health risk, followed by runoffs and biological soil amendments of animal origin. When preharvest contamination persists and combines with time-temperature abuses at postharvest, the predicted ECO157 illness cases rise considerably. We showed a broad range of interventions targeting both preharvest and postharvest stages can effectively improve the microbial safety of fresh-cut romaine. The comprehensive practices and interventions explored in this study will aid decision-makers in establishing/enhancing food safety best management practices.

  PublisherOA PDFDOI

• Raw milk from individual teats with an optimal teat-end score has lower spore levels compared with teats with a suboptimal teat-end score

  JDS Communications · 2025-09-17

  articleOpen access

  Udder health in dairy cows is routinely monitored (for example, through determination of SCC) to help identify and control mastitis and other infectious diseases. Another parameter used to both assess udder health and milking machine performance is the teat-end condition, typically assessed at the herd level using a 4-point scoring system. Recently, the teat-end score has been suggested as a factor associated with the levels of bacterial spores in raw milk. Spores of cold-tolerant sporeforming bacteria present in raw milk can survive pasteurization and contribute to the spoilage of fluid milk. Therefore, the objective of this study was to determine whether the condition of individual teat-ends (specifically, optimal versus suboptimal teat-end scores) affects the spore levels in raw milk obtained from these teats. A total of 102 raw milk samples were collected from 102 individual teats from cows on a single dairy farm, and tested for mesophilic spores, with 51 samples each from teats scored as either 1 (optimal) or 4 (suboptimal). A significantly lower mesophilic spore count was found in the raw milk samples collected from teats with a teat-end score of 1 compared with samples collected from teats with score of 4. The observed difference in mesophilic spore counts suggests that maintaining optimal teat-end condition through good udder health and milking machine management may help reduce spore levels in raw milk. Although the observed difference in mesophilic spore counts is expected to result in minimal improvement of fluid milk shelf-life and other quality parameters, interventions targeting teat-end status or farm management practices that aim to improve the same can still be an important incremental contributor to the overall improvement of these parameters as part of a comprehensive, multipronged approach to raw milk quality management.

  PublisherOA PDFDOI

• Farm-to-consumer quantitative microbial risk assessment model for <i>Listeria monocytogenes</i> on fresh-cut cantaloupe

  medRxiv · 2025-03-03

  preprintOpen access

  ABSTRACT Cantaloupe contamination with the foodborne pathogen Listeria monocytogenes (LM) may occur along the supply chain. We developed a quantitative microbial risk assessment (QMRA) model for LM on cantaloupe along the fresh-cut supply chain and evaluated potential risk reduction strategies. The developed model starts at harvest and includes conditions during transportation from field to intermediate facility (packinghouse or cooling facility), handling at the intermediate facility, transportation to the fresh-cut facility, storage pre-processing at the fresh-cut facility, processing and handling at the fresh-cut facility, as well as conditions during distribution, retail, transportation to home, and home storage. The model was simulated to (i) provide an estimate of LM concentration in a single serving (134 g) and (ii) estimate annual illnesses and deaths in the United States attributed to LM contaminated fresh-cut cantaloupe. The baseline model predicted the median risk of listeriosis per serving in general and susceptible populations was 1.4 × 10 −12 and 6.4 × 10 −11 , respectively. The median (5 th , 95 th percentiles) predicted number of illnesses and deaths annually attributed to fresh-cut cantaloupe were 0 (0, 1070) and 0 (0, 264), respectively. Time and temperature conditions post-packaging, and the initial number of LM at harvest had the greatest impacts on LM per contaminated serving and the number of annual illnesses; the initial LM levels at harvest and cross-contamination parameters at the fresh-cut facility had the greatest impacts on prevalence of contaminated servings. Assessment of interventions demonstrated that reducing temperature and/or time conditions post-packaging can be an effective risk reduction strategy. Overall, the developed tool estimates the risk associated with the consumption of LM contaminated fresh-cut cantaloupe and facilitates the identification and assessment of potential risk reduction strategies across the supply chain.

  PublisherOA PDFDOI

Recent grants

• NIH Grant R01HL060889

  NIH · $994k · 2004

• NIH Grant R01GM063259

  NIH · $1.2M · 2006

• NIH Grant R01GM050920

  NIH · $620k · 1999

Frequent coauthors

• Kathryn J. Boor

  129 shared

• Renato H. Orsi

  Cornell University

  94 shared

• Yrjo T. Gröhn

  89 shared

• Renata Ivanek

  New York State College of Veterinary Medicine

  73 shared

• N.H. Martin

  Indiana University Bloomington

  66 shared

• Lorin D. Warnick

  New York State College of Veterinary Medicine

  65 shared

• Laura M. Carroll

  Science for Life Laboratory

  63 shared

• Kevin J. Cummings

  Cornell University

  57 shared

Education

• Ph.D., Food Science

  Cornell University

  1996

• M.S., Food Science

  Cornell University

  1993

• B.S., Animal Science

  Cornell University

  1991

Awards & honors

• Fellow 2018 American Association for the Advancement of Scie…
• International Dairy Food Association (IDFA) Food Safety Lead…
• Fellow 2014 American Academy of Microbiology
• Fellow 2013 Institute of Food Technologist’s (IFT)
• International Academy of Food Science and Technology Divisio…