Microbiologist — Division of Microbiology

Robert Wagner, Ph.D.
(870) 543-7121
NCTRResearch@fda.hhs.gov  

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 About  |  Publications  | Lab Members

Background

Dr. Robert Wagner worked in a clinical laboratory as a medical technologist while working to receive his Bachelor of Science from Eastern Illinois University. He then acquired a Master of Science in chemistry from Illinois State University. His education was supplemented by membership in The American Society of Clinical Pathologists and the American Chemical Society. He was awarded a Ph.D. in microbiology and immunology from the University of Missouri in 1989. He was a member of the American Society for Microbiology, with which he continues to be affiliated. He was awarded a U.S. Department of Agriculture National Needs Fellowship for that training and was honored at the American Academy of Science.  

After receiving his Ph.D., Dr. Wagner worked on the molecular genetics of human hypobetalipoproteinemia at the Lipid Research Center at Washington University Medical School. He was associated with the American Heart Association during his two-year tenure at Washington University.

Dr. Wagner worked at the University of Wisconsin Veterinary Medical School Pathobiology Division on the pathogenesis and host response to Listeria monocytogenes infections, where he was active in the American Society for Microbiology, the Society for Leukocyte Biology, and the American Association of Immunologists. In 1994, he moved to the University of Washington’s School of Medicine and studied host-parasite relationships with a eukaryotic pathogen, Candida albicans, and worked in collaboration with the Ross Products Division of Abbott Laboratories on probiotics in infant formulas. 

Dr. Wagner began his tenure at NCTR in 1997. By request of FDA’s Center for Veterinary Medicine (CVM) he characterized probiotic competitive-exclusion products. Dr. Wagner developed an in vitro assay of antimicrobial drug-residue effects on intestinal-microbiota colonization resistance. He presented at FDA’s Center for Food Safety and Applied Nutrition (CFSAN) Food Advisory Committee on Probiotics in September of 2000, which was an important meeting to define the role of FDA in regulating probiotic products. Research discussions with CFSAN and CVM led to a study in gnotobiotic mice of interactions between the human-intestinal microbiota and the pathogen Salmonella enterica, yielding an important discovery that the infection leads to immunosuppression of the mice. Dr. Wagner initiated a gnotobiotic research program at NCTR, which was essential to accomplish the Salmonella immunosuppression project. He was a co-principal investigator on a Cooperative Research and Development Agreements with the Pfizer Animal Health Company to study the effects of Ceftiofur and Ceftriaxone on the bovine intestinal microbiome. 

Dr. Wagner’s laboratory is collaborating with the FDA Office of Women’s Health to study effects of probiotic bacteria, phytoestrogens, and nanotechnology products on vaginal epithelial responses to Candida albicans. Dr. Wagner participated in FDA’s Live Microbial Ingredients Working Group and currently works with the Human Microbiota Working Group, where he maintains an interest in probiotic regulatory policy.  
 

Research Interests

Dr. Wagner’s research focus is on host defense against bacterial and fungal infections at mucosal interfaces. Recently, his research has expanded to study the effects of FDA-regulated products on mucosal infections. His laboratory is studying the mechanism of probiotic suppression of Salmonella enterica immunosuppression. In this study, changes in lymphocyte activation and traffic in mucosa-associated lymphoid tissues of mice orally infected with S. enterica with and without treatment with probiotic bacteria were evaluated by qRT-PCR and immunohistochemistry. Probiotic bacteria increased T- and B-lymphocyte activation and reduced apoptosis and inflammatory responses to S. enterica. The results of this study are consistent with prevention of S. enterica-induced clonal deletion of T-cells by the influence of probiotic bacteria in mucosal lymphoid tissues of mice.

His laboratory is investigating intestinal microbiome influences on epithelial and dendritic cell microtissue responses to Clostridium difficile infection, providing insight into the mechanisms of fecal microbiota transplantation. His research group developed a novel apparatus that provides oxygen to human cells and an anaerobic environment to the bacteria, and is generating human dendritic cells from induced pluripotent dendritic cells using growth factors and fluorescent activated cell sorting. The roles of representative strains of commensal bacteria in suppressing or enhancing C. difficile disease are being explored using quantitative real-time PCR measurements of mRNA concentrations and flow cytometric measurements of cell stress. The effects of FDA-regulated drugs like the Peroxisome Proliferator-Activated Receptor γ (PPARγ) agonist pioglitazone and proton pump inhibitor pentoprazole are being assessed in this study.  The results will help industry select better probiotic alternatives to fecal transplantation as therapies for C. difficile disease. 

Dr. Wagner’s laboratory is studying human vaginal-epithelial cell interactions with nanoparticles for intravaginal drug delivery. Nanoparticles consisting of polylactic acid-co-glycolic acid (PLGA)-polyethylene glycol (PEG) that could improve targeting of microbicidal drugs for sexually transmitted diseases by intravaginal inoculation in this study aggravate vaginal-epithelial cell proinflammatory responses to Candida albicans. The results show that mucous-penetrating nanoparticle drug-delivery vehicles cause intracellular damage to vaginal-epithelial cells by several mechanisms and that their use for intravaginal drug delivery may exacerbate inflammation in active yeast infections by increased inflammatory recruitment.

Dr. Wagner and his research team have begun a study of intravaginal drug-delivery nanoparticles effect on murine inflammation during vaginal candidiasis. Fluorescently labelled PLGA-PEG-Rho6G nanoparticles have been designed for intravaginal delivery to the mice. The effects of the nanoparticles on mice infected with C. albicans show increased markers of inflammation and cytotoxicity. The nanoparticles induce oxidative effects, disruption of intracellular metabolic responses, and DNA damage in vaginal epithelial tissues of the mice. This study will enhance their understanding of nanoparticle effects on candidiasis.

His laboratory is also investigating vaginal-microbiota disruption by silver nanoparticles in feminine hygiene products. A healthy, diverse vaginal microbiota — which may be adversely affected by contact with nanosilver — is essential for prevention of bacterial and fungal vaginoses and sexually transmitted diseases. A model vaginal microbiota in a vaginal-epithelial cell-culture model shows that silver nanowires found in some feminine hygiene products and mixed silver nanoparticles present in a homeopathic medicine product disrupt the composition of the vaginal microbiota as shown using conventional microbiological techniques and next-generation 16S ribosomal DNA sequencing. This work will provide an estimation of the impact of silver nanoparticles on the survival of these microbes relative to their capacity to maintain a protective level of colonization resistance in the vaginal environment. Dr. Wagner and his laboratory staff intend to continue researching the effects of existing and potential FDA-regulated products on the complex interactions of the human microbiome and mucosal diseases.
 

Professional Societies/National and International Groups

American Society for Microbiology
Member
2012 – 2015
 

Selected Publications

A Metallo-β-Lactamase is Responsible for the Degradation of Ceftiofur by the Bovine Intestinal Bacterium Bacillus Cereus P41.
Erickson B., Elkins C., Mullis L., Heinze T., Wagner R., and Cerniglia C. 
Veterinary Microbiology. 2014, 172 (3-4):499-504.

Probiotic Lactobacillus and Estrogen Effects on Vaginal Epithelial Gene Expression Responses to Candida Albicans.
Wagner R. and Johnson S. 
J Biomed Sci. 2012, 19:58-66.

Protection of Vaginal Epithelial Cells with Probiotic Lactobacilli and the Effect of Estrogen Against Infection by Candida Albicans.
Wagner R., Johnson S., and Tucker D.
Open J Med Microbiol. 2012, 2:54-64.

Bovine Intestinal Bacteria Inactivate and Degrade Ceftiofur and Ceftriaxone with Multiple β-Lactamases. 
Wagner R., Johnson S., Cerniglia C., and Erickson B.
Antimicrob Agents Chemother. 2011, 55(11):4990-4998.

Probiotic Bacteria are Antagonistic to Salmonella Enterica and Campylobacter Jejuni and Influence Host Lymphocyte Responses in Human Microbiota-Associated Immunodeficient and Immunocompetent Mice.
Wagner R., Johnson S., and Kurniasih-Rubin D. 
Mol Nutr Food Res. 2009, 53(3):377-388.

Vancomycin-Resistant Lactococcus Lactis Isolated from a Competitive Exclusion Product Can Transfer the vanA Gene to Staphylococus Aureus.
Wagner R., Kurniasih-Rubin D., and Johnson S.
Open Food Sci J. 2008, 2:72-76.

An In Vitro Model of Colonization Resistance by the Enteric Microbiota:  Effects of Antimicrobial Agents Used in Food-Producing Animals.
Wagner R., Johnson S., and Cerniglia C. 
Antimicrob Agents Chemother. 2008, 52(4):1230-1237.

Enhanced Production of Phospholipase C and Perfringolysin O (Alpha and Theta Toxins) in a Gatifloxacin-Resistant Strain of Clostridium perfringens.
Rafii F., Park M., Bryant A., Johnson S., and Wagner R.
Antimicrob Agents Chemother. 2008, 52(3):895-900.

Effects of Microbiota on GI Health: Gnotobiotic Research. 
Wagner R.
Adv Exper Med Biol. 2008, 635:41-56.

Efficacy and Food Safety Considerations of Poultry: Competitive Exclusion Products.
Wagner R.
Mol Nutr Food Res. 2006, 50(11):1061-1071.

Phenotypic and Genotypic Characterization of Competitive Exclusion Products for Use in Poultry.
Wagner R., Paine D., and Cerniglia C.
J Appl Microbiol. 2003, 94(6):1098-107.

Biotherapeutic Effects of Probiotic Bacteria on Candidiasis in Immunodeficient Mice.
Wagner R., Warner T., Pierson C., Farmer J., Roberts L., Dohnalek M., Hilty M., and Balish E. 
Infect Immun. 1997, 65:4165-4172.
J Food Protect. 2002, 65(5):746-51.

B Cell “Knockout” Mice are Resistant to Mucosal and Systemic Candidiasis of Endogenous Origin, but Susceptible to Experimental Systemic Candidiasis.
Wagner R., Vazquez-Torres A., Jones-Carson J., Warner T., and Balish E. 
J Infect Dis. 1996, 174(3):589-97.

Recombinant Interleukin-12 Enhances Resistance of Mice to Listeria Monocytogenes Infection.
Wagner R., Steinberg H., Brown J., and Czuprynski C. 
Microb Pathog. 1994, 17(3):175-86.
 

Lab Members

Contact information for all lab members:
(870) 543-7121
NCTRResearch@fda.hhs.gov

Shemedia J. Johnson, M.S.
Microbiologist

Taslima Taher Lina, Ph.D.
Postdoctoral Fellow