Dr. Gireesh Rajashekara


Food Animal Health Research Program
OARDC Wooster, OH 44691
Phone: (330)-263-3745
Email: rajashekara@osu.edu

Biographical Information

  • University of Minnesota, Minnesota, USA Ph.D. 1999 Microbiology
  • University of Agricultural Sciences, India M.V.Sc. 1993 Microbiology
  • University of Agricultural Sciences, India B.V.Sc. 1990 Veterinary Medicine

Research Interests

Research in my laboratory is focused on:

Understanding survival mechanisms and pathogenesis of foodborne zoonotic pathogen, Campylobacter. We are investigating the contribution of chemoreceptors, polyphosphate (poly P) and Twin Arginine Translocation (TAT) system dependent proteins in C. jejuni stress responses and virulence mechanisms and identify C. jejuni components that are regulated by these systems, understand their role in C. jejuni colonization in food producing animals as well as C. jejuni induced disease pathogenesis using animal models, and use these information to develop novel antimicrobial strategies against Campylobacter in humans as well as in food animal reservoirs. Particularly, we are interested in targeting Campylobacter proteins critical for its survival and virulence through high throughput chemical screening and targeting surface proteins as subunit vaccines.

Elucidating molecular mechanisms of how gut microflora modulates gut permeability and intestinal homeostasis and its impact on pathogenesis of enteric pathogens. Particularly, we are looking at how different lactic acid bacteria modulate host cellular pathways using high throughput microarray analysis in a gnotobiotic pig model. Further we are interested in studying the interaction of different probiotic bacteria with enteric pathogens.

Visualizing in real-time the dynamics of in vivo colonization of bacterial pathogens using novel methodologies. We have applied bioluminescent imaging combined with transposon mutagenesis to gain greater insight into plant-phytopathogens as well as plant-foodborne pathogens interactions to (i) monitor infection over time (ii) identify sites of bacterial colonization, and (iii) study the dynamics of infection including patterns of growth and clearance of bacteria in specific tissues. Further, we are combining this sensitive, real-time assay with high throughput chemical screening to identify effective sanitization strategies to control foodborne human pathogens as well as phytopathogens.


  • Rajashekara, G., V. Kapur and K. V. Nagaraja. Application of recombinant fimbrial protein antigen for the diagnosis of Salmonella enteritidis infection in poultry. United States Patent # 6,495,334.
  • Rajashekara, G., V. Kapur and K. V. Nagaraja. Application of recombinant fimbrial protein antigen for the diagnosis of Salmonella enteritidis infection in poultry. International Patent # WO 98/03656.
  • Gireesh Rajashekara and Gary Splitter. Brucella melitensis mutants and methods. Patent publication # US2008-0107682-A1.
  • Miller, S. A., G. Rajashekara and X. Xu. Clavibacter Michiganensis Subsp. Michiganensis Miller, S. A., G. Rajashekara and X. Xu. Clavibacter Bioluminescent mutants and application. US8227186 B1.
  • Rajashekara, G., X. Xu, Miller, S. A. Fuchs, J., and Nislow, C. Small molecule modulators of Clavibacter michiganensis subsp. michiganensis as a means to control tomato bacterial canker. Invention Disclosure submitted, Reference Number: IDF481264

Selected Publications


  1. Kandasamy S, Chattha KS, Vlasova AN, Rajashekara G, Saif LJ. Lactobacilli and Bifidobacteria enhance mucosal B cell responses and differentially modulate systemic antibody responses to an oral human rotavirus vaccine in a neonatal gnotobiotic pig disease model. Gut Microbes. 2014 Sep 1:0. [Epub ahead of print] PMID: 25483333
  2. Kassem II, Splitter GA, Miller S, Rajashekara G. Let There Be Light! Bioluminescent Imaging to Study Bacterial Pathogenesis in Live Animals and Plants. Adv Biochem Eng Biotechnol. 2014 Nov 14. [Epub ahead of print] PMID: 25395174
  3. Kashoma IP, Kumar A, Sanad YM, Gebreyes W, Kazwala RR, Garabed R, Rajashekara G. Phenotypic and Genotypic Diversity of Thermophilic Campylobacter spp. in Commercial Turkey Flocks: A Longitudinal Study. Foodborne Pathog Dis. 2014 Nov;11(11):850-60. doi: 10.1089/fpd.2014.1794. Epub 2014 Sep 3. PMID:25184688
  4. Kumar A, Vlasova AN, Liu Z, Chattha KS, Kandasamy S, Esseili M, Zhang X, Rajashekara G, Saif LJ. (2014). In vivo gut transcriptome responses to Lactobacillus rhamnosus GG and Lactobacillus acidophilus in neonatal gnotobiotic piglets. Gut Microbes. Mar-Apr;5(2):152-64. PMID: 24637605
  5. Malde A, Gangaiah D, Chandrashekhar K, Pina-Mimbela R, Torrelles JB, Rajashekara G. (2014). Functional characterization of exopolyphosphatase/guanosine pentaphosphate phosphohydrolase (PPX/GPPA) of Campylobacter jejuni. Virulence. Feb 25;5(4). PMID: 24569519
  6. Kassem II, Khatri M, Sanad YM, Wolboldt M, Saif YM, Olson JW, Rajashekara G. (2014). The impairment of methylmenaquinol:fumarate reductase affects hydrogen peroxide susceptibility and accumulation in Campylobacter jejuni. Microbiologyopen. Feb 7. doi: 10.1002/mbo3.158. PMID: 24515965


  1. Vlasova AN, Chattha KS, Kandasamy S, Liu Z, Esseili M, Shao L, Rajashekara G, Saif LJ. (2013). Lactobacilli and Bifidobacteria promote immune homeostasis by modulating innate immune responses to human rotavirus in neonatal gnotobiotic pigs. PLoS One. Oct 2;8(10):e76962. PMCID: PMC3788735; PMID: 24098572
  2. Chattha KS, Vlasova AN, Kandasamy S, Rajashekara G, Saif LJ. (2013). Divergent immunomodulating effects of probiotics on T cell responses to oral attenuated human rotavirus vaccine and virulent human rotavirus infection in a neonatal gnotobiotic piglet disease model. J Immunol. Sep 1;191(5):2446-56. PMID: 23918983.
  3. Kassem II, Chandrashekhar K, Rajashekara G. (2013). Of energy and survival incognito: A relationship between viable but non-culturable cells (VBNC) formation and inorganic polyphosphate and formate metabolism in Campylobacter jejuni. Frontiers in Microbiology. Vol 4, No. 00183, PMID: 23847606; PMCID: PMC3705167
  4. Sanad YM, Closs G Jr, Kumar A, LeJeune JT, Rajashekara G. (2013). Molecular Epidemiology and Public Health Relevance of Campylobacter Isolated from Dairy Cattle and European Starlings in Ohio, USA. Foodborne Pathogens and Disease. Mar;10(3):229-36. doi: 10.1089/fpd.2012.1293. Epub 2012 Dec 21. PMID: 23259503. Dec 21. [Epub ahead of print]. PMID: 23259503
  5. Kassem II, Chandrashekhar K, Rajashekara G. Of energy and survival incognito: a relationship between viable but non-culturable cells formation and inorganic polyphosphate and formate metabolism in Campylobacter jejuni. Front Microbiol. 2013 Jul 9;4:183. doi: 10.3389/fmicb.2013.00183. eCollection 2013. PMID: 23847606

Other Publications

  1. Xu X, Rajashekara G, Paul PA, Miller SA. (2012). Colonization of Tomato Seedlings by Bioluminescent Clavibacter michiganensis subsp. michiganensis under Different Humidity Regimes. Phytopathology: Feb;102(2):177-84. PMID: 21936661
  2. Drozd M, Gangaiah D, Liu Z, Rajashekara G. (2011). Contribution of PhoX to Twin Arginine Translocation mediated Campylobacter jejuni function and resilience to Environmental Stresses. PLoS One;6(10):e26336. Epub 2011 Oct 20. PMID: 22028859; PMCID:PMC3197622
  3. Sanad YM, Kassem II, Abley M, Gebreyes W, LeJeune JT, Rajashekara G. (2011). Genotypic and Phenotypic Properties of Beef Cattle-Associated Campylobacter and their Implications to Public Health in the USA. PLoS One: 6(10):e25778. PMID: 22046247; PMCID: PMC3198382
  4. Kassem II, Zhang Q, Rajashekara G. (2011). The twin arginine translocation (Tat) system : Contributions to the pathobiology of Campylobacter jejuni. Future Microbiol. Nov;6(11):1315-27. Review. PMID:22082291
  5. Kassem II, Rajashekara G. (2011). An ancient molecule in a recalcitrant pathogen: the contributions of Inorganic polyphosphate (Poly-P) to the pathogenesis and stress responses of Campylobacter jejuni. Future Microbiol. Oct;6:1117-20. PMID: 22004028
  6. Gangaiah D, Liu Z, Arcos J, Kassem II, Sanad Y, Torrelles JB, Rajashekara G. (2010). Polyphosphate Kinase 2: A Novel Determinant of Stress Responses and Pathogenesis in C. jejuni. PLoS One, PMID: 20808906; PMCID:PMC2923150
  7. Xu X, Miller SA, Baysal-Gurel F, Gartemann KH, Eichenlaub R, Rajashekara G. (2010). Bioluminescent imaging of Clavibacter michiganensis subsp. michiganensis infection of tomato seeds and plants. Appl Environ MicrobiolPMID: 20400561; PMCID:PMC2893490
  8. Gangaiah D, Kassem II, Liu Z, Rajashekara G. (2009). Importance of polyphosphate kinase 1 for C. jejuni viable-but-nonculturable cell formation, natural transformation, and antimicrobial resistance. Appl Environ MicrobiolPMID:19837830; PMCID:PMC2794102
  9. Swartz TE, Tseng TS, Frederickson MA, Paris G, Comerci DJ, Rajashekara G, Kim JG, Mudgett MB, Splitter GA, Ugalde RA, Goldbaum FA, Briggs WR, Bogomolni RA. (2007). Blue-Light–Activated HistidineKinases:Two-Component Sensors In Bacteria. Science. 317:1090-3. PMID: 17717187.
  10. Rajashekara, G. Glover, D.A., Krepps, M., and Splitter, G.A. (2005). Temporal analysis of pathogenic events in virulent and avirulent Brucella melitensis infections. Cellular Microbiology, 7:1459-73. PMID: 16153245