Chitrita "Chobi" DebRoy, MPhil, PhD

Research:

Sequencing and analyzing O antigen gene clusters of E. coli

E. coli are classified on the basis of O antigens that are lipopolysaccharides present on the outer surface of the bacteria. O-antigens are important virulent factors that are targets of both immune system and bacteriophages. Its specificity is very important for adaptation as its variation plays an important role in evasion of the host defenses. The designation of E. coli serotypes, comprising of O and H antigens, is of great importance in epidemiological studies, in tracing the source of the outbreaks of gastrointestinal or other illness, or for linking the source to the infection. Conventionally O antigens are determined by agglutination reactions using antisera raised in rabbits against the 174 different O serogroups. We have now sequenced O antigen gene clusters and developed PCR assays of more than 20 pathogenic O groups. This research will lead to the development of molecular diagnostics where all O-serogroups of E. coli can be detected rapidly.

Extraintestinal Pathogenic E. coli

E. coli can cause intestinal as well as extraintestinal infections. We have, for the first time, shown that extraintestinal pathogenic E. coli (ExPEC) can cause pneumonia in dogs, cats and horses. We have also shown that many of these ExPEC strains are related to strains that cause urinary tract infection in humans.

Antibiotic resistance in E. coli

The emergence and dissemination of antibiotic resistance in bacterial pathogens is a serious emerging problem world wide. We are trying to elucidate the mechanism by which microorganisms acquire new genes as a result of inter-species (horizontal) transfer of antimicrobial resistance determinants. A potential important factor in the development of antimicrobial resistance stems from animal husbandry practices, in which antimicrobial agents not only are used for treating and preventing animal diseases, but are also administered at sub therapeutic levels to promote faster growth and to improve efficiency of feed conversion into meat. This routine practice may be the driving force in accelerating the emergence of antibiotic resistant bacteria that are subsequently transferred from animals to humans through the food chain, including meat products and fresh produce. Studies on antimicrobial resistance pattern and modes of dissemination in pathogenic strains of E. coli isolated from animals are being conducted in our laboratory.

Diagnostics:

E. coli Reference Center is one of the largest repositories for E. coli isolates and a major diagnostic laboratory in North America. Serotyping and molecular diagnostics of E. coli are routinely performed. The presence of more than twenty five virulence attributes of E. coli is determined by PCR to ascertain the pathogenicity of the bacteria that are isolated from humans, animals, food, water and the environment. The characteristics of each isolate are recorded in the database and that can be retrieved easily.

Publications:(2005-2008)

Fratamico P, DebRoy C, and Liu Y. 2008. The DNA Sequence of the Escherichia coli O22 O Antigen Gene Cluster and Detection of Pathogenic Strains Belonging to E. coli Serogroups O22 and O91 by Multiplex PCR Assays Targeting Virulence Genes and Genes in the Respective O-Antigen Gene Clusters. Food Anal. Methods. (Online First)

DebRoy C, Roberts E, Jayarao B, and Brooks J. 2008. Extraintestinal Pathogenic E. coli (ExPEC) Induced Bronchopneumonia in a Horse. J.. Vet. Diagn. Invest. 20: 661-664

Liu Y, Fratamico P, DebRoy C, Bumbaugh A, and Allen J. 2008. DNA sequencing and identification of serogroup-specific genes in the Escherichia coli O118 O antigen gene cluster and demonstration of antigenic diversity but only minor variation in DNA sequence of the O antigen clusters of E. coli O118 and O151. Food-borne Pathogen Dis 5: 449-457.

Dickinson CE, Gould DH, Davidson AH, Avery PR., Legare ME, Hyatt DR, and DebRoy C. 2008. Hemolytic-uremic syndrome in a postpartum mare concurrent with encephalopathy in the neonatal foal. J. Vet Diagn. Invest. 20:239-242.

Houser BA, Donaldson SC, Padtee R, Sawant AA, DebRoy C, and. Jayarao BM. 2008. Assessment of Phenotypic and Genotypic Diversity of Escherichia coli Shed by Healthy Lactating Dairy Cattle. J. Food-borne Pathogen Dis 5:41-51.

Johnson JR, Johnston B, Clabots CR, Kuskowski MA, Roberts E, and DebRoy C. 2008. Virulence genotypes and phylogenetic background of Escherichia coli serogroup O6 isolates from humans, dogs and cats. J. Clin. Microbiol. 46:417-422.

Sura R, Van Kruiningen HJ, DebRoy C, Hinckley LS, Greenberg KJ, Gordon Z, and French RA. 2007. Extraintestinal pathogenic E.coli (ExPEC) induced acute necrotizing pneumonia in cats. Zoonoses Public Health 54:307-313.

Liu Y, DebRoy C, and Fratamico P. 2007. Sequencing and analysis of the Escherichia coli serogroup O117, O126, and O146 O antigen gene clusters and development of PCR assays targeting serogroup O117-, O126-, and O146- specific DNA sequences. Mol. Cell. Probes 21:295-302.

Waswa J, Irudayaraj J, and DebRoy C. 2007 Direct detection of E.coli O157:H7 in selected food systems by a surface plasmon resonance biosensor. LWT 40:187-192

Kariyawasam S, Johnson TJ, DebRoy C, and Nolan LK. 2006. Occurrence of pathogenicity island I (APEC-O1) genes among Escherichia coli implicated in avian colibacillosis. Avian Dis. 50:405-10.

DebRoy C, and Roberts E. 2006. Screening petting zoo animals for the presence of potentially pathogenic Escherichia coli. J. Vet. Diag. Invest. 18: 597-600.

Shelton DR, Karns JS, Higgins JA, Van Kessel JAS, Perdue ML, Belt KT, Russell-Anelli J, and DebRoy C. 2006. Impact of microbial diversity on rapid detection of enterohemorrhagic Escherichia coli in surface waters. FEMS Letters 261:95-101.

Donaldson SC, Straley BA, Hegde NV, Sawant AA, DebRoy C, and Jayarao BM. 2006. Molecular epidemiology of ceftiofur resistant Escherichia coli. Appl. Env. Microbiol. 72:3940-8.

Palaniappan RUM, Zhang Y, Chiu D, Torres A, DebRoy C, Whittam TS,and Chang Y. 2006. Differentiation of Escherichia coli pathotypes by oligonucleotide spotted array. J. Clin. Microbiol. 44: 1495-1501.

Waswa J, DebRoy C, and Irudayaraj J. 2006. Rapid detection of Salmonella enteritidis and Escherichia coli using the BiacoreTM Surface Plasmon Resonance biosensor. J. Food Process Engineering 29: 373-385.

Schmilovitch Z, Mizrach A, Alchanatis V, Kritzman G, Korotic R, Irudayaraj J, and DebRoy C. 2005. Detection of bacteria with low resolution Raman spectroscopy. Trans. ASAE. 48: 1843-1850.

Gupta M, Irudayaraj J, DebRoy C, Schmilovitch Z, and Mizrach A. 2005. Differentiation of food pathogens using FTIR and artificial neural network. Trans. ASAE. 48: 1-4.

Singh R, Schroeder CM, Meng JH, White DG, McDermott PF, Wagner DD, Yang H, Simjee S, DebRoy C, Walker RD, and Zhao S. 2005. Identification of antimicrobial resistance and class I integrons in shiga toxin-producing Escherichia coli recovered from humans and food animals. J. Antimicrobial Chemo. 56: 216-219.

DebRoy C, Fratamico PM, Roberts E, Davis MA, and Liu Y. 2005. PCR Assays for detection and identification of Escherichia coli O45 and O55 serogroups targeting the wzx and wzy genes in the O antigen gene clusters. Appl. Env. Microbiol. 71: 4919-4924.

Fratamico PM, DebRoy C, Strobaugh TP, and Chen CY. 2005. DNA sequence of the Escherichia coli O103 O antigen gene cluster and detection of enterohemorrhagic E.coli O103 by PCR amplification of wzx and wzy genes. Can. J. Microbiol. 51: 515-522.

Breitschwerdt E, DebRoy C, Mexas A, Brown T, and Remick A. 2005. Isolation of necrotoxigenic Escherichia coli from a dog with hemorrhagic pneumonia. JAVMA 226: 2016-2019.

Ramachandani M, Manges AR, DebRoy C, Johnson JR, and Riley LW. 2005. Possible animal origin of human multidrug-resistant uropathogenic Escherichia coli. Clin. Infect. Dis. 40: 251-257.