Betsy J Bricker

Animal and Plant Health Inspection Service, Buzzards Bay, Massachusetts, United States

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Publications (47)

  • Source
    Krishna K Gopaul · Jessica Sells · Betsy J Bricker · [...] · Adrian M Whatmore
    [Show abstract] [Hide abstract] ABSTRACT: The reliable differentiation of live Brucella vaccine strains from field isolates is an important element in brucellosis control programs. We describe the design, validation, and implementation of a novel single nucleotide polymorphism (SNP)-based typing platform that offers a rapid, reliable, and robust tool to achieve this with improved diagnostic accuracy compared to existing molecular tests. Furthermore, the assays described are designed such that they supplement, and can be run as an intrinsic part of, a previously described assay identifying Brucella isolates to the species level (K. K. Gopaul, C. J. Smith, M. S. Koylass, and A. M. Whatmore, BMC Microbiol. 8:86), giving a comprehensive molecular typing platform.
    Full-text Article · Feb 2010 · Journal of clinical microbiology
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    Albano Beja-Pereira · Betsy Bricker · Shanyuan Chen · [...] · Gordon Luikart
    [Show abstract] [Hide abstract] ABSTRACT: Identifying the source of infectious disease outbreaks is difficult, especially for pathogens that infect multiple wildlife species. Brucella spp. are among the most problematic zoonotic agents worldwide, and they are notoriously difficult to detect and identify. We genotyped 10 variable number of tandem repeat (VNTR) DNA loci in 56 Brucella abortus isolates from bison (Bos bison), elk (Cervus elaphus), and cattle (Bos taurus) to test the wildlife species most likely to be the origin of recent outbreaks of brucellosis in cattle in the Greater Yellowstone Area. Isolates from cattle and elk were nearly identical but highly divergent from bison isolates. These data suggest elk, not bison, are the reservoir species of origin for these cattle infections. This study illustrates the potential power of VNTR genotyping to assess the origin of disease outbreaks, which are increasing worldwide following habitat fragmentation, climate change, and expansion of human and livestock populations.
    Full-text Article · Oct 2009 · Journal of wildlife diseases
  • Chapter: Brucella
    [Show abstract] [Hide abstract] ABSTRACT: Brucellosis affects millions of animals and humans world-wide; in humans, over 500,000 new cases are reported annually. Although some vaccines are available for its prevention in animals, none exist for humans. The causative agent is the facultative intracellular bacterial pathogen belonging to the genus Brucella and is transmitted from animals to humans; infected animals experience abortion and humans undulant fever. Brucella spp. belong to the order Rhizobiales within the class alpha-Proteobacteria. This places them in a group of bacteria noted for their abilities to live in soil (e.g. Ochrobactrum) or form close associations with their host and result in either a disease (e.g. phytopathogenic Agrobacterium) or non-disease state (symbiotic Rhizobium). The scientists contributing to the chapter have a vast array of experience in studying this intracellular bacterial pathogen. The topics covered include disease history, vaccines and zoonotic implications, taxonomy, diagnostic and population dynamics, comparative and functional genomics, and host pathogen interactions related to the Brucella spp. In all, the chapter is a comprehensive look at the Brucella and the means by which we are trying to minimize the negative impacts it has on the animal kingdom.
    Chapter · Nov 2008
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    [Show abstract] [Hide abstract] ABSTRACT: We demonstrate that the "HOOF-Print" assay provides high power to discriminate among Brucella isolates collected oil a small spatial scale (within Portugal). Additionally, we illustrate how haplotype identification using non-random association among markers allows resolution of B. melitensis biovars (1 and 3). We recommend that future studies use haplotype identification when analyzing multilocus Population genetic data to help discriminate among microbial isolates such as Brucella. (c) 2008 Elsevier B.V. All rights reserved.
    Full-text Article · Nov 2008 · Infection Genetics and Evolution
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    Full-text Article · Oct 2008 · Infection Genetics and Evolution
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    Dataset: Table S4
    [Show abstract] [Hide abstract] ABSTRACT: List of genes identified to be different between attenuated strain S19 genome and the virulent strains, 9–941 and 2308 (0.09 MB XLS)
    Full-text Dataset · May 2008
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    Dataset: Table S1
    [Show abstract] [Hide abstract] ABSTRACT: Functional assignment of the ORFs of Brucella abortus Strain S19 using BLASTP searches against the protein datasets (0.54 MB XLS)
    Full-text Dataset · May 2008
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    Dataset: Table S2
    [Show abstract] [Hide abstract] ABSTRACT: Single Nucleotide Polymorphisms (SNPs) identified between S19 genome and 9–941 genome (0.20 MB XLS)
    Full-text Dataset · May 2008
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    Dataset: Table S3
    [Show abstract] [Hide abstract] ABSTRACT: Pair-wise and reciprocal comparisons between the genes and the genomes of the strains S19, 9–941 and 2308 (1.29 MB XLS)
    Full-text Dataset · May 2008
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    [Show abstract] [Hide abstract] ABSTRACT: The Brucella abortus strain S19, a spontaneously attenuated strain, has been used as a vaccine strain in vaccination of cattle against brucellosis for six decades. Despite many studies, the physiological and molecular mechanisms causing the attenuation are not known. We have applied pyrosequencing technology together with conventional sequencing to rapidly and comprehensively determine the complete genome sequence of the attenuated Brucella abortus vaccine strain S19. The main goal of this study is to identify candidate virulence genes by systematic comparative analysis of the attenuated strain with the published genome sequences of two virulent and closely related strains of B. abortus, 9-941 and 2308. The two S19 chromosomes are 2,122,487 and 1,161,449 bp in length. A total of 3062 genes were identified and annotated. Pairwise and reciprocal genome comparisons resulted in a total of 263 genes that were non-identical between the S19 genome and any of the two virulent strains. Amongst these, 45 genes were consistently different between the attenuated strain and the two virulent strains but were identical amongst the virulent strains, which included only two of the 236 genes that have been implicated as virulence factors in literature. The functional analyses of the differences have revealed a total of 24 genes that may be associated with the loss of virulence in S19. Of particular relevance are four genes with more than 60 bp consistent difference in S19 compared to both the virulent strains, which, in the virulent strains, encode an outer membrane protein and three proteins involved in erythritol uptake or metabolism.
    Full-text Article · Feb 2008 · PLoS ONE
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    [Show abstract] [Hide abstract] ABSTRACT: Eighty feral swine were trapped from a herd that had been documented to be seropositive for Brucella and which had been used for Brucella abortus RB51 vaccine trials on a 7,100-hectare tract of land in South Carolina. The animals were euthanized and complete necropsies were performed. Samples were taken for histopathology, Brucella culture, and Brucella serology. Brucella was cultured from 62 (77.5%) animals. Brucella suis was isolated from 55 animals (68.8%), and all isolates were biovar 1. Brucella abortus was isolated from 28 animals (35.0%), and isolates included field strain biovar 1 (21 animals; 26.3%), vaccine strain Brucella abortus S19 (8 animals, 10.0%), and vaccine strain Brucella abortus RB51 (6 animals, 7.5%). Males were significantly more likely to be culture positive than females (92.9% vs. 60.6%). Thirty-nine animals (48.8%) were seropositive. Males also had a significantly higher seropositivity rate than females (61.9% vs. 34.2%). The relative sensitivity rates were significantly higher for the standard tube test (44.6%) and fluorescence polarization assay (42.6%) than the card agglutination test (13.1%). Lesions consistent with Brucella infection were commonly found in the animals surveyed and included inflammatory lesions of the lymph nodes, liver, kidney, and male reproductive organs, which ranged from lymphoplasmacytic to pyogranulomatous with necrosis. This is the first report of an apparent enzootic Brucella abortus infection in a feral swine herd suggesting that feral swine may serve as a reservoir of infection for Brucella abortus as well as Brucella suis for domestic livestock.
    Full-text Article · Jun 2007 · Journal of veterinary diagnostic investigation: official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc
  • William C Stoffregen · Steven C Olsen · Betsy J Bricker
    [Show abstract] [Hide abstract] ABSTRACT: To determine the immunogenicity and efficacy of Brucella abortus strain RB51 (SRB51) as a vaccine in domestic pigs. Sixty-eight 6-week-old crossbred domestic pigs and twenty-four 4-month-old gilts. In experiment 1, pigs were vaccinated IM (n = 51) with 2 x 10(10) CFUs of SRB51 or sham inoculated (17). Periodic blood samples were obtained to perform blood cultures, serologic evaluations, and cell-mediated immunity assays. Necropsies were performed at selected times between weeks 1 and 23 after vaccination to determine vaccine clearance. In experiment 2, gilts were similarly vaccinated (n = 18) or sham inoculated (8) and similar samples were obtained after vaccination. Gilts were bred and challenged conjunctivally with 5.0 x 10(7) CFUs of virulent Brucella suis strain 3B. Necropsies were performed on gilts and on fetuses or neonates after abortion or parturition, respectively. Bacterial cultures and serologic evaluations were performed on samples obtained at necropsy to determine vaccine efficacy. Humoral and cell-mediated immune responses did not differ between vaccinates and controls. After vaccination, SRB51 was not isolated from blood cultures of either group and was isolated from lymphoid tissues of 3 pigs at 2 weeks (n = 2) and 4 weeks (1) after vaccination. No differences were found in isolation of B suis or in seroconversion between vaccinated and control gilts and between their neonates or aborted fetuses. Parenteral vaccination with SRB51 does not induce humoral or cell-mediated immune responses. Vaccination with SRB51 did not protect gilts or their neonates and fetuses from virulent challenge with B suis.
    Article · Nov 2006 · American Journal of Veterinary Research
  • Betsy J Bricker · Darla R Ewalt
    [Show abstract] [Hide abstract] ABSTRACT: A critical component of limiting bacterial disease outbreaks is the tracing of the infection to the index source, which can be facilitated by using a highly discriminating bacterial identification system that will reliably identify genetically related bacterial populations. For pathogenic bacteria with highly conserved genomes, such as the zoonotic pathogen Brucella, finding distinguishing markers or traits for strain identification is challenging. This chapter describes a relatively new procedure for identifying Brucella strains. The procedure, which is called "HOOF prints" (hypervariable octameic oligonucleotide fingerprints), is based on high levels of polymorphism observed at several genomic loci in the Brucella genomes that contain small tandemly repeated deoxyribonucleic sequences. The technique described is designed for medium- to high-throughput analyses. However, the method described can be modified to characterize fewer samples.
    Article · Feb 2006 · Methods in Molecular Biology
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    Betsy J Bricker · Darla R Ewalt
    [Show abstract] [Hide abstract] ABSTRACT: Cross-tabulation of allelic distribution within the variable HOOF-Print loci by geographic region. Statistical data from each of the six most variable loci are presented in cross-tabulations displaying the distribution of alleles between the eastern and western regions of the US.
    Full-text Dataset · Jun 2005
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    Betsy J Bricker · Darla R Ewalt
    [Show abstract] [Hide abstract] ABSTRACT: Brucella strains and HOOF-Print genotypes. List of all of the bacterial isolates used in this study, including the biovar designation of the isolate, the location of the infected herd, the year of isolation, and the HOOF-Print genotype.
    Full-text Dataset · Jun 2005
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    Shirley M Halling · Brooke D Peterson-Burch · Betsy J Bricker · [...] · Steven C Olsen
    [Show abstract] [Hide abstract] ABSTRACT: Brucellosis is a worldwide disease of humans and livestock that is caused by a number of very closely related classical Brucella species in the alpha-2 subdivision of the Proteobacteria. We report the complete genome sequence of Brucella abortus field isolate 9-941 and compare it to those of Brucella suis 1330 and Brucella melitensis 16 M. The genomes of these Brucella species are strikingly similar, with nearly identical genetic content and gene organization. However, a number of insertion-deletion events and several polymorphic regions encoding putative outer membrane proteins were identified among the genomes. Several fragments previously identified as unique to either B. suis or B. melitensis were present in the B. abortus genome. Even though several fragments were shared between only B. abortus and B. suis, B. abortus shared more fragments and had fewer nucleotide polymorphisms with B. melitensis than B. suis. The complete genomic sequence of B. abortus provides an important resource for further investigations into determinants of the pathogenicity and virulence phenotypes of these bacteria.
    Full-text Article · May 2005 · Journal of Bacteriology
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    Betsy J Bricker · Darla R Ewalt
    [Show abstract] [Hide abstract] ABSTRACT: A fundamental question that arises during epidemiological investigations of bacterial disease outbreaks is whether the outbreak strain is genetically related to a proposed index strain. Highly discriminating genetic markers for characterizing bacterial strains can help in clarifying the genetic relationships among strains. Under the auspices of the European Society of Clinical Microbiology and Infectious Diseases, the European Study Group for Epidemiological Markers (ESGEM) established guidelines for evaluating the performance of typing systems based of a number of criteria. Recently, HOOF-Print genotype analysis, a new method for typing Brucella abortus strains based on hypervariability at eight tandem repeat loci, was described. This paper evaluates the HOOF-Print assay by four of the criteria set out by the ESGEM: typeability, reproducibility, power of discrimination, and concordance with other typing methods. The HOOF-Print Assay was evaluated with a test population composed of 97 unrelated field isolates and 6 common laboratory strains of B. abortus. Both typeability and reproducibility of the assay were excellent. Allele diversity and frequency varied widely among the eight loci, ranging from 1 to 13 alleles. The power of discrimination, measured by the Hunter-Gaston discrimination index (HGDI), varied by locus ranging from 0 to 0.89, where a maximal value of 1.0 indicates discrimination of all strains. The HGDI values calculated for subgroups sorted by biovar were similar to the values determined for the whole population. None of the individual loci achieved the recommended HGDI threshold of 0.95, but the HGDI of the composite profiles was 0.99 (93 unique genotypes from 97 field strains evaluated), well above the recommended threshold. By comparison, the HGDI value for biovar typing was 0.61 in a test population biased with disproportionate numbers of the less common biovars. Cluster analysis based on HOOF-Print genotypes assembled the strains into hierarchical groups with no apparent association with the time or location of strain isolation. Likewise, these hierarchical groups were not homogeneous with regard to biotype. In one extreme case, two field isolates with identical fingerprints were identified as different biovars by conventional methods. The main purpose of this study was to assess the ability of HOOF-Print genotyping to discriminate unrelated field strains of B. abortus, and whether the assay met established requirements for bacterial strain typing methods. The discriminatory power of the assay was remarkable, considering the genetic homogeneity found among species within the genus. The assay met or exceeded all of the recommended levels for the performance criteria of typeability, reproducibility, and power of discrimination, however some inconsistencies with conventional biovar typing were observed. Nevertheless, the results indicate that with cautious interpretation, multilocus genotyping of polymorphic tandem repeats by HOOF-Print analysis could be a valuable complement to routine epidemiological investigations into localized B. abortus outbreaks.
    Full-text Article · Feb 2005 · BMC Microbiology
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    Betsy J Bricker · Darla R Ewalt · Shirley M Halling
    [Show abstract] [Hide abstract] ABSTRACT: Currently, there are very few tools available for subtyping Brucella isolates for epidemiological trace-back. Subtyping is difficult because of the genetic homogeneity within the genus. Sequencing of the genomes from three Brucella species has facilitated the search for DNA sequence variability. Recently, hypervariability among short tandem repeat sequences has been exploited for strain-typing of several bacterial pathogens. An eight-base pair tandem repeat sequence was discovered in nine genomic loci of the B. abortus genome. Eight loci were hypervariable among the three Brucella species. A PCR-based method was developed to identify the number of repeat units (alleles) at each locus, generating strain-specific fingerprints. None of the loci exhibited species- or biovar-specific alleles. Sometimes, a species or biovar contained a specific allele at one or more loci, but the allele also occurred in other species or biovars. The technique successfully differentiated the type strains for all Brucella species and biovars, among unrelated B. abortus biovar 1 field isolates in cattle, and among B. abortus strains isolated from bison and elk. Isolates from the same herd or from short-term in vitro passage exhibited little or no variability in fingerprint pattern. Sometimes, isolates from an animal would have multiple alleles at a locus, possibly from mixed infections in enzootic areas, residual disease from incomplete depopulation of an infected herd or molecular evolution within the strain. Therefore, a mixed population or a pool of colonies from each animal and/or tissue was tested. This paper describes a new method for fingerprinting Brucella isolates based on multi-locus characterization of a variable number, eight-base pair, tandem repeat. We have named this technique "HOOF-Prints" for Hypervariable Octameric Oligonucleotide Finger-Prints. The technique is highly discriminatory among Brucella species, among previously characterized Brucella strains, and among unrelated field isolates that could not be differentiated by classical methods. The method is rapid and the results are reproducible. HOOF-Printing will be most useful as a follow-up test after identification by established methods since we did not find species-specific or biovar-specific alleles. Nonetheless, this technology provides a significant advancement in brucellosis epidemiology, and consequently, will help to eliminate this disease worldwide.
    Full-text Article · Aug 2003 · BMC Microbiology
  • Betsy J Bricker · Darla R Ewalt · Steven C Olsen · Allen E Jensen
    [Show abstract] [Hide abstract] ABSTRACT: In a blind test, 344 samples representing 80 bacterial isolates were analyzed by the Brucella abortus species-specific polymerase chain reaction (BaSS PCR) assay for the identification and discrimination of B. abortus field strains (wild-type biovars 1, 2, and 4) from 1) B. abortus vaccine strains, 2) other Brucella species, and 3) non-Brucella bacteria. Identical samples were tested in 2 laboratories. Half the samples were fully viable, and half were bacteria that had been killed by methanol fixation. The results in 1 laboratory correctly identified 100% of the samples, resulting in a predictive value of 100% for all categories and 100% sensitivity and specificity under the prescribed conditions. The second laboratory misidentified 31 samples, resulting in a range of 66.7-100% sensitivity, 93.2-99.7% specificity, and 77.3-98.2% predictive values depending on the category. There was no significant difference in viable versus fixed bacteria for either laboratory. Subsequent review of the protocol indicated that contamination was the likely cause of 26 of the 31 erroneous identifications. The results show that the BaSS PCR assay has the potential to be a very reliable screening tool for B. abortus identification. However, the data also provide a cautionary reminder of the importance of preventing contamination in diagnostic PCR.
    Article · Aug 2003 · Journal of veterinary diagnostic investigation: official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc
  • BJ Bricker · DR Ewalt · SC Olsen · AE Jensen
    [Show abstract] [Hide abstract] ABSTRACT: In a blind test, 344 samples representing 80 bacterial isolates were analyzed by the Brucella abortus species-specific polymerase chain reaction (BaSS PCR) assay for the identification and discrimination of B. abortus field strains (wild-type biovars 1, 2, and 4) from 1) B. abortus vaccine strains, 2) other Brucella species, and 3) non-Brucella bacteria. Identical samples were tested in 2 laboratories. Half the samples were fully viable, and half were bacteria that had been killed by methanol fixation. The results in 1 laboratory correctly identified 100% of the samples, resulting in a predictive value of 100% for all categories and 100% sensitivity and specificity under the prescribed conditions. The second laboratory misidentified 31 samples, resulting in a range of 66.7-100% sensitivity, 93.2-99.7% specificity, and 77.3-98.2% predictive values depending on the category. There was no significant difference in viable versus fixed bacteria for either laboratory. Subsequent review of the protocol indicated that contamination was the likely cause of 26 of the 31 erroneous identifications. The results show that the BaSS PCR assay has the potential to be a very reliable screening tool for B. abortus identification. However, the data also provide a cautionary reminder of the importance of preventing contamination in diagnostic PCR.
    Article · Jul 2003 · Journal of veterinary diagnostic investigation: official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc

Publication Stats

2k Citations

Institutions

  • 2000-2007
    • Animal and Plant Health Inspection Service
      Buzzards Bay, Massachusetts, United States
  • 2006
    • United States Department of Agriculture
      • Agricultural Research Service (ARS)
      Washington, D. C., DC, United States
  • 2003
    • Agricultural Research Service
      Kerrville, Texas, United States