Richard W Titball

Francisella tularensis is a potent pathogen and a possible bioterrorism agent. Little is known, however, to explain the molecular basis for its virulence and the distinct differences in virulence found between the four recognized subspecies, F. tularensis subsp. tularensis, F. tularensis subsp. mediasiatica, F. tularensis subsp. holarctica, and F. tularensis subsp. novicida. We developed a DNA microarray based on 1,832 clones from a shotgun library used for sequencing of the highly ...

We have determined the sequence of the gene cluster encoding the O antigen in Francisella novicida and compared it to the previously reported O-antigen cluster in Francisella tularensis subsp. tularensis. Immunization with purified lipopolysaccharide (LPS) from F. tularensis subsp. tularensis or F. novicida protected against challenge with Francisella tularensis subsp. holarctica and F. novicida, respectively. The LPS from F. tularensis subsp. tularensis did not confer protection against ...

The caf operon from Yersinia pestis encoding the structural subunit (caf1), the molecular chaperone (caf1M), the outer membrane anchor (caf1A), and the regulatory protein (caf1R) was cloned into Salmonella typhimurium SL3261 aroA. The recombinant Salmonella organisms were encapsulated when cultured at 37 degrees C but not when cultured at 28 degrees C. Oral inoculation of mice with the recombinant Salmonella induced predominantly an immunoglobulin G2a response to F1 antigen, and isolated ...

Yersinia pestis, the causative agent of plague, diverged from Yersinia pseudotuberculosis, an enteric pathogen, an estimated 1500-20,000 years ago. Genetic characterization of these closely related organisms represents a useful model to study the rapid emergence of bacterial pathogens that threaten mankind. To this end, we undertook genome-wide DNA microarray analysis of 22 strains of Y. pestis and 10 strains of Y. pseudotuberculosis of diverse origin. Eleven Y. pestis DNA loci were ...

Bubonic and pneumonic plague are caused by the bacterium Yersinia pestis. The V antigen of Y. pestis is a protective antigen against plague. In this study, an aroA attenuated strain of Salmonella enterica serovar Typhimurium (SL3261) has been used to deliver the Y. pestis V antigen as a candidate oral plague vaccine. SL3261 was transformed with the expression plasmid pTrc-LcrV, containing the lcrV gene encoding V antigen. Immunoblot analysis showed V antigen expression in SL3261 in vitro ...

Burkholderia pseudomallei is the causative agent of melioidosis, an often fatal infectious disease for which there is no vaccine. B. pseudomallei is listed as a tier 1 select agent, and as current therapeutic options are limited due to its natural resistance to most antibiotics, the development of new antimicrobial therapies is imperative. To identify drug targets and better understand the complex B. pseudomallei genome, we sought a genome-wide approach to identify lethal gene targets. ...

The Gram-negative bacterium Yersinia pestis is the causative agent of the systemic invasive infectious disease classically referred to as plague1, and has been responsible for three human pandemics: the Justinian plague (sixth to eighth centuries), the Black Death (fourteenth to nineteenth centuries) and modern plague (nineteenth century to the present day). The recent identification of strains resistant to multiple drugs2 and the potential use of Y. pestis as an agent of biological ...

BACKGROUND: Burkholderia pseudomallei is the causative agent of melioidosis, a tropical disease of humans with a variable and often fatal outcome. In murine models of infection, different strains exhibit varying degrees of virulence. In contrast, two related species, B. thailandensis and B. oklahomensis, are highly attenuated in mice. Our aim was to determine whether virulence in mice is reflected in macrophage or wax moth larvae (Galleria mellonella) infection models.

RESULTS: B. ...

V antigen of Yersinia pestis is a multifunctional protein that has been implicated as a protective antigen, a virulence factor, and a regulatory protein. A series of V-antigen truncates expressed as glutathione S-transferase (GST) fusion proteins (GST-V truncates) have been cloned and purified to support immunogenicity and functionality studies of V antigen. Immunization studies with GST-V truncates have identified two regions of V antigen that confer protection against Y. pestis 9B (a ...

The lack of novel antibiotics for more than a decade has placed increased pressure on existing therapies to combat the emergence of multidrug-resistant (MDR) bacterial pathogens. This study evaluated the Galleria mellonella insect model in determining the efficacy of available antibiotics against planktonic and biofilm infections of MDR Pseudomonas aeruginosa and Klebsiella pneumoniae strains in comparison with in vitro minimum inhibitory concentration (MIC) determination. In general, in ...

A gene cluster encoding enzymes involved in LPS O antigen biosynthesis was identified from the partial genome sequence of Francisella tularensis subsp. tularensis Schu S4. All of the genes within the cluster were assigned putative functions based on sequence similarity with genes from O antigen biosynthetic clusters from other bacteria. Ten pairs of overlapping primers were designed to amplify the O antigen biosynthetic cluster by PCR from nine strains of F. tularensis. Although the gene ...

Bacillus anthracis is the causative agent of anthrax, a disease that affects wildlife, livestock, and humans. Protection against anthrax is primarily afforded by immunity to the B. anthracis protective antigen (PA), particularly PA domains 4 and 1. To further the development of an orally delivered human vaccine for mass vaccination against anthrax, we produced Salmonella enterica serovar Typhimurium expressing full-length PA, PA domains 1 and 4, or PA domain 4 using codon-optimized PA ...

In this study, the protection afforded against aerosolized Yersinia pestis by injection of an alhydrogel-adsorbed sub-unit vaccine has been compared with that given by an existing killed whole cell vaccine licensed for human use. The sub-unit vaccine protected mice against exposure to > 10(4) colony-forming units (c.f.u.) of virulent plague organisms (100 LD50 doses), whereas the whole cell vaccine provided only 50% protection against 1.8 x 10(3) c.f.u. In sub-unit vaccinees, IgG to each ...

Melioidosis is a severe infectious disease of animals and humans caused by the Gram-negative intracellular pathogen Burkholderia pseudomallei. An Inv/Mxi-Spa-like type III protein secretion apparatus, encoded by the B. pseudomallei bsa locus, facilitates bacterial invasion of epithelial cells, escape from endocytic vesicles and intracellular survival. This study investigated the role of the Bsa type III secretion system in the pathogenesis of melioidosis in murine models. B. pseudomallei ...

To investigate Yersinia pathogenicity and the evolutionary divergence of the genus, the effect of pathogenic yersiniae on the model organism Caenorhabditis elegans was studied. Three strains of Yersinia pestis, including a strain lacking pMT1, caused blockage and death of C. elegans; one strain, lacking the haemin storage (hms) locus, caused no effect. Similarly, 15 strains of Yersinia enterocolitica caused no effect. Strains of Yersinia pseudotuberculosis showed different levels of ...