Nada R.A.,Us Naval Medical Research Unit No 3 |
Shaheen H.I.,Us Naval Medical Research Unit No 3 |
Khalil S.B.,Us Naval Medical Research Unit No 3 |
Mansour A.,Us Naval Medical Research Unit No 3 |
And 7 more authors.
Journal of Clinical Microbiology | Year: 2011
Enterotoxigenic Escherichia coli (ETEC) is recognized to be a common cause of acute watery diarrhea in children from developing countries. Colonization factors (CFAs) have been identified predominantly in ETEC isolates secreting heat-stable enterotoxin (ST) or cosecreting ST with a heat-labile toxin (LT). We hypothesized that LT-only-secreting ETEC produces unique colonization factors not previously described in ST and LTSTsecreting ETEC. A set of degenerate primers based on nucleotide sequence similarities between the major structural genes of CS20 (csnA), CS18 (fotA), CS12 (cswA), and porcine antigen 987 (fasA) was developed and used to screen a collection of 266 LT-secreting ETEC isolates in which no known CFA was detected. PCRamplified products of different molecular masses were obtained from 49 (18.4%) isolates. Nucleotide sequence analysis of the PCR amplicons followed by GenBank nucleotide BLASTn analysis revealed five novel DNA sequences; translated amino acid BLASTx analysis confirmed sequence similarity to class 1b major structural proteins encoded by csnA, fotA, and fasA. Strains expressing the novel CFAs were phylotyped and analyzed using multilocus sequence typing (MLST; Achtman scheme), and the types detected were compared to those of a collection of archived global E. coli strains. In conclusion, application of the degenerate primer sets to ETEC isolates from surveillance studies increased the total number of ETEC isolates with detectable CFAs by almost 20%. Additionally, MLST analysis suggests that for many CFAs, there may be a requirement for certain genetic backgrounds to acquire and maintain plasmids carrying genes encoding CFAs. Copyright © 2011, American Society for Microbiology.
Pomerantsev A.P.,National Institute of Allergy and Infectious Diseases |
Pomerantseva O.M.,Biological Defense Research Directorate |
Moayeri M.,National Institute of Allergy and Infectious Diseases |
Fattah R.,National Institute of Allergy and Infectious Diseases |
And 2 more authors.
Protein Expression and Purification | Year: 2011
Bacillus anthracis produces a number of extracellular proteases that impact the integrity and yield of other proteins in the B. anthracis secretome. In this study we show that anthrolysin O (ALO) and the three anthrax toxin proteins, protective antigen (PA), lethal factor (LF), and edema factor (EF), produced from the B. anthracis Ames 35 strain (pXO1 +, pXO2 -), are completely degraded at the onset of stationary phase due to the action of proteases. An improved Cre-loxP gene knockout system was used to sequentially delete the genes encoding six proteases (InhA1, InhA2, camelysin, TasA, NprB, and MmpZ). The role of each protease in degradation of the B. anthracis toxin components and ALO was demonstrated. Levels of the anthrax toxin components and ALO in the supernatant of the sporulation defective, pXO1 + A35HMS mutant strain deleted for the six proteases were significantly increased and remained stable over 24 h. A pXO1-free variant of this six-protease mutant strain, designated BH460, provides an improved host strain for the preparation of recombinant proteins. As an example, BH460 was used to produce recombinant EF, which previously has been difficult to obtain from B. anthracis. The EF protein produced from BH460 had the highest in vivo potency of any EF previously purified from B. anthracis or Escherichia coli hosts. BH460 is recommended as an effective host strain for recombinant protein production, typically yielding greater than 10 mg pure protein per liter of culture. © 2011 Elsevier Inc. All rights reserved.
Zwick M.E.,Emory University |
Zwick M.E.,Biological Defense Research Directorate |
Joseph S.J.,Emory University |
Didelot X.,University of Oxford |
And 18 more authors.
Genome Research | Year: 2012
The key genes required for Bacillus anthracis to cause anthrax have been acquired recently by horizontal gene transfer. To understand the genetic background for the evolution of B. anthracis virulence, we obtained high-redundancy genome sequences of 45 strains of the Bacillus cereus sensu lato (s.l.) species that were chosen for their genetic diversity within the species based on the existing multilocus sequence typing scheme. From the resulting data, we called more than 324,000 new genes representing more than 12,333 new gene families for this group. The core genome size for the B. cereus s.l. group was ∼1750 genes, with another 2150 genes found in almost every genome constituting the extended core. There was a paucity of genes specific and conserved in any clade. We found no evidence of recent large-scale gene loss in B. anthracis or for unusual accumulation of nonsynonymous DNA substitutions in the chromosome; however, several B. cereus genomes isolated from soil and not previously associated with human disease were degraded to various degrees. Although B. anthracis has undergone an ecological shift within the species, its chromosome does not appear to be exceptional on a macroscopic scale compared with close relatives.
Read T.D.,Biological Defense Research Directorate |
Read T.D.,Emory University |
Turingan R.S.,NetBio, Inc. |
Cook C.,Biological Defense Research Directorate |
And 5 more authors.
PLoS ONE | Year: 2010
Background: Multiple locus sequence typing (MLST) has become a central genotyping strategy for analysis of bacterial populations. The scheme involves de novo sequencing of 6-8 housekeeping loci to assign unique sequence types. In this work we adapted MLST to a rapid microfluidics platform in order to enhance speed and reduce laboratory labor time. Methodology/Principal Findings: Using two integrated microfluidic devices, DNA was purified from 100 Bacillus cereus soil isolates, used as a template for multiplex amplification of 7 loci and sequenced on forward and reverse strands. The time on instrument from loading genomic DNA to generation of electropherograms was only 1.5 hours. We obtained full-length sequence of all seven MLST alleles from 84 representing 46 different Sequence Types. At least one allele could be sequenced from a further 15 strains. The nucleotide diversity of B. cereus isolated in this study from one location in Rockville, Maryland (0.04 substitutions per site) was found to be as great as the global collection of isolates. Conclusions/Significance: Biogeographical investigation of pathogens is only one of a panoply of possible applications of microfluidics based MLST; others include microbiologic forensics, biothreat identification, and rapid characterization of human clinical samples. © 2010 Read et al.
Albrecht M.T.,Biological Defense Research Directorate |
Albrecht M.T.,Biomedical Advanced Research and Development Authority |
Eyles J.E.,UK Defence Science and Technology Laboratory |
Eyles J.E.,Pfizer |
And 3 more authors.
FEMS Immunology and Medical Microbiology | Year: 2012
The efficacy of multi-agent DNA vaccines consisting of a truncated gene encoding Bacillus anthracis lethal factor (LFn) fused to either Yersinia pestis V antigen (V) or Y. pestis F1 was evaluated. A/J mice were immunized by gene gun and developed predominantly IgG1 responses that were fully protective against a lethal aerosolized B. anthracis spore challenge but required the presence of an additional DNA vaccine expressing anthrax protective antigen to boost survival against aerosolized Y. pestis. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.