[Show abstract][Hide abstract] ABSTRACT: Emerging B. cereus strains that cause anthrax-like disease have been isolated in Cameroon (CA strain) and Côte d'Ivoire (CI strain). These strains are unusual, because their genomic characterisation shows that they belong to the B. cereus species, although they harbour two plasmids, pBCXO1 and pBCXO2, that are highly similar to the pXO1 and pXO2 plasmids of B. anthracis that encode the toxins and the polyglutamate capsule respectively. The virulence factors implicated in the pathogenicity of these B. cereus bv anthracis strains remain to be characterised. We tested their virulence by cutaneous and intranasal delivery in mice and guinea pigs; they were as virulent as wild-type B. anthracis. Unlike as described for pXO2-cured B. anthracis, the CA strain cured of the pBCXO2 plasmid was still highly virulent, showing the existence of other virulence factors. Indeed, these strains concomitantly expressed a hyaluronic acid (HA) capsule and the B. anthracis polyglutamate (PDGA) capsule. The HA capsule was encoded by the hasACB operon on pBCXO1, and its expression was regulated by the global transcription regulator AtxA, which controls anthrax toxins and PDGA capsule in B. anthracis. Thus, the HA and PDGA capsules and toxins were co-regulated by AtxA. We explored the respective effect of the virulence factors on colonisation and dissemination of CA within its host by constructing bioluminescent mutants. Expression of the HA capsule by itself led to local multiplication and, during intranasal infection, to local dissemination to the adjacent brain tissue. Co-expression of either toxins or PDGA capsule with HA capsule enabled systemic dissemination, thus providing a clear evolutionary advantage. Protection against infection by B. cereus bv anthracis required the same vaccination formulation as that used against B. anthracis. Thus, these strains, at the frontier between B. anthracis and B. cereus, provide insight into how the monomorphic B. anthracis may have emerged.
[Show abstract][Hide abstract] ABSTRACT: Anthrax is a fatal disease caused by strains of Bacillus anthracis. Members of this monophyletic species are non motile and are all characterized by the presence of four prophages and a nonsense mutation in the plcR regulator gene. Here we report the complete genome sequence of a Bacillus strain isolated from a chimpanzee that had died with clinical symptoms of anthrax. Unlike classic B. anthracis, this strain was motile and lacked the four prohages and the nonsense mutation. Four replicons were identified, a chromosome and three plasmids. Comparative genome analysis revealed that the chromosome resembles those of non-B. anthracis members of the Bacillus cereus group, whereas two plasmids were identical to the anthrax virulence plasmids pXO1 and pXO2. The function of the newly discovered third plasmid with a length of 14 kbp is unknown. A detailed comparison of genomic loci encoding key features confirmed a higher similarity to B. thuringiensis serovar konkukian strain 97-27 and B. cereus E33L than to B. anthracis strains. For the first time we describe the sequence of an anthrax causing bacterium possessing both anthrax plasmids that apparently does not belong to the monophyletic group of all so far known B. anthracis strains and that differs in important diagnostic features. The data suggest that this bacterium has evolved from a B. cereus strain independently from the classic B. anthracis strains and established a B. anthracis lifestyle. Therefore we suggest to designate this isolate as "B. cereus variety (var.) anthracis".
PLoS ONE 07/2010; 5(7):e10986. DOI:10.1371/journal.pone.0010986 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Culturable microorganisms from various samples taken at an active factory performing wool and goat hair cleaning were isolated and analyzed. Bacillus anthracis was found in air filter dust, wastewater, and goat hairs, where it accounted for approximately 1% of the total counts of viable bacteria. Consistent with the countries of origin of the processed material (South Caucasian and Middle Eastern), all B. anthracis isolates belonged to the same phylogenetic cluster, as determined by variable-number tandem repeat (VNTR) typing at eight loci. Within this cluster, five closely related VNTR subtypes could be identified, of which two were previously unreported. Additional diversity was observed when more sensitive genetic markers were assayed, demonstrating the multifocal nature of goat hair contamination. Goat hair originating from areas where anthrax is endemic remains a material with high biological risk for modern woolworkers.
[Show abstract][Hide abstract] ABSTRACT: We evaluated real-time PCR assays for the detection of C. burnetii which targets sequences that are present either in one (icd) or in several copies (transposase of IS1111a) on the chromosome. The assays are highly sensitive, with reproducible detection limits of approximately 10 copies per reaction, at least 100 times more sensitive than capture ELISA, when performed on infected placenta material and specific for C. burnetii. The numbers of IS1111 elements in the genomes of 75 C. burnetii isolates were quantified by real-time PCR and proved to be highly variable.
Annals of the New York Academy of Sciences 11/2006; 1078(1):563-5. DOI:10.1196/annals.1374.111 · 4.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To evaluate different methods that are useful for rapid and definitive discrimination of Bacillus anthracis from other bacteria of the Bacillus cereus group in environmental samples like letters claimed to contain anthrax spores.
Characterized strains and bacteria from environmental samples were analysed by microbiological and molecular methods (PCR and restriction analysis). Environmental isolates often shared several microbiological features with B. anthracis, e.g. lack of beta-haemolysis and phospholipase C activity, and only the gamma phage assay was specific for B. anthracis. PCR assays targeting markers from the virulence plasmids exclusively detected B. anthracis, but other PCR targets were also detected in nonanthrax isolates. Additionally, the restriction pattern in an AluI restriction analysis of the SG-749 fragment is not 100% specific. The loci used for multiple-locus variable-number tandem repeat analysis of B. anthracis are also present in other members of the B. cereus group, but amplicon sizes are usually different.
Environmental samples often contain borderline isolates closely related to B. anthracis both on microbiological and genetic levels. Real-time PCR targeting plasmidal and chromosomal markers should be used for rapid and definitive exclusion of a virulent strain of B. anthracis in such samples.
This study gives an overview of the current microbiological and molecular methods used for identification of B. anthracis and shows that most assays have limits when borderline isolates present in environmental samples are analysed.
[Show abstract][Hide abstract] ABSTRACT: Coxiella burnetii, the bacterium causing Q fever, is an obligate intracellular biosafety level 3 agent. Detection and quantification of these bacteria with conventional methods is time consuming and dangerous. During the last years, several PCR based diagnostic assays were developed to detect C. burnetii DNA in cell cultures and clinical samples. We developed and evaluated TaqMan-based real-time PCR assays that targeted the singular icd (isocitrate dehydrogenase) gene and the transposase of the IS1111a element present in multiple copies in the C. burnetii genome.
To evaluate the precision of the icd and IS1111 real-time PCR assays, we performed different PCR runs with independent DNA dilutions of the C. burnetii Nine Mile RSA493 strain. The results showed very low variability, indicating efficient reproducibility of both assays. Using probit analysis, we determined that the minimal number of genome equivalents per reaction that could be detected with a 95% probability was 10 for the icd marker and 6.5 for the IS marker. Plasmid standards with cloned icd and IS1111 fragments were used to establish standard curves which were linear over a range from 10 to 10(7) starting plasmid copy numbers. We were able to quantify cell numbers of a diluted, heat-inactivated Coxiella isolate with a detection limit of 17 C. burnetii particles per reaction. Real-time PCR targeting both markers was performed with DNA of 75 different C. burnetii isolates originating from all over the world. Using this approach, the number of IS1111 elements in the genome of the Nine Mile strain was determined to be 23, close to 20, the number revealed by genome sequencing. In other isolates, the number of IS1111 elements varied widely (between seven and 110) and seemed to be very high in some isolates.
We validated TaqMan-based real-time PCR assays targeting the icd and IS1111 markers of C. burnetii. The assays were shown to be specific, highly sensitive and efficiently reproducible. Cell numbers in dilutions of a C. burnetii isolate were reliably quantified. PCR quantification suggested a high variability of the number of IS1111 elements in different C. burnetii isolates, which may be useful for further phylogenetic studies.
[Show abstract][Hide abstract] ABSTRACT: A novel porcine gammaherpesvirus was detected in the blood of domestic pigs by PCR. With degenerate-primer PCR and subsequent long-distance PCR approaches a 60-kbp genome stretch was amplified. Sequence analysis revealed the presence of the gammaherpesvirus ORFs 03 to 46 as well as a putative chemokine receptor and a v-bcl-2 gene. The 60-kbp sequence was compared with the corresponding sequence of the porcine lymphotropic herpesvirus 1 (PLHV-1) published recently and the sequence of PLHV-2, which was amplified from porcine tonsil. Considerable sequence differences (amino acid identities: 49-89%) were found between the novel virus and PLHV-1 as well as PLHV-2, which were very closely related to each other (amino acid identities: 85-98%). The novel virus had essentially the same genome organization as PLHV-1 and -2 and was therefore designated PLHV-3. Like PLHV-1 and -2, PLHV-3 was frequently found in the blood and in lymphoid organs of domestic and feral pigs from different geographic locations. In the blood, the PLHVs were detected predominantly in B-cells. Indication for latent as well as productive PLHV-3 infection was found in the porcine B-cell line L23. It can be concluded that the PLHVs are widespread and are likely to cause a persistent B-lymphotropic infection. Since PLHV-1 has been implicated in the development of porcine posttransplantation lymphoproliferative disease, all porcine lymphotropic gammaherpesviruses are of concern when pigs are used as donors in xenotransplantation.