Analysis of genomic differences among Clostridium botulinum type A1 strains

<p>Abstract</p> <p>Background</p> <p>Type A1 <it>Clostridium botulinum </it>strains are a group of Gram-positive, spore-forming anaerobic bacteria that produce a genetically, biochemically, and biophysically indistinguishable 150 kD protein that causes botulism. The genomes of three type A1 <it>C. botulinum </it>strains have been sequenced and show a high degree of synteny. The purpose of this study was to characterize differences among these genomes and compare these differentiating features with two additional unsequenced strains used in previous studies.</p> <p>Results</p> <p>Several strategies were deployed in this report. First, University of Massachusetts Dartmouth laboratory Hall strain (UMASS strain) neurotoxin gene was amplified by PCR and sequenced; its sequence was aligned with the published ATCC 3502 Sanger Institute Hall strain and Allergan Hall strain neurotoxin gene regions. Sequence alignment showed that there was a synonymous single nucleotide polymorphism (SNP) in the region encoding the heavy chain between Allergan strain and ATCC 3502 and UMASS strains. Second, comparative genomic hybridization (CGH) demonstrated that the UMASS strain and a strain expected to be derived from ATCC 3502 in the Centers for Disease Control and Prevention (CDC) laboratory (ATCC 3502*) differed in gene content compared to the ATCC 3502 genome sequence published by the Sanger Institute. Third, alignment of the three sequenced <it>C. botulinum </it>type A1 strain genomes revealed the presence of four comparable blocks. Strains ATCC 3502 and ATCC 19397 share the same genome organization, while the organization of the blocks in strain Hall were switched. Lastly, PCR was designed to identify UMASS and ATCC 3502* strain genome organizations. The PCR results indicated that UMASS strain belonged to Hall type and ATCC 3502* strain was identical to ATCC 3502 (Sanger Institute) type.</p> <p>Conclusions</p> <p>Taken together, <it>C. botulinum </it>type A1 strains including Sanger Institute ATCC 3502, ATCC 3502*, ATCC 19397, Hall, Allergan, and UMASS strains demonstrate differences at the level of the neurotoxin gene sequence, in gene content, and in genome arrangement.</p

Distinct Binding and Immunogenic Properties of the Gonococcal Homologue of Meningococcal Factor H Binding Protein

Neisseria meningitidis is a leading cause of sepsis and meningitis. The bacterium recruits factor H (fH), a negative regulator of the complement system, to its surface via fH binding protein (fHbp), providing a mechanism to avoid complement-mediated killing. fHbp is an important antigen that elicits protective immunity against the meningococcus and has been divided into three different variant groups, V1, V2 and V3, or families A and B. However, immunisation with fHbp V1 does not result in cross-protection against V2 and V3 and vice versa. Furthermore, high affinity binding of fH could impair immune responses against fHbp. Here, we investigate a homologue of fHbp in Neisseria gonorrhoeae, designated as Gonococcal homologue of fHbp (Ghfp) which we show is a promising vaccine candidate for N. meningitidis. We demonstrate that Gfhp is not expressed on the surface of the gonococcus and, despite its high level of identity with fHbp, does not bind fH. Substitution of only two amino acids in Ghfp is sufficient to confer fH binding, while the corresponding residues in V3 fHbp are essential for high affinity fH binding. Furthermore, immune responses against Ghfp recognise V1, V2 and V3 fHbps expressed by a range of clinical isolates, and have serum bactericidal activity against N. meningitidis expressing fHbps from all variant groups

Sequence Diversity of Genes Encoding Botulinum Neurotoxin Type F ▿ †

Botulism due to type F botulinum neurotoxin (BoNT/F) is rare (<1% of cases), and only a limited number of clostridial strains producing this toxin type have been isolated. As a result, analysis of the diversity of genes encoding BoNT/F has been challenging. In this study, the entire bont/F nucleotide sequences were determined from 33 type F botulinum toxin-producing clostridial strains isolated from environmental sources and botulism outbreak investigations. We examined proteolytic and nonproteolytic Clostridium botulinum type F strains, bivalent strains, including Bf and Af, and Clostridium baratii type F strains. Phylogenetic analysis revealed that the bont/F genes examined formed 7 subtypes (F1 to F7) and that the nucleotide sequence identities of these subtypes differed by up to 25%. The genes from proteolytic (group I) C. botulinum strains formed subtypes F1 through F5, while the genes from nonproteolytic (group II) C. botulinum strains formed subtype F6. Subtype F7 was composed exclusively of bont/F genes from C. baratii strains. The region of the bont/F5 gene encoding the neurotoxin light chain was found to be highly divergent compared to the other subtypes. Although the bont/F5 nucleotide sequences were found to be identical in strains harboring this gene, the gene located directly upstream (ntnh/F) demonstrated sequence variation among representative strains of this subtype. These results demonstrate that extensive nucleotide diversity exists among genes encoding type F neurotoxins from strains with different phylogenetic backgrounds and from various geographical sources

First Report Worldwide of an Infant Botulism Case Due to Clostridium botulinum Type E▿

Clostridium botulinum type E has been associated with botulism in adults but never in infants. Infant botulism type E cases have been associated with neurotoxigenic strains of C. butyricum. We report the first infant botulism case due to C. botulinum type E worldwide