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P2-202 Comparative Analysis of Clostridium sporogenes PA3679 Strains from Different Sources Using Pulsed-field Gel Electrophoresis (PFGE) and Whole Genome Sequencing (WGS)

Monday, July 27, 2015
Exhibit Hall (Oregon Convention Center)
Kristin Schill , U. S. Food and Drug Administration , Bedford Park , IL
Yun Wang , U.S. Food and Drug Administration , Bedford Park , IL
Jean-Francois Pombert
Robert Butler
Guy Skinner , U.S. Food and Drug Administration , Bedford Park , IL
Rukma Reddy , U.S. Food and Drug Administration , Bedford Park , IL
John Larkin , Food Protection and Defense Institute , St. Paul , MN
Introduction: Clostridium sporogenes PA3679 has historically been used as a surrogate for proteolytic Clostridium botulinum strains to validate thermal processing. It has been suggested that C. sporogenes PA3679 is a proteolytic C. botulinum strain that has lost the neurotoxin gene cluster, but the true taxonomic classification of PA3679 remains unclear.

Purpose: The objective was to obtain cultures of C. sporogenes PA3679 from various sources and perform comparative genomic analysis to assess the genetic variability among the strains.

Methods: Pulsed-field gel electrophoresis (PFGE) was performed on C. sporogenes PA3679 strains collected from five different sources. Whole genome sequencing was conducted using an Illumina MiSeq. The phylogenetic relatedness and genetic variability was assessed based on the 16S rDNA sequencing and whole genome single nucleotide polymorphism (SNP) analysis.

Results: All C. sporogenes PA3679 strains from five sources were categorized into 2 groups (group I: ATCC7955 NCA3679 1961, 1961-2, 1990, and 2007; group II: NFL, UW, FDA, Campbell, and ATCC7955 NCA3679 1961-4). The 16S ML tree illustrated that both groups of isolates clustered with proteolytic C. botulinum, but group I strains formed a distinct cluster with other non-PA3679 C. sporogenes strains. SNP analysis revealed that group I strains were more similar to the reference PA3679 genome (GenBank accession: AGAH00000000) than group II isolates.

Significance: Based on the genetic characterization of the C. sporogenes strains in this study we conclude that the reference C. sporogenes PA3679 genome and the group I C. sporogenes strains were genetically distinct from strains obtained from four other sources (UW, NFL, FDA and Campbell Soup Company). Considering the widespread use of C. sporogenes PA3679 and its genetic information in numerous studies aimed at understanding the taxonomy of C. botulinum and related species and validating thermal processing technologies, the accurate identification and thorough genetic characterization of C. sporogenes PA3679 is warranted.

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