Diversity of Group I and II Clostridium botulinum Strains from France Including Recently Identified Subtypes

Abstract

In France, human botulism is mainly food-borne intoxication, whereas infant botulism is rare. A total of 99 group I and II Clostridium botulinum strains including 59 type A (12 historical isolates [1947–1961], 43 from France [1986–2013], 3 from other countries, and 1 collection strain), 31 type B (3 historical, 23 recent isolates, 4 from other countries, and 1 collection strain), and 9 type E (5 historical, 3 isolates, and 1 collection strain) were investigated by botulinum locus gene sequencing and multilocus sequence typing analysis. Historical C. botulinum A strains mainly belonged to subtype A1 and sequence type (ST) 1, whereas recent strains exhibited a wide genetic diversity: subtype A1 in orfX or ha locus, A1(B), A1(F), A2, A2b2, A5(B2′) A5(B3′), as well as the recently identified A7 and A8 subtypes, and were distributed into 25 STs. Clostridium botulinum A1(B) was the most frequent subtype from food-borne botulism and food. Group I C. botulinum type B in France were mainly subtype B2 (14 out of 20 historical and recent strains) and were divided into 19 STs. Food-borne botulism resulting from ham consumption during the recent period was due to group II C. botulinum B4. Type E botulism is rare in France, 5 historical and 1 recent strains were subtype E3. A subtype E12 was recently identified from an unusual ham contamination. Clostridium botulinum strains from human botulism in France showed a wide genetic diversity and seems to result not from a single evolutionary lineage but from multiple and independent genetic rearrangements.

Impact of Clostridium botulinum genomic diversity on food safety

“…These have included comparative genomic indexing (using a DNA microarray), multi-locus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE), multi-locus variable number tandem repeat analysis (MVLA), amplified fragment length polymorphism (AFLP), and comparisons of core genome single nucleotide polymorphisms (SNPs) following whole genome sequencing [2, 5, 6•, 7•, 22, 43•, 44, 45, 46, 47]. These approaches typically separate strains in up to about ten lineages or clusters (depending on strains tested and criterion applied).…”

“…The other cluster includes subtype B4 strains and type E strains (Figure 2, panel b). This includes type E strains, isolated in France and Argentina [43•, 57, 58], that form neurotoxin subtype E9 or E12 (two closely related neurotoxins that are separate from other type E neurotoxins — Figure 1). Three further type E strains isolated from a food sample (whale meat) collected during a foodborne botulism outbreak are also closely related to type B strains [43•, 54•].…”

“…This includes type E strains, isolated in France and Argentina [43•, 57, 58], that form neurotoxin subtype E9 or E12 (two closely related neurotoxins that are separate from other type E neurotoxins — Figure 1). Three further type E strains isolated from a food sample (whale meat) collected during a foodborne botulism outbreak are also closely related to type B strains [43•, 54•]. These unusual type E strains have presumably acquired neurotoxin genes by horizontal gene transfer, and represent rare examples of gene transfer between the type E cluster and the clusters dominated by subtype B4 strains (Figure 2, panel b).…”

“…[4, 5, 7•, 22, 43•, 44, 55, 56, 66]). For example, lineages with Group I strains forming subtype A1 or A2 neurotoxins have been found throughout the world.…”

Botulinum Toxins, Diversity, Mode of Action, Epidemiology of Botulism in France

“…The diversity of BoNT types and subtypes as well as of the BoNT-producing clostridia reflects the diverse origins of human botulism in France [146].…”