Furthermore, BoNT serotypes are divided into subtypes
based on their nucleic acid and amino acid sequence
heterogeneity (Hill and Smith, 2013). Remarkable morphological
and physiological differences are seen between C. botulinum strains isolated from different sources. Four
physiologically different BoNT producing groups of
C. botulinum (I–IV) are described (Hatheway, 1990;
Rossetto et al., 2014). Modern comparative sequence
analysis also confirms that there are significant genetic
differences between these groups (Rossetto et al., 2014).
These findings also point to the fact that at present several
different Clostridium species, the common characteristic
of which is the production of orally effective neurotoxins,
are subsumed under the name C. botulinum. Additionally,
some strains of C. baratii and C. butyricum produce
BoNT of the serotypes F and E, respectively