Abstract
BackgroundThailand has had several foodborne outbreaks of botulism, one of the biggest being in 2006 when laboratory investigations identified the etiologic agent as Clostridium botulinum type A. Identification of the etiologic agent from outbreak samples is laborious using conventional microbiological methods and the neurotoxin mouse bioassay. Advances in molecular techniques have added enormous information regarding the etiology of outbreaks and characterization of isolates. We applied these methods in three outbreaks of botulism in Thailand in 2010.Methodology/Principal FindingsA total of 19 cases were involved (seven each in Lampang and Saraburi and five in Maehongson provinces). The first outbreak in Lampang province in April 2010 was associated with C. botulinum type F, which was detected by conventional methods. Outbreaks in Saraburi and Maehongson provinces occurred in May and December were due to C. botulinum type A1(B) and B that were identified by conventional methods and molecular techniques, respectively. The result of phylogenetic sequence analysis showed that C. botulinum type A1(B) strain Saraburi 2010 was close to strain Iwate 2007. Molecular analysis of the third outbreak in Maehongson province showed C. botulinum type B8, which was different from B1–B7 subtype. The nontoxic component genes of strain Maehongson 2010 revealed that ha33, ha17 and botR genes were close to strain Okra (B1) while ha70 and ntnh genes were close to strain 111 (B2).Conclusion/SignificanceThis study demonstrates the utility of molecular genotyping of C. botulinum and how it contributes to our understanding the epidemiology and variation of boNT gene. Thus, the recent botulism outbreaks in Thailand were induced by various C. botulinum types.
Highlights
In the past, Thailand has experienced several foodborne outbreaks of botulism
From Lampang province outbreak, C.botulinum type F was identified in one sample each of wild boar meat and sour pork by enzyme-linked immunosorbent assay (ELISA) and mouse bioassay, but these samples were negative in the culture method
The positive result samples (one plastic-wrapped pork sausage (F1) and two stool specimens (S1, S2)) from Saraburi province outbreak and positive result samples (two fermented soy bean samples (F1, F2) and two stool specimens (S1, S2)) from Maehongson province outbreak were detected as C. botulinum type A and B by ELISA and mouse bioassay, and isolated C.botulinum from positive samples (Table 2)
Summary
Thailand has experienced several foodborne outbreaks of botulism. During December 1997, six people from the Maesot district in Tak province found ill after consumption of homemade canned bamboo shoots. In vitro methods such as enzyme-linked immunosorbent assay (ELISA) [7,8,9] and an assay with a large immune-sorbent surface area (ALISSA) [10] require only 5–6 hrs for the detection and are as sensitive as the mouse bioassay [7,8,9]. They are rapid and have a wider detection range including foods, environmental and sera samples [7,8,9,10]. We applied these methods in three outbreaks of botulism in Thailand in 2010
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