Investigations
1st investigations to order
mouse bioassay of serum, gastric secretions, stool, or food samples
Test
Performed in all patients with suspected botulism. Confirmation and toxin typing are obtained in almost 75% of cases.[52] Unfortunately, depending on sample toxin concentration, symptoms in mice may not be evident for 24 to 48 hours.
The mouse bio-assay is labour and resource intensive, and therefore the testing is performed in a limited number of public health laboratories.
Details on sample preparation and transport can be obtained by consulting resources such as the British Columbia Centre for Disease Control, and contacting local or state public health departments.[53] British Columbia Centre for Disease Control: laboratory services Opens in new window In the US, this is the Centers for Disease Control and Prevention. CDC: Information for health professionals: botulism Opens in new window
Result
identifies toxin of Clostridium botulinum
culture of food samples, gastric aspirates, or faecal material
Test
Performed in cases of foodborne or infant botulism.
On egg yolk medium, growth may exhibit an iridescence that follows the irregular contour of the colony.
C botulinum types C, D, and E colonies are surrounded by a wide zone (2-4 mm) of yellow precipitate, while colonies of types A and B demonstrate a smaller zone.
Other members of the genus Clostridium produce colonies with similar morphological characteristics but do not produce toxins.
Strict anaerobic conditions are required for growth, and competing faecal flora or non-toxigenic C botulinum strains may make isolation difficult.
Overall sensitivity is 67% to 73%.[60]
Result
identifies toxin of Clostridium botulinum
Investigations to consider
electrophysiological testing
Test
This test is very uncomfortable and should not be requested unless botulism or Lambert-Eaton myasthenic syndrome is a serious consideration.
Sensory nerve studies are normal.
Motor conduction velocities are normal, while the amplitude of compound muscle action potentials is reduced in 85% of cases.[54]
Repetitive nerve stimulation at high rates (≥20 Hz) may reveal a small increment in the motor response.
Post-tetanic facilitation is 30% to 100% in botulism, and may last for several minutes.
Result
small muscle action potential in response to supramaximal nerve stimulus of a clinically affected muscle
Emerging tests
enzyme-linked immunosorbent assay (ELISA)
Test
ELISA has demonstrated botulinum toxin in contaminated food samples such as fish fillets, tinned salmon and corned beef, pasta products, and tinned vegetables.[55][56][57][58]
The utility of ELISA has been limited in food substances with endogenous proteinases (e.g., egg yolk, milk) and clinical specimens such as serum or faeces.[61]
Result
identifies toxin of Clostridium botulinum
polymerase chain reaction (PCR)
Test
Cellular components of clinical and food samples may limit PCR sensitivity. Greater sensitivity may be achieved with extracted DNA, but the process can be laborious and time-consuming.[59]
Result
identifies toxin of Clostridium botulinum
Use of this content is subject to our disclaimer