Survival analysis for respiratory failure in patients with food-borne botulism

Botulism is a rare presynaptic neuromuscular junction disorder caused by potent toxins produced by the anaerobic, spore-forming, Gram-positive bacterium Clostridium botulinum. Food-borne botulism is caused by the ingestion of foods contaminated with botulinum toxin. In March 2006, there was a large outbreak of food-borne botulism associated with the ingestion of home-canned bamboo shoots in Thailand. The survival analyses for respiratory failure in these patients were studied and are reported here.

A prospective observational cohort study was conducted on this outbreak. The primary outcome of interest was the time to respiratory failure. The secondary outcome was the time to weaning off ventilator. The prognostic factors associated with respiratory failure and weaning off ventilator are presented.

A total of 91 in-patients with baseline clinical characteristics were included. Most cases first presented with gastrointestinal symptoms followed by neurological symptoms, the most striking of which being difficulty in swallowing. Common clinical features included ptosis, ophthalmoplegia, proximal muscle weakness, pupillary abnormality, and respiratory failure. Forty-two patients developed respiratory failure requiring mechanical ventilation and the median duration on ventilator was 14 days. The median length of hospital stay for all patients was 13.5 days. Difficulty in breathing, moderate to severe ptosis, and dilated and fixed pupils were associated with respiratory failure. Among patients who were on ventilators, a short incubation period and pupillary abnormality were associated with a longer period of mechanical ventilation. All patients had antitoxin injection and there was no mortality in this outbreak.

The history of difficult breathing and the findings of moderate to severe ptosis and pupillary abnormality were associated with severe illness and respiratory failure. A long incubation time was associated with a better prognosis. Although botulism is a potentially fatal disease, there was no mortality in this outbreak. All patients had antitoxin injection and good intensive care that resulted in good clinical outcomes.