Lethal outbreak of infection with Clostridium novyi type A and other spore-forming organisms in Scottish injecting drug users

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Abstract
This report describes the investigation and management of an unprecedented outbreak of severe illness among injecting drug users (IDUs) in Scotland during April to August 2000. IDUs with severe soft tissue inflammation were prospectively sought among acute hospitals and a mortuary in Scotland. Cases were categorised as definite or probable: probable cases had severe injection site inflammation or multi-system failure; definite cases had both. Information about clinical course, mortality, post-mortem findings and laboratory data was gathered by standardised case-note review and interview. Sixty cases were identified – 23 definite and 37 probable. Most had familial or social links with each other and 50 were from Glasgow. Median age was 30 years; 31 were female. The majority, especially definite cases, injected heroin/citric acid extravascularly. Of definite cases, 20 died (87% case-fatality rate; 13 after intensive care), 15 had necrotising fasciitis, 22 had injection site oedema and 13 had pleural effusion. Median white cell count was 60×109/L. Of 37 probable cases, three died (8% case-fatality rate). Overall, the most frequently isolated pathogen was Clostridium novyi type A (13 cases: 8 in definite cases). The findings are consistent with an infection resulting from injection into soft tissue of acidified heroin contaminated with spore-forming bacteria. Toxin production led to a severe local reaction and, in many, multi-system failure.