Community-associated Clostridium difficile infection among older people in Tayside, Scotland, is associated with antibiotic exposure and care home residence: cohort study with nested case-control.

OBJECTIVES: To estimate the risks of community-associated Clostridium difficile infection (CA-CDI) among the population aged ≥ 65 years associated with antibiotic exposure and care home residence. POPULATION AND METHODS: We linked cases from a prospective study in Tayside, Scotland from 1 November 2008 to 31 October 2009 to population datasets to conduct a cohort study and a nested, matched (1 : 10 by age and gender) case-control study. RESULTS: There were 79,039 eligible residents. CA-CDI incidence was 20.3/10,000 person years. In the cohort study, after adjustment, we found a significantly increasing risk of CA-CDI with increasing age and comorbidity, prior hospital admission, care home residence [hazard ratio (HR) 1.96, 95% CI 1.14-3.34] and baseline antibiotic exposure (1.94, 1.35-2.77). In separate adjusted models, '4C' antibiotics (clindamycin, co-amoxiclav, cephalosporins, ciprofloxacin; 2.75, 1.78-4.26) and fluoroquinolones (3.33, 1.95-5.67) had higher associated risks. We matched 62 CA-CDI cases without recent (prior 3 months) hospital admission to 620 controls. In adjusted logistic regression models, exposure to any antibiotics increased the risk of CA-CDI (OR 6.04, 95% CI 3.19-11.43). Exposure to 4C antibiotics or fluoroquinolones had higher associated risks: adjusted OR 11.60 (95% CI 5.57-24.15) and 13.04 (4.91-34.64), respectively. Risk of CA-CDI increased with cumulative antibiotic exposure. Subgroup analysis of 42 cases with C. difficile cultured and 420 controls amplified all associations between antibiotic exposure and CA-CDI. Care home residence independently increased the risk of CA-CDI in all models. CONCLUSIONS: Our results have two important implications. First, they validate the classification of 4C antibiotics and fluoroquinolones in primary care as high risk for CA-CDI. Second, they demonstrate the importance of prior antibiotic exposure and place of residence for risk assessment by primary care prescribers.

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

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 x 10(9)/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.