Space-Time Relations of Clostridium difficile cases within a health economy: A Social Network Analysis

Presented by Mark Reacher network analysis by Iain Roddick Wendy Rice, Rowan Slowther, Judy Ames, Giri Shankar

Clostridium difficile natural history • A common antibiotic associated infectious diarrhoea

• Transmission by ingestion of toxin producing spores in faeces of an infected case.

• Spores may remain “dormant” in large gut as part of microbiota until …..

• Antibiotic treatment perturbs large gut microflora, spores no longer held in check and proliferate causing Clostridium difficile Associated Disease

2 Space-Time Relations of Clostridium difficile cases within a health economy: A Social Network Analysis

Clostridium difficile Associated Disease (CTAD)

Comprises a wide range of illness from self limiting diarrhoea to severe protracted diarrhoea, fluid loss , toxic shock, toxic megacolon (requiring life saving colectomy) and acute death.

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Clostridium difficile control

• Universal infection control essential including hand hygiene in care staff : cleaning lavatories and all sanitation surfaces wards and fomites - oxidising disinfectants as well as physical cleaning with detergent required to destroy spores

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BBC Friday, 5 November, 2004Hospital superbug must be halved. Bloodstream infections with the hospital superbug MRSA must be halved in three years, the government has said. Health Secretary John Reid tasked NHS hospitals with achieving a year on year reduction up to and beyond March 2008.

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Development of Health care associated infections Mandatory surveillance

2004 April CDI > 65 years; MRSA bacteraemia

2005 April Enhanced MRSA bacteraemia

2007 April CDI > 2 years

2011 January MSSA and E.coli bacteraemia added

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Attributing site of acquisition of infectionCases of Clostridium difficile infection occurring

within 72 hours of admission have been regarded as acquiring infection prior to admission to that hospital – at another hospital or in the community

Hospitals have only been held accountable for infections occurring greater than 72 hours following admission

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Clostridium difficile reports mandatory surveillance 2007 to 2013 in England

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2007-8 2008-9 2009-10 2010-11 2011-12 2012-130

10000

20000

30000

40000

50000

60000

Total Trust apportioned

Examination of space time relations of Community attributed Clostridium difficile cases

A substantial proportion of Clostridium difficile cases arising

in the North Norfolk health economy were attributed to acquisition in the community

Community health services in Norfolk recorded the dates of arrival and discharge in care settings and to home for all new cases of Clostridium difficile infection diagnosed by GP testing in the community over a two year period

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The Norfolk Community attributed Clostridium difficile cases

• 199 county residents who had samples submitted by a GP and tested positive for C.difficile between 2010-2012

• 78 had been admitted at least once to Hospital A• 40 had been admitted at least once to Hospital B• No cases had been admitted to both hospitals

• 26 cases had been to Care Homes with at least one other resident case

10 Space-Time Relations of Clostridium difficile cases within a health economy: A Social Network Analysis

Social Network Analysis (SNA)

11 Space-Time Relations of Clostridium difficile cases within a health economy: A Social Network Analysis

• The methods have their roots in the work of 18th Century mathematicians on Graph Theory

• Focuses on relationships between individuals rather than their attributes

• Applied in a wide variety of scientific research –

e.g. genetics, linguistics, electrical engineering, sociology

• Advances in computing power and availability of software have made it easier to apply SNA to a wide range of problems outside of formal research

Data & Software

12 Space-Time Relations of Clostridium difficile cases within a health economy: A Social Network Analysis

PatientID Location Start Date End Date 1st Positive Specimen Date

• Very simple dataset – Just 5 data fields, captured in Excel:

Procedures written in SQL Server to

a) detect space-time coincidences between people in the cohortb) Measure time spent at risk of infection

Co-locationof people

C.diffiicile status not considered

85 of 199 people did spend some time together

…in 2 hospitals, and in 5 care homes

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Hospital A

Hospital B

CARE HOME

CARE HOME

CARE HOMES:

A

CH

CH + B

B

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Hospital A – Taking C.difficile status into consideration – Who was at risk?

Arrow direction represents possible transmission

Arrow size is indicative of Number of Days at Risk

Hospital A – Who spent time with who?

Positive specimens not taken into account

Joining lines represent co-location for 1 or more days CARE

HOME

15 Space-Time Relations of Clostridium difficile cases within a health economy: A Social Network Analysis

Conclusions • Most community diagnosed Clostridium difficile infections

had space time overlaps with earlier onset cases at their local hospital

• The “72 hour rule” of attributing cases to community acquisition denies the centrality of hospital transmission

• Higher levels of infection control are still urgently needed in hospitals to contain the continuing risk of Clostridium difficile

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AcknowledgementsAlongside my co-authors I’d like to acknowledge the contributions of

The Norfolk Health System HCAI Group, and Mr. Steven Martin of Cambridge Institute of Public Health