Community-associated Clostridium diffiicle infection in Western Australia: epidemiology and implications for public health policy

Author: Lauren Bloomfield

Bloomfield, Lauren, 2016 Community-associated Clostridium diffiicle infection in Western Australia: epidemiology and implications for public health policy, Flinders University, School of Health Sciences

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Clostridium difficile is a spore-forming, Gram-positive, anaerobic bacillus, which is capable of causing disease ranging from mild diarrhoea to fulminant colitis and toxic megacolon which can result in death. Rates of C. difficile infection (CDI) have increased in Australia, following significant rises in the rest of the world. Western Australian (WA) rates of hospital-identified CDI (HI-CDI) are reported by the WA Department of Health via Healthcare Infection Surveillance WA (HISWA).

Recent data show a trebling in CDI rates between January 2010 and December 2014. Enhanced surveillance, which involves applying a standard case definition to determine whether an infection is healthcare-associated (HA) or community-associated (CA), is encouraged at WA healthcare facilities (HCFs), although this has not been undertaken broadly to date.

The literature suggests a changing epidemiology of CDI, in which an increase in community cases is being observed, and disease is occurring in individuals who lack any of the classical risk factors: younger adults with no history of antibiotic use or recent hospitalisation. Locally, there has been little work done on establishing the burden of CA-CDI on the healthcare system.

In order to understand the epidemiology of CDI in WA, and further to determine potential risk factors behind this infection in the community, a retrospective review of HI-CDI cases reported to HISWA was conducted. This review of 2,962 cases from metropolitan public hospitals allowed determination of the proportions of HA and CA infection. Further analysis was conducted to establish ribotyping diversity, and to determine potential risk factors in CA cases based on demographic data collected.

There was a higher proportion of CA-CDI in 2014 compared to the baseline year (2010). CA-CDI cases comprised approximately 30% of all HI-CDI, with case numbers of both CA and HA increasing over the study period. CA cases were younger than HA cases, and more likely to be diagnosed at a non-tertiary hospital. These findings are in keeping with the international literature. A significantly higher proportion of CA-CDI in females aged 20 – 39 was a key finding, warranting further investigation. Analysis of prominent ribotypes showed the UK 014/020 group was the most common strain among both CA and HA cases, accounting for 28.3% of all ribotyped cases. There was a significantly higher diversity of ribotypes among HA cases which suggests that imported cases from the community may be an important contributor to the overall burden of disease detected among inpatients.

Ribotyping data also identified the emergence of UK 012 –a seldom-isolated strain in WA prior to 2013; cases of this ribotype increased over the study period to become the second most prevalent strain in 2014. Although this strain did not cause severe disease, its appearance highlights the potential for one ribotype to rapidly emerge and dominate within a region.

In conclusion, CA-CDI represents a substantial proportion of CDI cases diagnosed in WA hospitals. Further work is required to determine the drivers behind disease acquired outside of hospitals, including investigation of food, animal and environmental sources. Improving our understanding of this infection in the community is essential in determining appropriate measures to control the spread of disease and protect the community from this increasing public health threat.

Keywords: Clostridium difficile, community-associated, Western Australia

Subject: Public Health thesis

Thesis type: Professional Doctorate
Completed: 2016
School: School of Health Sciences
Supervisor: Professor Paul Ward