Background:
There is a paucity of information about the actual causes and relative prevalence of GIT pathogens resulting in hospitalisation in the Australian setting. It is believed that gastrointestinal illnesses contribute a significant burden to the health system, therefore knowing the actual causes and their prevalence is important, to inform prompt diagnosis and treatment, to prevent complications and reduce the burden on the health care system.

Methods:
A retrospective cross-sectional survey of laboratory and clinical records for patients with gastrointestinal symptoms, and had an enteric organism detected in their stools and were seen at four major public hospitals in Sydney, from January 2007 to December 2010 was conducted.

Results:
Gastrointestinal illnesses (GIT) are caused by several pathogens, which varies between older children/adults and children. Children 0-5 years old were mainly affected by rotavirus (22.4%), norovirus (19.6%), and adenovirus (17.5%). Campylobacter (57.5%) and Salmonella spp, (51.9%) were frequently diagnosed in persons age 6-59 years old (P<0.001), while Clostridium difficile (57.3%), was more frequently diagnosed in persons 60 years and older. Infections with Blastocystis spp increased with increasing age (P<0.001), and the incidence of G. intestinalis was highest in persons under 13 years (P=0.018). The risk for infection with C. difficile was associated with prolonged antibiotic therapy (OR 6.3; P<0.001), recent surgery (OR 2.2; P=0.030), and chronic GIT illness (OR 2.4; P= 0.035). Seasonal variations in illnesses were observed.

Conclusion:
This study is the largest hospital based study to incorporate data from multiple sites to describe the epidemiology of infectious GIT illnesses in NSW State in the last 20 years. It emphasises the importance of laboratory diagnosis of enteric infections and highlights the need for better data collection in hospital settings to better understand and manage disease risk factors in the community.