A National Estimate of the Health and Cost Burden of Escherichia coli Bacteraemia in the Hospital Setting: The Importance of Antibiotic Resistance

Background: Antibiotic resistance poses a threat to public health and a burden to healthcare systems. Escherichia coli causes more bacteraemia cases in England than any other bacterial species, these infections, in part due to their high incidence, also pose a significant antibiotic resistance burden. The main aim of this study was to estimate the impact of E. coli bacteraemia on patient in-hospital mortality and length of stay. Secondarily, this study also aimed to estimate the effect of antibiotic resistance on these outcomes. Methods and Findings: Case patients were adult E. coli bacteraemia patients infected between July 2011 and June 2012, as reported in an English national mandatory surveillance database, with susceptibility data taken from a national laboratory surveillance database. Control patients were all non-case, adult patients with an English hospital admission record. Case and control patient characteristics and admission information were taken from NHS Digital Datasets. Resistance was defined as non-susceptible and intermediate isolates, whilst susceptible was defined as susceptible and non-tested isolates. Time to in-hospital mortality and discharge was investigated through Cox proportional hazards models. To acquire estimates of excess length of stay, multistate models were constructed, with a unit bed day cost applied to estimate cost burden. The total number of case and control hospital spells was 19,914 and 8,963,011 respectively. Acquisition of E. coli bacteraemia was associated with a statistically significant increased daily risk of in-hospital mortality, especially for the first seven days of hospital admission [hazard ratio = 2.80 (95% confidence interval; 2.66- 2.94)]. Antibiotic resistance did not seem to significantly increase this risk further, though did significantly reduce risk of experiencing a discharge event (dead or alive). E. coli bacteraemia was estimated to cost 20,550,800 GBP (Great British Pounds) over the study period (rounded to the nearest 100 GBP), with resistance associated with excess costs per infection of 180 - 430 GBP dependent on resistance type (rounded to the nearest 10 GBP). Conclusions: E. coli bacteraemia places a significant burden on patient health and on the hospital sector in England. Resistance is an important factor on length of stay with regards to such infections.