Speeding up E. coli identification

Escherichia coli belongs to the family of enteric bacteria called the Enterobacteriaceae, and is a common inhabitant of the gastrointestinal tract in humans and animals. Although E. coli is a normal colonist of the gut, occasionally it is associated with human disease. This can be due to infections of the intestine resulting from ingestion of a pathogenic strain of E. coli, such as E. coli O157 or E. coli O104 (the serogroup responsible for the recent outbreak of haemolytic uraemic syndrome in Germany1) causing diarrhoea and related diseases, or it can be due to the opportunistic infection of sites outside the gastrointestinal tract by E. coli originating from the gut. The most common E. coli infections outside of the gastrointestinal tract are urinary tract infections (UTIs). For example, E. coli is the most common cause of cystitis. This disease can affect otherwise healthy individuals in the community, but it is also frequently associated with urinary catheterisation in hospitalised patients. Occasionally, E. coli infection can ascend the urinary tract to the kidneys, causing pyelonephritis.2 Escherichia coli can also cause intraabdominal infections following leakage of the contents of the gut into the abdomen, for example as a result of a ruptured appendix, perforated ulcer or traumatic injury to the abdomen.2 On rare occasions, E. coli can spread from the primary site of infection into the bloodstream, resulting in bacteraemia. This can cause patients to become severely ill with clinical signs of sepsis. Along with Staphylococcus aureus, E. coli is one of the most frequent causes of bacteraemia.2 Those particularly at risk of infection are the elderly and the immunocompromised. Recurrence of E. coli bacteraemia, due to relapse or reinfection, is not uncommon.3 Risk factors for this phenomenon have been identified as immunosuppression, urinary biliary obstruction, chronic liver disease and the presence of a central venous catheter.3

Mandatory surveillance

Following advice from the Advisory Committee on Antimicrobial Resistance and Healthcare Associated Infections (ARHAI), the Department of Health has recently introduced mandatory surveillance of E. coli bacteraemias in June 2011.4,5 This action comes as no surprise, having been eluded to by Health Secretary Andrew Lansley in October last year,6 and is in response to the continued annual increase of E. coli infections being reported via the voluntary surveillance system,7 in contrast to the falling rates of MRSA and C. difficile infections. In England, Wales and Northern Ireland, there has been a 35% increase in E. coli bacteraemias reported since 2006 (Fig. 1), compared with a 0.2% increase for all bacteraemias.7 There is no evidence that this is a result of increased ascertainment. Although many reported E. coli bacteraemias appear to originate in the community – up to 70% in a recent retrospective study undertaken by the Health Protection Agency (HPA) – a proportion of these patients may have had a recent history of hospitalisation – 39% in the retrospective study.8 A recent HPA report stated: “The factors underlying this increase (of E. coli bacteraemias) are poorly understood, and the primary purpose of the enhanced surveillance is to gather clinical and demographic data that will enhance understanding of the pathogenesis and epidemiology of the infection. This information will allow more accurate determination of possible interventions to prevent avoidable bacteraemias.”