Extended spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae were first reported in Europe in the 1980s and have since become a worldwide problem. This has resulted in increased morbidity, mortality and cost in treating the infections they cause (Paterson et al, 2001; Bisson et al, 2002). In the UK the prevalence of ESBL rose from 5.4% in 1997 to 22.7% in 1999 (Goossens, 2000). ESBL are not the only ß-lactamases to present resistance to 1st, 2nd and 3rd generation cephalosporins but are the most important. New strains produce a particular type of ESBL, the CTX-M type, which is able to break down a wider range of antibiotics. These strains were unrecorded in the UK prior to 2000. They have spread rapidly since 2003, causing infections such as urinary tract infections (UTIs) in hospital patients as well as those treated in the community (Livermore and Woodford, 2004). Enterobacteriaceae are a well-known cause of healthcareassociated infection (HAI). Their antimicrobial resistance is commonly caused by the production of ß-lactamases, therefore this article discusses methods used to limit the emergence of ESBL producing strains and to prevent the spread of those already present.