During the past recent years, Enterobacteriaceae have supplanted Gram-positives in terms of frequent resistant bacteria seen in the outpatent setting. This change involves common opportunistic pathogens such as E. coli and K. pneumoniae. It is mainly due to the appearance and dissemination of extended-spectrum beta-lactamases (ESBL), that hydrolyse penicillins and cephalosporins. Bacteria producing these enzymes are often also resistant to quinolones and trimethoprime-sulfamethoxazole. This article, illustrated by a clinical case, presents the current epidemiology of ESBL-producing Enterobacteriaceae and the possible prevention measures and treatment options to fight the growing number of infections that they are causing.