Escherichia coli (E. coli) is the most frequent bacterium implicated in community-acquired infection as well as in nosocomial infections. This bacterium is characterised by numerous possibilities to acquire resistance mechanisms, even during antibiotic treatment. The main mechanism of resistance is the production of beta-lactamines, enzymes hydrolysing beta-lactam ring. This paper describes enzymatic mechanisms of resistance of E. coli to beta-lactam and indicates the necessity of a good knowledge of the risk factors for resistance to have an adapted good clinical practice in using antibiotics.