The use of carbapenems, very broad spectrum antibiotics of last resort, is becoming more common due to the increased prevalence in the hospital and community of extended spectrum β-lactamase (ESBL) producing gram-negative bacilli (GNB), including CTX-M type, which are resistant to all other β-lactam antibiotics. Meanwhile, it creates a selective pressure towards emergence of strains which are also resistant to carbapenems, placing patients in a catastrophic situation of therapeutic dead-end. A better understanding of the mechanisms of emergence of BGN resistant to carbapenems is necessary to optimize their use and undertake preventive measures to preserve their effectiveness.