The main concern of this chapter is to present mechanism of extended spectrum beta lactam (ESBL) mediated resistance in GNB, modes of transmission, epidemiology, risk factors, and management of infections caused by these pathogens. ESBLs are capable of hydrolyzing penicillins, cephalosporins of the first, second, third and fourth generations, and the monobactam antibiotic aztreonam. ESBLs can be inhibited by b-lactamase inhibitors such as clavulanic acid. ESBL-producing bacteria can be resistant to antibiotics which include quinolones, aminoglycosides and sulfamethoxazole. SHV, TEM and CTX-M are three types of ESBL. Urinary tract infection, bacteremia, respiratory tract infection, gastrointestinal tract infection, skin and soft tissue infection, catheter or device related infection, sinusitis and neurosurgical meningitis are various infections caused by ESBL-producing bacteria. Carbapenems, cephalosporins, cephamycins, beta-lactam with beta-lactamase inhibitors for ESBL infections and automated tests for ESBL detection are treatment of ESBL infections.