Resistance mechanisms to β-lactam antibiotics are briefly presented, emphasizing the importance of extended spectrum β-lactamases. In two independent research works from our laboratories, ESBLs were not detected among Salmonella enterica serovar Enteritidis and resistance to ampicillin was quite low (out of 878 isolates included in the study, 2.2% were resistant to AMP). As food producing animals are reservoirs of ESBL producing bacteria, antibiotic treatment in veterinary practice has to be selective and the prudent use of antimicrobials is strongly recommended.