An overview of extended-spectrum beta-lactamases in veterinary medicine and their public health consequences.

Serious human and animal infections caused by bacteria are usually treated with beta-lactams. Extended-spectrum beta-lactamases (ESBLs) constitute the most clinically and economically important enzymes that are able to hydrolyze and inactivate beta-lactam antibiotics in veterinary medicine. The spread of ESBLs represents a serious threat to healthcare systems, drastically undermining therapeutic options. The relationship between drug usage and the emergence of resistance has been extensively reported. Nevertheless, the use of antimicrobials in veterinary medicine and the emergence of ESBLs in animals remains a matter of debate. Moreover, there is still controversy about whether antibiotic usage in farm animals poses a potential public health risk. This review will (i) deal with aspects related to the presence of ESBLs in veterinary medicine, (ii) its link with human medicine, and (iii) discuss strategies to be implemented to preserve antimicrobial effectiveness. New insights relative to old questions concerning antimicrobial use in domestic animals are also presented.