Broad-spectrum β-lactamases among Enterobacteriaceae of animal origin: molecular aspects, mobility and impact on public health

Broad-spectrum ß-lactamase genes (coding for extended-spectrum ß-lactamases and AmpC ß-lactamases) have been frequently demonstrated in the microbiota of food-producing animals. This may pose a human health hazard as these genes may be present in zoonotic bacteria, which would cause a direct problem. They can also be present in commensals, which may act as a reservoir of resistance genes for pathogens causing disease both in humans and in animals. Broad-spectrum ß-lactamase genes are frequently located on mobile genetic elements, such as plasmids, transposons and integrons, which often also carry additional resistance genes. This could limit treatment options for infections caused by broad-spectrum ß-lactam-resistant microorganisms. This review addresses the growing burden of broad-spectrum ß-lactam resistance among Enterobacteriaceae isolated from food, companion and wild animals worldwide. To explore the human health hazard, the diversity of broad-spectrum ß-lactamases among Enterobacteriaceae derived from animals is compared with respect to their presence in human bacteria. Furthermore, the possibilities of the exchange of genes encoding broad-spectrum ß-lactamases - including the exchange of the transposons and plasmids that serve as vehicles for these genes - between different ecosystems (human and animal) are discussed.