Antimicrobial Resistance and Current Alternatives in Veterinary Practice: A Review

Antibiotics are commonly used to treat bacterial infections. For many years, antibiotics have been used at sub-therapeutic doses to promote animal growth and misused as prophylactics and metaphylactic on farms. The widespread and improper use of antibiotics has resulted in a serious problem, defined as antibiotic resistance by the World Health Organisation, which is a major public health threat in the 21st century. Bacteria have evolved sophisticated mechanistic strategies to avoid being killed by antibiotics. These strategies can be classified as intrinsic resistance (referring to the inherent structural or functional characteristics of a bacterial species) or acquired resistance (referring to mutations in chromosomal genes or the acquisition of external genetic determinants of resistance). In farm animals, the use of antibiotics warrants serious consideration, as their residues leach into the environment through effluents and come into contact with humans through food. Several factors have contributed to the emergence of antibiotic-resistant bacteria. This review provides an update on antibiotic resistance mechanisms, while focusing on the effects of this threat on veterinary medicine, and highlighting causal factors in clinical practice. Finally, it makes an excursus on alternative therapies, such as the use of bacteriophages, bacteriocins, antimicrobial photodynamic therapy, phytochemicals, and ozone therapy, which should be used to combat antibiotic-resistant infections. Some of these therapies, such as ozone therapy, are aimed at preventing the persistence of antibiotics in animal tissues and their contact with the final consumer of food of animal origin.