Antibacterial resistance: an emerging ‘zoonosis’?

Abstract

Antibacterial resistance is a worldwide threat, and concerns have arisen about the involvement of animal commensal and pathogenic bacteria in the maintenance and spread of resistance genes. However, beyond the facts related to the occurrence of resistant microorganisms in food, food-producing animals and companion animals and their transmission to humans, it is important to consider the vast environmental ‘resistome’, the selective pathways underlying the emergence of antibacterial resistance and how we can prepare answers for tomorrow.

Keywords::

• antibacterial resistance
• antibiotics
• companion animal
• food
• livestock
• resistome
• veterinary medicine
• zoonosis

Acknowledgements

The authors are indebted to J Acar for fruitful comments and criticisms.

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Antibacterial resistance is a worldwide threat, and concerns have arisen about the involvement of animal commensal and pathogenic bacteria in the maintenance and spread of resistance genes.

• Salmonella and Campylobacter are the most common pathogens involved in foodborne infections and antimicrobial resistance is detected commonly in isolates from human cases, food-producing animals and food, with 28.9% of isolates being MDR in Europe.

• Other important issues of livestock reservoirs for resistant bacteria concern methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum β-lactamase (ESBL)-producing organisms and enterococci.

• With regards to zoonoses, resistance has emerged in Listeria spp., Brucella spp. and Y. pestis.

• Resistant bacteria are also detected in companion animals: methicillin-resistant and MDR staphylococci, and ESBL, carbapenemase and AMPc-producing Enterobacteriaceae are increasing in veterinary practice and are frequently associated with empiric therapeutic failures.

• Transmission of resistant bacteria from colonized livestock and companion animals to humans has been acknowledged, but serious invasive infections are rarely documented.

• The use of antibiotics as growth promoter (AGP) in food animals and their therapeutic consumption (livestock and pets) are the main underlying factors of antibacterial resistance in animals. In Europe, the use of AGP has been banned since 1 January 2006. However, food of animal origin is exported and imported in many countries, a number of which do not have any current restrictions.

• Other risk factors or selective pressures have been identified as heavy metals, biocides and plant-derived products in the environment.

• On the other hand, anthroponotic transfer of resistant bacteria to animals has been demonstrated and ‘synanthropization’, contamination of wild animals in urban areas, is a new environmental reality with serious veterinary epidemiological significance.

• The environment must be considered as a melting pot of antibacterial resistance genes, the ‘resistome’, which exists outside antibiotic contact. The pollution by antibiotics derived from treated animals and humans, waste disposals and pharmaceutical plants, amplifies the emergence of resistant microorganisms, which can easily transfer their mobile genetic elements to human and animal pathogens.

• The emergency of controlling the antibacterial resistance pandemics has led to common efforts in the ‘prudent use of antibiotics’ both in humans and animals. Surveillance programs have also been established to preclude extension of resistance.

• Antibiotic pressure in animals could be reduced by worldwide removal of AGP, and alternative control measures such as bacteriophage treatments, good hygiene, animal welfare and vaccinations.