Bioaerosols: An underestimated vector for the dissemination of antibiotic resistance in broiler chicken farms

Authors: Joanie Lemieux, Antony Vincent, Ève Bérubé, Marthe Bernier, Meredith Elizabeth Gill, Luc Trudel, Nathalie Turgeon, Maurice Boissinot, Frédéric Raymond and Caroline Duchaine

Departments and institutes associated with the authors:

1. Département de biochimie, microbiologie et bio-informatique, Faculté des sciences et de génie, Université Laval

2. Centre de recherche de l’Institut de cardiologie et pneumologie de Québec, Université Laval

3. Département des sciences animales, Faculté des sciences de l’agriculture et de l’alimentation, Université Laval

4. Centre de recherche en infectiologie de l’Université Laval, axe maladies infectieuses et immunitaires, Centre de recherche du CHU de Québec, Université Laval

5. Institut sur la nutrition et les aliments fonctionnels, Université Laval

6. Chaire de recherche du Canada sur les bioaérosols

Article published in Nouvailes, September 2024, Volume 28, Pages 38 to 41

In Canada, nearly 80% of antibiotics distributed in the country are used for livestock production. These antibiotics are mainly administered to animals to prevent and treat infections. The use of these antibiotics accelerates the natural phenomenon of antibiotic resistance (AR), promotes the emergence of antibiotic-resistant bacteria (ARB) and the transmission of their resistance genes (ARG). The Éleveurs de volailles du Québec have been proactive about AR by deciding to reduce the use of antibiotics and even to no longer use certain categories of antibiotics.

Bioaerosols

Farms, such as broiler chicken farms, are major emitters of bioaerosols. Bioaerosols are heterogeneous biological particles suspended in the air that may contain microorganisms, including BRA. The main sources of bioaerosols in a poultry house are chickens (skin, feathers and droppings), litter and feed.

Once suspended in the indoor air of a poultry house, a bioaerosol has the potential to be emitted outside via fans that push air out of the building.

Once outside, the fate of bioaerosols depends on several factors such as their size as well as wind speed and direction. These factors influence the distance they can travel, ranging from meters to several kilometers. Therefore, a bioaerosol containing one or more BRAs can be a vehicle for spreading AR to other environments, close to livestock and human activities.

This research focuses, in part, on the profile of viable BRAs present in the indoor air of broiler chicken coops, and allows for a comparison of conventional production with that without antibiotics. Productions that use antibiotics are called conventional farms, while some productions that choose not to administer antibiotics are called "antibiotic-free".

Methodology

A bacterial viability air sampler collects bioaerosols from the indoor air of four poultry houses, two conventional and two without antibiotics. The air samples containing the bioaerosols are then applied to culture media containing antibiotics. The resistant bacteria that have multiplied in the presence of antibiotics are isolated and analyzed in detail to identify which GRAs are encoded in their genetic material.

Preliminary findings

The comparison between conventional and antibiotic-free farms will allow us to know if there is a difference in the profile of ARGs that could be associated with the administration or not of antibiotics. Not all ARGs are problematic. Those considered critical are those that are found in circulation in the population, human and animal, since they can cause difficulties in the treatment of certain infections.

The presence of BRA in the air of broiler chicken houses raised without antibiotics is not surprising. BRA are present in all environments, starting with the intestines of animals and humans. It is possible that chicks arriving in the farms for fattening are already carriers of BRA and GRA. Also, the environment of the poultry house (litter, water, feed) is not free of BRA and can contribute to enriching the profile of the GRA identified.

The results of this research will be crucial as they open the dialogue on the need to implement methods to control bioaerosol sources and to create tools to monitor the air inside and outside livestock farms. The ability of some bioaerosols to transport BRA and their GRA, from inside to outside and over variable distances, poses a potential risk to public health and surrounding ecosystems.

To mitigate the risks associated with the spread of ARBs, several measures are recommended:

1. Air quality monitoring.

Set up regular monitoring systems to detect the presence of ARBs in indoor air as well as in the air near livestock farms.

2. Best management practices in livestock farms.

Review management protocols to minimize the production and dispersion of bioaerosols containing ARBs, for example by reducing dust or by biofiltrating the air leaving exhaust fans.

3. Reduce the use of antibiotics.

Encourage the prudent and targeted use of antibiotics in livestock farming and adopt alternatives to antibiotics to combat animal diseases. Joanie Lemieux adds that chicks are probably carriers of GRA that do not come from the breeding environment, but potentially transmitted by the layer during egg formation and then in the incubator environment. In addition, raising chicks without antibiotics does not prevent the presence of certain BRA and their GRA.

The results of this research open the dialogue on the need to implement methods for controlling sources of bioaerosols and to create tools for monitoring the air inside and outside livestock farms.

These measures are essential to protect public health, animal health and the environment. It is imperative that livestock producers, researchers and policy makers work together to implement these recommendations and prevent health crises. These integrated actions are part of the World Health Organization’s “One Health” approach, because the health of humans, animals and ecosystems are closely linked.