#FEMSmicroBlog: Which bacteria live on poultry farms?


Since 2014, increasing numbers of animals live on larger farms with decreasing numbers of farmers in Austria. Such high animal density can result in increased bacterial loads within animal houses. The study “Concentrations of mesophilic bacteria in a poultry farm over two fattening periods focusing on the presence of staphylococci and enterococci” in FEMS Microbes gives an overview of the airborne concentrations of mesophilic bacteria in a chicken farm. Doris Haas and Michael Schalli explain for the #FEMSmicroBlog how this study was achieved. #FascinatingMicrobes


Investigating bacteria on poultry farms

Mesophilic bacteria can colonize human and animal bodies as their optimal growth temperature is between 20 and 45°C. Yet, they adapted to different niches, for example, staphylococci live on animals’ skins while enterococci reside in digestive systems. Some species are facultative pathogenic such as Staphylococcus aureus and can also reside in poultry farms.

The air inside large poultry farms harbours many microorganisms that can originate from soil, feed, bedding or from the animals themselves. The number of bacteria in the ambient air seems to depend on many factors such as the time of the year or the farm location. Especially during the fattening period of chicken, the bacterial compositions in animal houses tend to change due to the increasing animal density.

The study Concentrations of mesophilic bacteria in a poultry farm over two fattening periods focusing on the presence of staphylococci and enterococci” in FEMS Microbes examined the bacterial load of a 28 m2 poultry house in the Austrian province of Styria in a rural mountain region. The aim was to investigate how the number of air-borne mesophilic bacteria, in particular pathogenic species, changes during the fattening period on a farm with a closed housing system and forced ventilation.

Poultry farm investigated in this study for the existence of mesophilic bacteria
Poultry farm investigated in this study. Photo credit: Kropsch.

In total, 420 one-day-old Ross chicken were installed from one breeding’s supplier in two fattening periods of 30 days: one from November to December and the other one from February to March. Air samples were collected using sterile all-glass impinger bottles filled with collection liquid in the centre of the poultry house. Additionally, swab samples were taken from the skins of randomly selected chicken during the fattening periods.


Mesophilic bacteria live in poultry farms

The study found that the highest concentration of total mesophilic bacteria was between 4.9 x 107 and 1.4 x 108 colony forming units per m3 (CFU/m3). In general, poultry houses are presumed to be heavily contaminated by staphylococci up to 1.4 x 104 CFU/m3.

However, the total concentration of mesophilic bacteria and the bacterial group Staphylococcus spp. may not depend on the barn capacity. In short fattening periods, chicken increase enormously in size, weight and surface. More skin bacteria can reside on the animals and further spread into the ambient air inside the barn. Hence, the rapid chicken growth can explain the increasing number of total mesophilic bacteria during each fattening period.

The study further looked at the composition of bacterial communities in poultry houses. Initially, Staphylococcus spp. were not detectable, but increased as the weight of the chicken doubled. The number of Enterococcus spp. also increased. In contrast, enterococci concentrations decreased towards the end of both fattening periods.

The results of the present study confirm findings from other researchers regarding similar species. As one multi-resistance bacterium of high interest, methicillin-resistant Staphylococcus aureus strains were neither detected in the air nor on the skins of chicken.

Together, this bioaerosol investigation shows that the concentration of microbial loads depends on the age and weight of the chicken but not on the number of animals held in a barn.


About the authors of this blog

Priv.- Doz. Dr. Doris Haas is a member of the working team “Applied hygiene and aerobiology” at the D&R Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Austria. She is specialized in the field of bioaerosols; focusing on measurements of particulate matter, airborne fungi and bacteria indoors and in the ambient air. In addition, she is conducting emission measurements in the area of animal farms in different regions in Styria.

Dr. Michael Schalli is working at the Department for Water-Hygiene and Micro-Ecology at the D&R Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Austria. He has worked on the development of carbohydrate derivatives for the treatment of GM1-gangliosidosis. Currently, he is involved in projects concerning aerobiology and the microbiome of water.

About this blog section

The section #FascinatingMicrobes for the #FEMSmicroBlog explains the science behind a paper and highlights the significance and broader context of a recent finding. One of the main goals is to share the fascinating spectrum of microbes across all fields of microbiology.

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