Microbial contamination level and microbial diversity of occupational environment in commercial and traditional dairy plants
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Central Institute for Labour Protection – National Research Institute, Warsaw, Poland
Agata Stobnicka-Kupiec   

Central Institute for Labour Protection – National Research Institute, Czerniakowska 16 Street, 00-701, Warsaw, Poland
The aim of this study was to assess microbial contamination of the air and surfaces at workplaces in commercial (CD) and traditional (TD) dairies.

Material and methods:
Bioaerosol (impactor) and surface (swab) samples were collected in CD and in TD. Bacterial and fungal concentrations in the air and on surfaces were calculated and all isolated microorganisms taxonomically identified, based on their morphological, biochemical and molecular features.

Average concentrations of bacterial aerosol ranged between 70–860 CFU/m3 and 265–14639 CFU/m3, while for fungal aerosol were between 50–290 CFU/m3 and 55–480 CFU/m3 in CD and TD, respectively. Average bacterial concentrations on surfaces ranged between 1.0–49.7 CFU/cm2 and 0.2–60.4 CFU/cm2, whereas average fungal surface contamination ranged between 0–2.7 CFU/cm2 and 0–4.6 CFU/cm2 in CD and TD, respectively. Qualitative analysis revealed mainly the presence of saprophytic microorganisms; however, several pathogenic strains (Staphylococcus aureus, Streptococcus intermedius, Clostridium perfringens, Actinomyces spp., Streptomyces spp., Candida albicans) were also isolated from both the air and surface samples in the studied dairies.

The air and surfaces in TD were more polluted than those in CD; however, in both types of dairies, the levels of microbial contaminants did not exceed respective threshold limit values. Nevertheless, the presence of pathogenic microorganisms may increase health risk for dairy workers and influence the quality of products. Hence, proper hygienic measures should be introduced and performed to guarantee high microbial quality of both production processes and milk products.

This study was based on the results of a research project undertaken within the scope of the IV stage of the National Programme ‘Improvement of safety and working conditions’, partly supported in 2017–2019, within the scope of research and development, by the Ministry of Science and Higher Education/National Centre for Research and Development, with the Central Institute for Labour Protection/National Research Institute as main co-ordinator of the programme (Project No. II.N.16). The authors express their thanks all employees of the dairy farms who assisted in the performance and completion of this study.
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