Abstract
PurposeThe aim of this study was to characterize the ways of spreading of the most common bacterial species isolated from workers as well as from the air and raw materials at the workplaces in power plant utilizing biomass sources. To monitor microbial transmission and identify the source of contamination in the working environment, a combination of molecular and biochemical methods was applied.MethodsThe study was carried out at workplaces in power plant utilizes biomass as a main fuel source. At each of the studied workplaces, bioaerosol particles were collected on sterile Teflon filters using personal conical inhalable samplers (CIS), and biomass samples (straw pellets and briquettes, corn briquettes, sunflower pellets and wood chips) were directly taken from their storage places. Simultaneously with that, the swab samples from the hands of ten workers and their used respiratory masks (of FFP2 class) were also collected after the work shift to evaluate individual workers’ microbial contamination. In all collected samples, total bacterial concentrations were assessed and the most common microbial isolates were identified to the species level using both biochemical (API tests) and molecular polymerase chain reaction (PCR), followed by random amplification of polymorphic DNA (RAPD) typing methods.ResultsThe mean concentrations of culturable bacteria in the air and in biomass samples at the studied workplaces were high, i.e. 1.2 × 106cfu/m3 and 3.8 × 104cfu/g, respectively. The number of bacteria in the swab and mask samples also reached a high level of 1.4 × 104 cfu/ml and 1.9 × 103 cfu/cm2, respectively. Among the most frequently isolated microorganisms from all types of samples were Gram-positive bacteria of the genus Bacillus and Staphylococcus xylosus. 37 bacterial strains belonging to the genus Bacillus (B. licheniformis 8, B. pumilus 15 and B. subtilis 4) and Staphylococcus (10) were genotyped by the RAPD-PCR method. Based on RAPD-PCR analyses, the genomic similarity among 19 Bacillus strains isolated from biomass, air, protective mask and hand samples as well as 6 S. xylosus strains isolated from air, mask and hand samples exceeded 80%.ConclusionThis study demonstrated that biomass is the primary source of bacteria at power plant workplaces. These results also revealed that biomass-associated bacteria can be easily transferred to workers’ hands and mask during their routine activities. To improve health protection at the workplaces, adequate training courses on hand hygiene and how to use and remove respiratory masks correctly for workers should be introduced as a key element of the prevention strategy. From the occupational point of view, the PCR-based methods seem to be an efficient tool for a fast and precise typing of bacterial strains isolated from different sources in the occupational environment. Such methods may help to implement appropriate prophylactic procedures and minimize transmission of infectious agents at workplaces.
Highlights
It is well known that poor hygiene creates favorable conditions for pathogen transfer in occupational settings
From the occupational point of view, the polymerase chain reaction (PCR)-based methods seem to be an efficient tool for a fast and precise typing of bacterial strains isolated from different sources in the occupational environment
Among all isolated culturable microorganisms, eight bacterial (Actinomyces spp., B. subtilis, Corynebacterium spp., P. mirabilis, S. aureus, S. pyogenes, Streptococcus spp. and Streptomyces spp.) species were classified as risk group 2, according to an Ordinance of the Polish Ministry of Health (2005), and as such may be responsible for adverse health outcomes in exposed individuals
Summary
It is well known that poor hygiene creates favorable conditions for pathogen transfer in occupational settings. Proper environmental control of microbial contamination in the working environment should be based on the identification of high-risk pathogens, and focus on the qualitative characterization of the prevailing microbial communities Such monitoring should allow the detection of infection sources, microbial pathways and control of diversity of individual microbial strains both in the workplace as well as in individual workers. Previous studies have shown that handling and processing of biomass create a risk for workers due to their exposure to harmful bacterial and fungal agents released from this organic source (Ławniczek-Wałczyk et al 2012; Madsen 2006, 2009) This problem still seems to be important and requires broadening of our knowledge regarding the identification of harmful biological agents, their routes of transmission at workplaces as well as the ways to reduce such exposure. There are very few studies concerning environmental transmission of pathogens as well as comparing the relationship between microorganisms isolated from contaminated materials presented in the workplace (e.g. waste, biomass, litter, product) and isolates from the breathing zone of the employee (bioaerosol samples) or from hands of workers (Orsini et al 2002; Rastogi and Sani 2011; Scott 2013; Vela et al 2012; Zeinali et al 2015)
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