Preliminary Validation of a Method Combining Cultivation and Cloning-Based Approaches to Monitor Airborne Bacteria

It is already known that occupational exposure to bioaerosols or organic dust could be harmful for occupants, but mostly the correlation to occurring bacteria is missing. Especially, cultivation of bacteria from bioaerosols is important to get an insight on occurring and possibly infectious bacteria. These measures are highly time consuming and cost intensive. Therefore, to monitor bacterial diversity in bioaerosol samples and to avoid isolation procedures, an approach was applied using a combination of cultivation and cloning-based approach. Preliminary validation of the method was determined using 11 different bacterial strains. After DNA extraction and 16S rRNA gene amplification of grown colonies, subsequent cloning and sequencing was conducted. Initially, to figure out a suitable DNA extraction method, applicable for different airborne bacteria, four DNA extraction protocols were compared. Significantly, best results were determined using the FAST DNA®Spin Kit for Soil with respect to DNA quantity and quality of bacterial cultures. Cloning approach from a mixture of amplified 16S rRNA genes of 11 isolates and following sequence data analysis shows a recovery of all strains when five clones per bacterial strain were analysed. The results clearly demonstrate that a combination of cultivation-based approaches and cloning processes can simplify bioaerosol monitoring of viable and probably infectious bacteria. The implementation of the present method into practice allows a simple and preventive investigation of bioaerosols at work places.