Internally controlled PCR system for detection of airborne microorganisms

Recently, we reported the outcomes of feasibility studies of a technological approach allowing rapid detection of a wide range of bioaerosols by combining a personal bioaerosol sampler with a real-time PCR technology. The protocol was found suitable for detection of targeted microorganisms within relatively short time periods. Considering the crucial importance of the PCR procedure quality control, the current paper reports the results of the development of an internally controlled PCR system for utilization by the above technology. The suggested strategy is based on utilization of only two fluorescent dyes, which are used respectively for target and internal amplification control (IAC) DNA amplification. A bacteriophage T4 and recombinant phage fd (M13) were used in this research as target and IAC, respectively. The constructed IAC was added directly to the collection liquid of the personal bioaerosol sampler enabling quality control to be present throughout the entire sampling-analysis procedures. For performance evaluation, serial ten-fold dilutions of T4 phage were aerosolized and sampled over a 10 minutes time period. The results showed that T4 phage could be reliably detected at the concentration of around 200 PFU per litre of air over the 10 minutes sampling period. The developed PCR assay demonstrated high specificity and no cross reaction. It is concluded that the recombinant phage fd is suitable for utilization as an internal control enabling to significantly minimize false negative results for bioaerosol detection procedures.