Surface sampling and transport for an effective microbial forensics: recovery of bacterial nucleic acid and protein...

Microbial forensic analysis for deliberate, accidental and natural release of pathogens entail serious ramifications on human health. Surface sampling and transport for downstream verification of biological agents is posed with challenges including presence of background microbial consortium, delay in transport from remote location, and vulnerability of biomolecules to compromised cold chain. Glass surface pre-exposed to field conditions was spiked with S. typhi and sampled with swab. Storage of swab in VTM, PBS, alkaline lysis buffer, and under desiccated condition at RT and 10 °C for a period of 3 days indicated significantly higher DNA recovery for swabs stored under desiccated conditions. Recovery of bacterial protein from three transport media indicated pronounced stability at both temperatures. Tape-lift was envisaged as the method of surface sampling for providing stability to analytes during transport. Post-spiking (S. typhi) incubation of adhesive tapes for 3 and 7 days at RT indicated DNA recovery on both the time points and extracted DNA was amenable to PCR amplification of target specific gene. Methodology was also optimized for recovery of bacterial protein from adhesive tapes using S. typhi and B. anthracis Sterne spores. Protein stability was observed for both the agents after 3 and 7 days of storage at RT. The proteins extracted from the spiked adhesive tapes could be successfully identified using high resolution mass spectrometry (HRMS) with significant proteome coverage (84% on 3 d and 60% on 7 d). Application of adhesive tapes for sampling smooth surfaces for extraction of bacterial nucleic acid and protein suggest stability of analytes even without cold chain.