Luke T Daum: While working at the Air Force Institute for Operational Health (AFIOH) as a molecular biologist, I witnessed and recognised the critical need to improve the process of sample collection, to be more in line with the rapidly evolving field of molecular diagnostics. Most laboratories collected respiratory samples (such as nasal washings and throat swabs) in a commercial viral transport medium (VTM) designed to maintain microbial viability, manufactured by Remel, Copan and BD. However, reagents in VTMs are actually proven to inhibit downstream PCR. If even small percentages of these compounds are carried over into the PCR, signal can be reduced or lost, so the need for a true molecular transport medium (MTM) was clear.
PS-MTM solves all of these problems. It was specifically developed and optimised for molecular methods such as real-time PCR and next-generation sequencing (NGS). PS-MTM disrupts and shears lipid membranes, inactivates cellular nucleases, and preserves the released RNA and DNA at ambient temperature or above for extended periods. The nucleic acids from samples collected in PS-MTM do not require a cold chain, and microbes are safely inactive for shipping and transport using standard delivery.
Longhorn Vaccines and Diagnostics was established to develop products to impact a future influenza pandemic. New strains of influenza often circulate in remote parts of the world prior to spreading. The US Army was one of the first customers of PS-MTM, used in surveillance. In 2009-10, the world faced an H1N1 pandemic, and PS-MTM became the first ever emergency-use-authorised FDA-approved MTM for collection of influenza viruses. A clinical study demonstrated that PS-MTM was an effective component in real-time PCR detection of symptomatic and presymptomatic influenza infection.
Our initial PS-MTM killing data included independent testing performed at Bioreliance Corporation in Rockville, Maryland. In these studies, PS-MTM was subjected to an FDA-certified USP 32-NF 27 Antimicrobial Effectiveness Testing panel. The study demonstrated high-titer killing of Gram-negative and positive bacteria, and several fungal species, with independent testing undertaken by Battelle Biomedical Research Center in Columbus, Ohio.
The scope of PS-MTM killing was later expanded to include the heartier Gram-positive MTB, with independent killing testing performed by Battelle and the University of Pretoria in South Africa.
PS-MTM is a practical solution for the problems associated with MTB sample collection and transportation. A specialised flocked swab (PrimeSwab) with a load volume of around 100µL is swirled five times in sputum in collection cups and placed in PS-MTM tubes, which can then be transported without cold-chain and infectious disease shipping disclosure to regional or centralised molecular testing and NGS facilities. This means accurate analysis, resulting in more precise personalised treatments for individual patients.
Small volumes of clinical material collected and archived in PS-MTM can be used for subsequent real-time PCR confirmatory tests or drug resistance profiling using NGS. Importantly, the opportunity to detect mutations that confer resistance to key antibiotics provides important information to improve patient care, track MTB and other drug resistance, and facilitate patient selection for new drug development.