title: Normalization of test and evaluation of biothreat detection systems: overcoming microbial air content fluctuations by using a standardized reagent bacterial mixture.
abstract: Test and evaluation of engineered biothreat agent detection systems ("biodetectors") are a challenging task for government agencies and industries involved in biosecurity and biodefense programs. In addition to user friendly features, biodetectors need to perform both highly sensitive and specific detection, and must not produce excessive false alerts. In fact, the atmosphere displays a number of variables such as airborne bacterial content that can interfere with the detection process, thus impeding comparative tests when carried out at different times or places. To overcome these bacterial air content fluctuations, a standardized reagent bacterial mixture (SRBM), consisting in a collection of selected cultivable environmental species that are prevalent in temperate climate bioaerosols, was designed to generate a stable, reproducible, and easy to use surrogate of bioaerosol sample. The rationale, design, and production process are reported. The results showed that 8.59; CI 95%: 8.46-8.72 log cfu distributed into vials underwent a 0.95; CI 95%: 0.65-1.26 log viability decay after dehydration and subsequent reconstitution, thus advantageously mimicking a natural bioaerosol sample which is typically composed of cultivable and uncultivable particles. Dehydrated SRBM was stable for more than 12months at 4°C and allowed the reconstitution of a dead/live cells aqueous suspension that is stable for 96h at +4°C, according to plate counts. Specific detection of a simulating biothreat agent (e.g. Bacillus atrophaeus) by immuno-magnetic or PCR assays did not display any significant loss of sensitivity, false negative or positive results in the presence of SRBM. This work provides guidance on testing and evaluating detection devices, and may contribute to the establishment of suitable standards and normalized procedures.
authors.affiliation: DGA Maîtrise NRBC, Le Bouchet-B.P. no 3, 91710 Vert-le-Petit, France. Electronic address: laurent.berchebru@intradef.gouv.fr.
authors.forename: Laurent
authors.initials: L
authors.lastname: Berchebru
authors.affiliation: DGA Maîtrise NRBC, Le Bouchet-B.P. no 3, 91710 Vert-le-Petit, France. Electronic address: pascal.rameil@intradef.gouv.fr.
authors.forename: Pascal
authors.initials: P
authors.lastname: Rameil
authors.affiliation: DGA Maîtrise NRBC, Le Bouchet-B.P. no 3, 91710 Vert-le-Petit, France. Electronic address: jean-christophe.gaudin@intradef.gouv.fr.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Gaudin
authors.affiliation: DGA Maîtrise NRBC, Le Bouchet-B.P. no 3, 91710 Vert-le-Petit, France. Electronic address: sabrina.gausson@intradef.gouv.fr.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Gausson
authors.affiliation: DGA Maîtrise NRBC, Le Bouchet-B.P. no 3, 91710 Vert-le-Petit, France. Electronic address: guilhem.larigauderie@intradef.gouv.fr.
authors.forename: Guilhem
authors.initials: G
authors.lastname: Larigauderie
authors.affiliation: DGA Maîtrise NRBC, Le Bouchet-B.P. no 3, 91710 Vert-le-Petit, France. Electronic address: celine.pujol@intradef.gouv.fr.
authors.forename: Céline
authors.initials: C
authors.lastname: Pujol
authors.affiliation: DGA Maîtrise NRBC, Le Bouchet-B.P. no 3, 91710 Vert-le-Petit, France. Electronic address: yannick.morel@intradef.gouv.fr.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Morel
authors.affiliation: DGA Maîtrise NRBC, Le Bouchet-B.P. no 3, 91710 Vert-le-Petit, France. Electronic address: vincent.ramisse@intradef.gouv.fr.
authors.forename: Vincent
authors.initials: V
authors.lastname: Ramisse
mesh_terms: D000336:Aerosols; D000391:Air Microbiology; D001419:Bacteria / Q000302:isolation & purification*; D015374:Biosensing Techniques / Q000379:methods* / Q000592:standards*; D006801:Humans; D050296:Microbial Viability; D012015:Reference Standards; D013696:Temperature
chemical_list: D000336:Aerosols
keywords: Aerosol; Biological detection; Bioterrorism; Evaluation