title: Application of the quartz crystal microbalance to the monitoring of Staphylococcus epidermidis antigen-antibody agglutination.
abstract: The change in solution properties due to the agglutination of an antigen with its specific antibody has previously been used as a marker of infection. This method has been modified to allow the binding activity between species to be followed using the frequency response of a quartz crystal microbalance (QCM). The Bayston agglutination plate assay for Staphylococcus epidermidis has been modified to allow the electrode of a QCM to act as a direct sensor for the change in solution properties as agglutination occurs. Antibody and antigen were introduced to the crystal surface and the agglutination process was followed as a change in crystal resonant frequency. Serum, known to be infected with the organism, gave a titre of 3.9x10(-2)% v/v (-118 Hz, +/-12 SD, N = 9) matching that given by triplicate plate assay. Uninfected serum gave no frequency changes at this concentration, yielding a titre of 2.5x10(-2)% v/v again matching the plate titre (N = 3). Infected serum gave responses 40 times faster then those of the uninfected serum. The piezoelectric quartz crystal method gave a positive or negative diagnosis in <15 min compared with the 24 h required for the plate assay.
authors.affiliation: Novel Methods Group, CASS, Smithkline Beecham Pharmaceuticals, Harlow, Essex, UK. karl_d_pavey@sbphrd.com
authors.forename: K D
authors.initials: KD
authors.lastname: Pavey
authors.forename: Z
authors.initials: Z
authors.lastname: Ali
authors.forename: C J
authors.initials: CJ
authors.lastname: Olliff
authors.forename: F
authors.initials: F
authors.lastname: Paul
mesh_terms: D000372:Agglutination Tests; D000818:Animals; D000907:Antibodies, Bacterial / Q000032:analysis*; D000942:Antigens, Bacterial / Q000032:analysis* / Q000097:blood; D006801:Humans; D011791:Quartz; D011817:Rabbits; D015203:Reproducibility of Results; D013212:Staphylococcus epidermidis / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D011791:Quartz