title: Observing bacterial activity interferometrically.
abstract: It is shown that bacterial activity, even of slowly growing species, can be detected by precise interferometric measurements of refractive index changes of the culture medium. The bacteria-containing sample is kept in an isothermal block together with a reference liquid without bacteria. The biological activity is obtained from the difference of the index changes of these samples. Experiments were performed with Bacilo Calmette-Guérin. The order of magnitude of the observed total refractive index change was compatible with theoretical estimates based on the amount of available oxygen. An unexpected positive index change during the lag phase was observed, which might permit fast diagnostics in medical applications. This technique may provide cheap and quick tests of bacterial susceptibility with respect to antibiotics.
authors.affiliation: Departamento de Física, ICE, Universidade Federal de Juiz de Fora, 360 36 330 Juiz de Fora, MG, Brazil.
authors.forename: D Faragó
authors.initials: DF
authors.lastname: Jardim
authors.forename: R Batista
authors.initials: RB
authors.lastname: Santiago Neto
authors.forename: R R P
authors.initials: RR
authors.lastname: Machado
authors.forename: F M
authors.initials: FM
authors.lastname: Aarestrup
authors.forename: J P R F
authors.initials: JP
authors.lastname: de Mendonça
authors.forename: B
authors.initials: B
authors.lastname: Lesche
mesh_terms: D007368:Interferometry / Q000379:methods*; D008826:Microbial Sensitivity Tests / Q000379:methods*; D009163:Mycobacterium bovis / Q000254:growth & development / Q000302:isolation & purification* / Q000378:metabolism*