The ability of direct fluorescence-based, two-colour assays to detect different physiological states of oral streptococci.
OBJECTIVE
To investigate the ability of six fluorescent-based, two-colour viability assays to detect different physiological growth stages of two oral streptococci species.


RESULTS
The growth of Streptococcus sanguinis and Strep. mutans from 0 to 73 h culture periods was monitored by cell labelling with six mixtures of fluorescent stains, in addition to the growth parameters optical density (O.D.), log values of the total cell counts (log BC ml(-1)) and of the colony-forming units (log cfu ml(-1)).


CONCLUSIONS
In comparison with the corresponding cfu values as control, the vitality proportions determined by the Syto 9/PI test best reflected the dynamic growth pattern of both test strains. The direct fluorescent-based, two-colour assay Syto 9/PI provides valuable information about microbial viability stages.


CONCLUSIONS
The detection of viable but non-culturable bacteria requires more precise direct methods such as the fluorescent staining technique presented here, in addition to the classical plate count method.
Decker
E M
EM
Department of Conservative Dentistry, School of Dental Medicine, University of Tübingen, Osianderstrasse 2-8, D-72076 Tübingen, Germany.
D015169:Colony Count, Microbial / Q000379:methods*; D005452:Fluoresceins; D005456:Fluorescent Dyes; D013194:Staining and Labeling; D013295:Streptococcus mutans / Q000254:growth & development*; D013298:Streptococcus sanguis / Q000254:growth & development*
D005452:Fluoresceins; D005456:Fluorescent Dyes; C024098:6-carboxyfluorescein; C018506:diacetylfluorescein