Post-pH effect in oral streptococci.
OBJECTIVE
To study the post-pH effect (PpHE) in 11 strains of oral streptococci belonging to Streptococcus sanguis, S. mitis, S. gordonii, S. mutans and S. sobrinus by using the BacT/Alert microbial detection system.


METHODS
The bacterial cultures were exposed to a different pH (3.6, 4.0, 4.6, 5.0, 5.6, 7.0, 7.5, 8.0 and 8.6) for 1 h, and then returned to a neutral medium. The automated BacT/Alert system determined resumed microbial growth by measuring CO2 generation. The PpHE expresses the time difference between resumed growth (after pH shock) and optimal growth (pH 7.0 used as the control).


RESULTS
PpHE was found to be minimal for alkaline pH values, and to be strain and species dependent.


CONCLUSIONS
The PpHE may be useful as an ecological determinant or as an indicator of the cariogenicity of oral streptococci.
Castillo
A
A
Department of Microbiology, Medicine and Odontology, University of Granada, Granada, Spain. anamc@goliat.ugr.es
Rubiano
S
S
Gutiérrez
J
J
Hermoso
A
A
Liébana
J
J
D002245:Carbon Dioxide / Q000032:analysis; D003114:Colony-Forming Units Assay; D003773:Dental Plaque / Q000382:microbiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D013291:Streptococcus / Q000254:growth & development / Q000302:isolation & purification / Q000472:pathogenicity*
D002245:Carbon Dioxide