Comparison of culture-based methods to enumerate Escherichia coli in tropical and temperate freshwaters.
OBJECTIVE
The specificity of a method for the enumeration of Escherichia coli (chromocult agar, CC) was tested using freshwater samples from a tropical area (Cuba Island) by isolating colonies and identifying them with API (Appareillage et procédé d'identification) strips. Enumerations of E. coli by the most probable number (MPN) microplate method were compared with counts on chromogenic and fluorogenic agar media [CC, rapid E. coli (REC), fluorocult] in tropical and temperate freshwater samples.


RESULTS
A high percentage of specificity (95.7%) for the CC agar enumeration of E. coli was observed. High regression coefficients (log-log linear regressions) were found between E. coli counts on agar media and by the MPN method. In the tropical environment, counts with REC medium were significantly different from those obtained with the other methods. MPN counts were found to be significantly higher than those obtained using the plate counts methods in the temperate environment.


CONCLUSIONS
Escherichia coli enumeration methods based on glucuronidase activity appear to be suitable for the evaluation of microbiological quality in the tropical environment featured in this study.


CONCLUSIONS
The methods for the enumeration of E. coli tested in this study should help improve the evaluation of microbiological contamination of Cuban freshwaters.
Prats
J
J
Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Bruxelles, Belgium.
Garcia-Armisen
T
T
Larrea
J
J
Servais
P
P
D015169:Colony Count, Microbial / Q000379:methods; D004926:Escherichia coli / Q000201:enzymology / Q000254:growth & development*; D029968:Escherichia coli Proteins / Q000378:metabolism; D005618:Fresh Water / Q000382:microbiology*; D005966:Glucuronidase / Q000378:metabolism; D016014:Linear Models; D015203:Reproducibility of Results
D029968:Escherichia coli Proteins; D005966:Glucuronidase