U.S. Food and Drug Administration regulations governing bottled water
include microbiological quality guidelines based on coliform counts. R
ecently, a new MF medium for simultaneous detection of total coliforms
and Escherichia coli was developed. This medium, m-ColiBlue24 (m-CB)
was compared to m-Endo medium and an International Organization for St
andardization standard coliform medium, lactose agar with Tergitol 7.
Coliform analysis was conducted on 104 brands of bottled water from 10
countries. Some samples were additionally analyzed for heterotrophic
plate count and Pseudomonas sp, populations, including P. aeruginosa.
Presumptive coliform colonies were found in 5.8% of the samples with m
-CB, 1.9% with m-Endo and 11.5% with lactose agar with Tergitol 7. Non
e of the presumptive coliforms from any of the three media were verifi
ed as true coliforms in subsequent analysis. Consequently, the presump
tive recovery rates actually represented false-positive error (FPE) ra
tes. The FPE for m-CB and m-Endo were not statistically different (P <
0.05) but the FPE for lactose agar with Tergitol 7 was significantly
larger.