76
N. Buras and Y. Kott
coli colonies developed at 44.5°C was smaller and the A. aerogenes and other coliforms
did not develop.
In comparing results summarized in Table 1 on a percentage basis (results obtained on
MmFC with incubation temperature 37°C being considered 100%), only 54.8% of E. coli
colonies developed when incubation temperature was 44.5°C. 93.5% of the E. coli
colonies developed on MmFC and incubation temperature 37°C were identified with
specific bacteriophages.
In the remaining 199 water samples tested - where E. coli bacteria were not present,
only A. aerogenes or other coliform bacteria developed. In these samples the numbers of
A. aerogenes varied from a few tenths as recorded in samples 13, 15, 16, 25, 31, 32, 38,
39 (Table 1) to several thousand - sample 37 - in 100 ml. The number of other coliforms
was generally low.
The results obtained on Μ-ΕηαΌ show that the total coliform count is sometimes
comparable to the one obtained on MmFC: mostly though the counts were higher or
lower, not consistent and no differentiation between the various coliforms could be
obtained.
DISCUSSION
Coliform bacteria reaching a water body may come from various sources. It is of great
importance in water quality control to establish their identity as well as their numbers.
The tests available do not answer these conditions. Most of them recommend growing the
coliform bacteria on various selective media (Perry et al, 1944; Vaughn, 1951). Some try
to single out the fecal coliforms by combining selective media and incubation at elevated
temperatures (Geldreich, 1965). The results obtained in these methods are not always
accurate. Subjected to the double stresses of medium and temperature, some of the fecal
coliforms fail to grow.
In water bodies with low degree of pollution, the recovery of every one of the
coliform bacteria present is of outmost importance. This is the reason why incubation at
or around optimal growth temperature is the most appropriate.
As the fecal coliforms are of great significance in establishing the source and degree of
pollution, it is important that their identification should be carried out with high
accuracy. The most accurate identification of bacteria known today is achieved by phage
typing. This is routine procedure in medical laboratories, but not in water bacteriology.
E. coli bacteria from urinary tract infections have been identified lately by Parisi (1969),
using specific bacteriophages. However, E. coli bacteria from water have never been
identified by specific bacteriophages.
The results obtained in the test described show that 93.5% of the E. coli present in the
water samples have been identified by the specific E. colibacteriophages available.
In water quality control when evaluating a method for its efficiency, a number of facts
have to be considered — among others that the results obtained should be reproducible
and the identity of the indicator bacteria should be established at once and accurately.
The results obtained so far show that these conditions are fulfilled. It is suggested
therefore that the test described in this paper be used, for the time being, in parallel with
the routine practice. It is hoped that in this way sufficient data will be accumulated to
confirm the accuracy of the test and its reliability.
N. Buras and Y. Kott
coli colonies developed at 44.5°C was smaller and the A. aerogenes and other coliforms
did not develop.
In comparing results summarized in Table 1 on a percentage basis (results obtained on
MmFC with incubation temperature 37°C being considered 100%), only 54.8% of E. coli
colonies developed when incubation temperature was 44.5°C. 93.5% of the E. coli
colonies developed on MmFC and incubation temperature 37°C were identified with
specific bacteriophages.
In the remaining 199 water samples tested - where E. coli bacteria were not present,
only A. aerogenes or other coliform bacteria developed. In these samples the numbers of
A. aerogenes varied from a few tenths as recorded in samples 13, 15, 16, 25, 31, 32, 38,
39 (Table 1) to several thousand - sample 37 - in 100 ml. The number of other coliforms
was generally low.
The results obtained on Μ-ΕηαΌ show that the total coliform count is sometimes
comparable to the one obtained on MmFC: mostly though the counts were higher or
lower, not consistent and no differentiation between the various coliforms could be
obtained.
DISCUSSION
Coliform bacteria reaching a water body may come from various sources. It is of great
importance in water quality control to establish their identity as well as their numbers.
The tests available do not answer these conditions. Most of them recommend growing the
coliform bacteria on various selective media (Perry et al, 1944; Vaughn, 1951). Some try
to single out the fecal coliforms by combining selective media and incubation at elevated
temperatures (Geldreich, 1965). The results obtained in these methods are not always
accurate. Subjected to the double stresses of medium and temperature, some of the fecal
coliforms fail to grow.
In water bodies with low degree of pollution, the recovery of every one of the
coliform bacteria present is of outmost importance. This is the reason why incubation at
or around optimal growth temperature is the most appropriate.
As the fecal coliforms are of great significance in establishing the source and degree of
pollution, it is important that their identification should be carried out with high
accuracy. The most accurate identification of bacteria known today is achieved by phage
typing. This is routine procedure in medical laboratories, but not in water bacteriology.
E. coli bacteria from urinary tract infections have been identified lately by Parisi (1969),
using specific bacteriophages. However, E. coli bacteria from water have never been
identified by specific bacteriophages.
The results obtained in the test described show that 93.5% of the E. coli present in the
water samples have been identified by the specific E. colibacteriophages available.
In water quality control when evaluating a method for its efficiency, a number of facts
have to be considered — among others that the results obtained should be reproducible
and the identity of the indicator bacteria should be established at once and accurately.
The results obtained so far show that these conditions are fulfilled. It is suggested
therefore that the test described in this paper be used, for the time being, in parallel with
the routine practice. It is hoped that in this way sufficient data will be accumulated to
confirm the accuracy of the test and its reliability.