Assessment of Water Quality by Fluorescent Antibody Identification
69
Table 2 shows the percentage of the positive precipitin reactions obtained with 80
fecal streptococcal strains freshly isolated from water and sewage. While 65% of S.
liquefaciens gave positive precipitin reactions, only 30% of S. faecalis and 35% of S.
faecium yielded positive precipitin tests. Moreover, none of the 20 S. durans strains was
positive. Only 32.5% of the group D streptococcus were determined as precipitin positive.
Our previous studies demonstrated that the FA techniques are applicable for the rapid
identification of the fecal streptococci (Pavlova et al, 1971). Employing the direct
staining method and individual and pooled conjugates a high percent of specific
fluorescence was achieved. The specificity of the conjugates and fluorescent staining was
assessed by absorption and inhibition tests utilizing controls with homologous and
heterologous antigens. Trypsinization of the smears prior to staining eliminated all FA
cross-reactions observed with non-fecal streptococci and staphylococci.
Table 3 illustrates the percent positive FA reactions by fecal streptococci with pooled
D conjugate employing the direct staining method. On the basis of 10 strains of each
species it was possible to obtain 81% positive FA reactions with this conjugate. Among
the individual species, however, S. faecium, S. durans and S. bovis which have been
reported as difficult to designate serologically, gave encouragingly high rates of positive
FA reactions.
In Figs. 1 - 6 is shown the fluorescence achieved by the species of fecal streptococci.
Fig. 1 shows the typical morphology of S. faecalis, giving brilliant yellow-green
fluorescence with the cells sharply outlined. This was rated 4+. Figs. 2 - 6 show similar
results with the other species.
It was also found that the percent positive reactions were lower with the precipitin test
(75%) than with the direct FA method (87%).
It was also observed that freshly isolated streptococcal D strains gave a higher
percentage of positive precipitin and FA reactions than did stock cultures obtained from
various culture collections. This suggested the possibility of employing FA procedures,
using our group D conjugates, for the rapid and economical identification of fecal
streptococci as indicators of water pollution. Furthermore, our observations that freshly
isolated strains showed greater positive response to the precipitin and FA reactions
rekindled our belief that these organisms could be employed as indicators of recent
pollution. Likewise, the fact that various species are predominant in the enteric system of
man, while others are predominant in animals, further exemplifies the usefulness of these
organisms in tracing the source of the fecal pollution.
A comparison of biochemical, precipitin and FA reactions of the 80 fecal
streptococcal strains that were freshly isolated from water and sewage is shown in Table
2. When the serological data were compared it was found that 66.3% of the total number
of the strains yielded positive FA reactions while only 32.5% were precipitin positive.
Moreover, it was determined that smears prepared from various fecal streptococcal
strains grown simultaneously in glucose-Lemco broth and on PSE agar and stained by the
direct method yielded the same degree of fluorescence. Following this observation all
smears for FA determination were prepared directly from the colonies on PSE agar. Using
this procedure fecal streptococci can be indicated from water samples within 20 hours,
whereas employing the glucose-Lemco broth and the necessary washings it requires
approximately 42 hours. Parenthetically it should also be noted that employing the
routine biochemical and precipitin tests the identification procedures may take as long as
7 to 14 days.
The ease with which the FA method can be employed for the rapid enumeration and
69
Table 2 shows the percentage of the positive precipitin reactions obtained with 80
fecal streptococcal strains freshly isolated from water and sewage. While 65% of S.
liquefaciens gave positive precipitin reactions, only 30% of S. faecalis and 35% of S.
faecium yielded positive precipitin tests. Moreover, none of the 20 S. durans strains was
positive. Only 32.5% of the group D streptococcus were determined as precipitin positive.
Our previous studies demonstrated that the FA techniques are applicable for the rapid
identification of the fecal streptococci (Pavlova et al, 1971). Employing the direct
staining method and individual and pooled conjugates a high percent of specific
fluorescence was achieved. The specificity of the conjugates and fluorescent staining was
assessed by absorption and inhibition tests utilizing controls with homologous and
heterologous antigens. Trypsinization of the smears prior to staining eliminated all FA
cross-reactions observed with non-fecal streptococci and staphylococci.
Table 3 illustrates the percent positive FA reactions by fecal streptococci with pooled
D conjugate employing the direct staining method. On the basis of 10 strains of each
species it was possible to obtain 81% positive FA reactions with this conjugate. Among
the individual species, however, S. faecium, S. durans and S. bovis which have been
reported as difficult to designate serologically, gave encouragingly high rates of positive
FA reactions.
In Figs. 1 - 6 is shown the fluorescence achieved by the species of fecal streptococci.
Fig. 1 shows the typical morphology of S. faecalis, giving brilliant yellow-green
fluorescence with the cells sharply outlined. This was rated 4+. Figs. 2 - 6 show similar
results with the other species.
It was also found that the percent positive reactions were lower with the precipitin test
(75%) than with the direct FA method (87%).
It was also observed that freshly isolated streptococcal D strains gave a higher
percentage of positive precipitin and FA reactions than did stock cultures obtained from
various culture collections. This suggested the possibility of employing FA procedures,
using our group D conjugates, for the rapid and economical identification of fecal
streptococci as indicators of water pollution. Furthermore, our observations that freshly
isolated strains showed greater positive response to the precipitin and FA reactions
rekindled our belief that these organisms could be employed as indicators of recent
pollution. Likewise, the fact that various species are predominant in the enteric system of
man, while others are predominant in animals, further exemplifies the usefulness of these
organisms in tracing the source of the fecal pollution.
A comparison of biochemical, precipitin and FA reactions of the 80 fecal
streptococcal strains that were freshly isolated from water and sewage is shown in Table
2. When the serological data were compared it was found that 66.3% of the total number
of the strains yielded positive FA reactions while only 32.5% were precipitin positive.
Moreover, it was determined that smears prepared from various fecal streptococcal
strains grown simultaneously in glucose-Lemco broth and on PSE agar and stained by the
direct method yielded the same degree of fluorescence. Following this observation all
smears for FA determination were prepared directly from the colonies on PSE agar. Using
this procedure fecal streptococci can be indicated from water samples within 20 hours,
whereas employing the glucose-Lemco broth and the necessary washings it requires
approximately 42 hours. Parenthetically it should also be noted that employing the
routine biochemical and precipitin tests the identification procedures may take as long as
7 to 14 days.
The ease with which the FA method can be employed for the rapid enumeration and