Environmental Engineering Reference
In-Depth Information
Escherichia coli
is one of the most commonly studied bacterial strains not only for its
pathogenic capability but also because it is the main cause of diarrhea in poor countries,
leading to the death of a million children every year [21]. The prevalence of these bacteria
is lower in teenagers and adults; however, the intake of food with a high content of this
microorganism (10
8
-10
10
CFU) can produce gastroenteritis with liquid diarrhea in these
age groups. Table 30.9 shows the bactericidal effect of ZZ on three strains of
E. coli
.
Among microorganisms,
V. cholerae
is of the greatest importance because of the damage
it causes when ingested in contaminated drinking water and food.
Vibrio cholerae
is the
causal agent of a cholera epidemic [22]. This acute diarrheal illness leads to a rapid loss of
body luids and electrolyte balance, and eventually to death in 24 h as a consequence of its
powerful enterotoxins. Thus, the effect of ZZ on serotypes Inaba and Ogawa was evalu-
ated. As observed in Table 30.10, the two serotypes were eliminated after 30 min of expo-
sure to ZZ in stirred conditions, although in static serotype Inaba required 2 h of exposure.
Shigella sonnei
was studied using two different doses (10
5
and 10
2
CFU) considering that
the infective dosage of these bacteria is low; that is, few cells can make a person ill depend-
ing of the strain virulence, but it generally takes from 10 to 100 cells [23]. The time of inac-
tivation of both inocula was the same between 2 and 3 h for both conditions of the test
culture, stirred and static (Table 30.11). The same result was obtained for
Salmonella typhi
using the infective dose of 10
8
CFU; in both conditions, the total inhibition of the bacteria
was completed by 3 h.
Pseudomonas aeruginosa
is considered an opportunist bacterium quite abundant in
nature. These bacteria can infect patients with immunological deiciency, cancer, or burns,
TABLE 30.9
Bactericidal Effect of ZZ on
Escherichia coli
O:149 K88 Lt(+),
Escherichia coli
O:101
K99 St(+), and
Escherichia coli
ATTC 25922
CFU
Time
ZZ Stirred
Control
ZZ Static
Control
0
3 × 10
9
3 × 10
9
3 × 10
9
3 × 10
9
15 min
1.6 × 10
3
1 × 10
8
6 × 10
6
1 × 10
8
30 min
-
3 × 10
7
-
2.3 × 10
7
1 h
-
6 × 10
7
-
6.5 × 10
7
2 h
-
2.2 × 10
7
-
3 × 10
7
3 h
-
5.2 × 10
7
-
6.2 × 10
7
TABLE 30.10
Bactericidal Effect of ZZ on
Vibrio cholerae
Serotypes
Ogawa and Inaba
Vibrio cholerae
C7258 (CFU)
Vibrio cholerae
C6706 (CFU)
ZZ
Stirred
ZZ
Stirred
Time
Control
ZZ Static
Control
Control
ZZ Static
Control
0
7 × 10
9
7 × 10
9
7 × 10
9
7 × 10
9
7 × 10
9
7 × 10
9
7 × 10
9
7 × 10
9
15 min
1 × 10
4
8 × 10
9
1 × 10
5
7.5 × 10
9
6.5 × 10
9
6 × 10
9
3 × 10
9
6 × 10
9
30 min
-
7.5 × 10
9
-
7 × 10
9
1 × 10
1
5.8 × 10
9
2.8 × 10
9
6 × 10
9
1 h
-
8 × 10
9
-
5 × 10
9
-
6 × 10
9
1 × 10
2
5.8 × 10
9
2 h
-
8 × 10
9
-
6 × 10
9
-
6.5 × 10
9
-
5 × 10
9
3 h
-
6 × 10
9
-
4 × 10
9
-
6 × 10
9
-
4.8 × 10
9
