|
| Table 1. Bacterial counts and percentages of antibiotic resistant coliforms on EMB agar in water samples collected from raw and treated sewage on four different sampling dates, at the Antofagasta sewage treatment plant. |
|
Date |
Samples |
Ampicillin |
Tetracycline |
Chloramphenicol |
Streptomycin |
Total |
||||
|
CFU/ml |
% |
CFU/ml |
% |
CFU/ml |
% |
CFU/ml |
% |
|||
|
September |
Raw |
2500 |
2,8 |
190 |
0.2 |
850 |
1.0 |
750 |
0.9 |
87000 |
|
Treated |
20 |
13,3 |
5 |
3.3 |
3 |
2.0 |
11 |
7.3 |
150 |
|
|
December |
Raw |
2900 |
1.7 |
1400 |
0.8 |
1800 |
1.1 |
1900 |
1.1 |
170000 |
|
Treated |
14 |
17.9 |
7 |
9.0 |
5 |
6.4 |
10 |
12.8 |
78 |
|
|
March |
Raw |
4900 |
1.8 |
7500 |
0.3 |
670 |
0.2 |
640 |
0.2 |
270000 |
|
Treated |
30 |
11.5 |
5 |
1.9 |
3 |
1.2 |
9 |
3.5 |
260 |
|
|
July |
Raw |
2400 |
1.3 |
180 |
0.1 |
530 |
0.3 |
420 |
0.2 |
180000 |
|
Treated |
20 |
7.4 |
3 |
1.3 |
4 |
1.7 |
7 |
3.0 |
230 |
|
| The differences of the proportions of resistant bacterial counts between raw and treated sewage is significant P < 0,05. |
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