Fig. 1.
![Variability summary for RD [%].](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/64727c1c215d2f6c89dc9f62/j_pjm-2023-039_fig_002.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=AKIA6AP2G7AKOUXAVR44%2F20251206%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20251206T002511Z&X-Amz-Expires=3600&X-Amz-Signature=910aad14035ceb910d060757bf0e913dc5cb71753d4eda0c478424122dc64dad&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Confirmatory tests for Clostridium perfringens according to Directive 98/83/EC_
| Feature | Clostridium perfringens |
|---|---|
| Sucrose fermentation | sucrose-positive – yellow and matte colonies |
| Possess acid phosphatase | change of color of the colony from yellow to pink in ammonium hydroxide vapors |
Confirmatory tests for Clostridium perfringens according to ISO/CD 6461-2:2002_
| Feature | Clostridium perfringens |
|---|---|
| Reduction of sulphites to sulphides | black or grey colonies |
| Motility | none |
| Reduction of nitrate to nitrites | orange/red-colored medium after the addition of the Nessler reagent |
| Lactose fermentation | orange or yellow-colored medium with lactose (acidification of the medium and gas formation) |
| Protease formation | gelatine liquefaction |
Comparison of the results of confirmation tests for Clostridium perfringens_
| Characteristics of Clostridium perfringens presumptive confirmed colonies | TSC ISO/CD 6461-2:2002 | mCP Directive 98/83/EC |
|---|---|---|
| Number of all confirmed colonies | 466 | 381 |
| Typical colonies, confirmed positive (true positive) | 150 | 107 |
| Atypical colonies, confirmed positive (false negative) | 33 | 11 |
| Typical colonies, confirmed negative (false positive) | 196 | 79 |
| Atypical colonies, confirmed negative (true negative) | 87 | 184 |
| Typical colonies, non-detection error | 0.18 | 0.09 |
Comparison of performance parameters of procedures used for detection of Clostridiun perfringens in water samples_
| Performance parameters | TSC ISO/CD 6461-2:2002 | mCP Directive 98/83/EC |
|---|---|---|
| Sensitivity | 82.0% | 90.7% |
| Specificity | 30.7% | 70.0% |
| Selectivity | 32.2% | 28.1% |
| False negative rate | 27.5% | 5.6% |
| False positive rate | 56.6% | 42.5% |
| Efficiency | 50.9% | 76.4% |