4.3.4 The Nordmann/Dortet/Poirel test
The Nordmann/Dortet/Poirel (NDP) test can detect the presence of ESBL-producing bacteria in blood samples in less than two hours (Nordmann et al., 2012). As you might remember from Week 4, ESBLs are a major determinant of resistance to cephalosporin antibiotics. The presence of ESBLs in a bacterial strain can be used to diagnose a cephalosporin-resistant infection. The NDP test detects the enzyme activity of ESBLs in the sample.
What enzymatic reaction do ESBLs catalyse?
Answer
Recall from Week 3 that β-lactamases destroy β-lactam antibiotics by hydrolysing the β-lactam ring.
When cefotaxime (a third-generation cephalosporin) is hydrolysed by ESBLs, it results in acidification ; that is, the sample becomes more acidic. In the NDP test, this acidification can be measured as a colour change in the sample using a pH indicator . The colour of a sample gives a visible indication of the presence of ESBL-producing bacteria (Figure 13).
OpenLearn - Understanding antibiotic resistance
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