When someone develops an infection that involves antibiotic-resistant bacteria, antibiotics will not help. That makes these types of infections harder to treat.  

One example is ESBL-producing bacteria; these highly resistant micro-organisms (HRMOs) produce an enzyme called extended spectrum beta-lactamase, which breaks down some commonly used antibiotics, making these drugs ineffective for treating the infection. Sewage is subjected to extensive testing to check for these and other dangerous and rare HRMOs. This allows RIVM to monitor where these bacteria occur in the Netherlands and to what extent. This information is important in order to reach decisions regarding appropriate measures.