In a hospital, what does a Legionella-negative test result indicate when samples are collected and analyzed properly?

A Legionella-negative test result indicates that Legionella bacteria were not detected in the samples collected and analyzed, which suggests that the water system is effectively managed concerning this pathogen. This result serves as an acceptable validation of the water management program, indicating that the strategies in place to mitigate the risk of Legionella growth—such as regular maintenance, monitoring water temperatures, and implementing disinfection protocols—are functioning adequately.

This negative result does not mean that waterborne infections are impossible, as there could be other pathogens present (thus not supporting the first choice). Similarly, it does not imply a failure of the water management program, as a Legionella-negative result suggests the program is working effectively. Lastly, there is no immediate need for water treatment since the current testing indicates that there is no Legionella present, which rules out the necessity for immediate action as suggested by the option regarding water treatment.