I have a question regarding Legionella infections… How does Legionella DNA end up in blood and urin? During pneumonia, one can detect Legionella DNA in blood and urine samples, but I can not really explain to myself, how it gets there. It probably has something to do with the immune system, degradation of bacterial cells within macrophages, kidney blood filtering... It is probably the same with other pneumonia-causing bacteria, as PCR is also used to detect their DNA in this samples. I am searching for an article about it, but I can not seem to find it.