“Floaters” versus “Nesters”
The E Coli bacteria that cause your UTI start out as “floaters” swimming around in your bladder; the medical community calls these “planktonic” bacteria. These are the bacteria that antibiotics can identify and kill. But that’s all they do. They are not able to detect or deal with some of the bacteria which sneak into your bladder, or other parts of the urinary tract, and begin to “nest” there.
As part of the “nesting” process, these bacteria surround themselves with a slimy protective sac (the biofilm) in order to evade the impact of the antibiotics. And once you have stopped taking the antibiotics, they will begin to emerge again causing a relapse, which starts the same bacterial infection all over again. What’s worse, you may have several of these biofilms in your urinary tract.
In short, the individual “floater” bacteria are susceptible to antibiotics, but once they clump together, the bacteria morph into complex 3D structures which are not able to be penetrated by antibiotics or chemicals.
Below is an illustration of the three stages of biofilm formation: the attachment to the bladder lining; growth within the protected environment of the biofilm coating; and the repeated dispersal of bacteria into the bladder to create active infections.
Source: Center for Biofilm Engineering, Montana State University