A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances (EPSs). The cells within the biofilm produce the EPS components, which are typically a polymeric conglomeration of extracellular polysaccharides, proteins, lipids and DNA. Because they have three-dimensional structure and represent a community lifestyle for microorganisms, they have been metaphorically described as “cities for microbes. They are highly resistant to antibiotics and are difficult to diagnose and treat accordingly as a result.

https://en.wikipedia.org/wiki/Biofilm

They attached to a foreign body like dermal filler and excrete a protective outer shell, over time they will learn how to train their cells to thrive and survive in challenging environments, thus making them bigger and more complex. Because of their complexity and their attraction of more than one organism, it may be that just one line of treatment in attempt of their destruction and resolution may not be sufficient.