The growth of “bio-films” or organic matter (usually referred to as white slime) in air handler drain pans and drain lines has been a known HVAC industry issue. The occurrence of the organic matter in the field is typically reported during warm season when air handler units are usually running in cooling mode. This growth typically leads to water overflow in the drain pan and unit shutting off due to triggering of the overflow switch.
For additional information on this issue and how to address it: Download the Field Communication (PDF)