If you have experienced bacteria problems in the past, it is recommended that you test your well more frequently. “Indicator” organisms Water pollution caused by fecal contamination is a serious problem due to the potential for contracting diseases from pathogens (disease-causing organisms).Frequently, concentrations of pathogens from fecal contamination are small, and the number of different possible pathogens is large.f you have experienced bacteria problems in the past, it is recommended that you test your well more frequently. “Indicator” organisms Water pollution caused by fecal contamination is a serious problem due to the potential for contracting diseases from pathogens (disease-causing organisms).