The following paper documents DNA signs of Acanthameoba in 49% of contact lenses from health patients. Most of those were not viable organisms but the fact that they are present should give use all pause in our recommendations for care. I have found that most patients are misinformed in proper CL care. Specifically they are under the impression that cleaning of the contact lens case is either unnecessary or can be done by rinsing in tap water. Over time, a biofilm will deposit in the case which will resist efforts at disinfection with typical solutions. The case should be cleaned only with sterile contact lens solution and should be changed once per month or or placed in boiling water to disinfect the case.
The majority of CL cases will grow multiple bacteria and fungi. It is remarkable that more infections do not occur. The normal tear film and epithelium are resistant to infection. Breaks in these from micro trauma predispose to infection which my be from atypical organisms related to the reservoir in the case.