The Acanthamaoeba sp. is in the genus amoebae and these species can be commonly found in soil and fresh water. Most of these species are free living and feed on bacteria, and on rare ocassions have been known to cause infections in humans and other animals.
These species exist as cysts in the external environment and as trophozoites (feeding stage) in the host or internal environment. They are spread through direct transmission, meaning that they enter through an open lesion on the skin or inhaled into the respiratory tract, where they can infect internal lesions. They replicate through mitosis.
There are two infections that are known to be caused by the Acanthamoeba species; amoebic keratitis and Granulomatous amoebic encephalitis.
Amoebic keratitis is a result of a species of acanthamoeba infecting the eye creating corneal ulcers and possibly blindness. This infection is common among contact lens users that do not properly clean their lenses or wash their hands before handling their lenses.
Granulomatous amoebic encephalitis occurs in people with immunodeficiencies, diabetes, or are malnourished. The parasite enters through open lesions and spreads into the central nervous system, leading to neural damage and possible fatality within days. Symptoms of this infection are altered mental status, headaches, fever, neck stiffness, seizures, and focal neurological signs.
A recent study from the University of Bath demonstrates that MRSA (Methicillin resistant staphylococcus aureus) can replicate inside the cyst form of Acanthamoeba polyphaga. These cysts then act as an airborne tranmission vector for the MRSA.