Acanthamoeba

Danger in the Water

canthamoeba is one Most people will be exposed Aof the most to Acanthamoeba during their common types of protozoa in lifetime and will not get sick. soil and is often found in fresh In fact, 50 to 100% of the water. Most species supply population will have their metabolic needs by antibodies to Acanthamoeba eating bacteria, fungi and in their blood, and the by Jay Hardy, CLS, SM (NRCM) other protozoa. organism can be isolated from

the pharynx of many healthy individuals. Jay Hardy is the founder and president of Hardy Diagnostics. However, Acanthamoeba is He began his career in capable of causing several microbiology as a Medical Technologist in Santa Barbara, devastating infections in California. humans; and has only been

known to cause disease since In 1980, he began Figure 1: The Acanthamoeba

manufacturing culture media for trophozoite is seen here at 1,000X the 1970s. the local hospitals. Today, phase contrast. The organelles and Hardy Diagnostics is the third acanthapodia can be seen. It has largest media manufacturer in Amebic Keratitis no flagellar form, which is the U.S. One of the diseases caused by characteristic of Naegleria. Acanthamoeba is called To ensure rapid and reliable turn around time, Hardy amebic keratitis, which is an Acanthamoeba is a Diagnostics maintains six infection of the eye.

distribution centers, and microscopic, free-living produces over 3,000 products ameba. This ameba has been used in clinical and industrial isolated from water (including microbiology laboratories throughout the world. natural and treated water in pools or hot tubs), soil, air (in www.HardyDiagnostics.com association with cooling

towers, heating, ventilation and air conditioner systems), sewage systems, and drinking Figure 2: Invasion of the cornea is water systems (shower heads, seen with amebic keratitis.

taps). Over 1,300 cases have been The prevalence of this described in the literature. The infection has risen in the past organism can live between the twenty years worldwide, contact lens and the cornea mainly because more people and will eventually invade the are wearing contact lenses. cornea producing a milky white ulcer. When people rinse their contact lens cases in tap Approximately 85% of all water, they become Figure 4: Tracks are seen as the amebic keratitis cases occur in contaminated with the amebae amebae feed upon the film of E. coli on a petri plate. The amebae people who wear contact that feed on bacteria. They are are seen at the end of each track lenses. The infection is very then transferred onto the (100X). painful and can lead to lenses and can live between blindness. the contact lens and the eye. This is particularly worrisome Disinfection Since the ameba can be found because most commercial in chlorinated swimming contact lens solutions do not Although the amebae can be pools and domestic tap water; kill the amebae. sensitive to the antiseptic people who wear lenses while chlorhexidine, the swimming or use tap water to In May of 2007, a contact lens concentration found in some rinse their lenses have an solution manufacturer recalled contact lens solutions is increased risk of infection. their product after the Centers usually not high enough to be The cysts are resistant to the for Disease Control found that effective. Another possible chlorine used to treat drinking 21 individuals had possibly disinfectant is water and swimming pools. received an Acanthamoeba polyhexamethylene biguanide infection after using the lens (PHMB) but is not always solution in the month prior to effective. This has also been diagnosis. suggested as a treatment. Hydrogen peroxide is another commonly used disinfectant; Diagnosis and Culturing however heat (at least 70oC) has been found to be the most Since Acanthamoeba feed effective means of killing the readily on E. coli bacteria, it organism. Figure 3: Both the cyst and can be cultured by inoculating trophozoite stages of a plate of Non-Nutrient Agar Acanthamoeba castellanii can be Treatment seen here at 400X. (G225) that has been previously inoculated with a The infection can be difficult The incubation period is a few film of E. coli. If to treat because the cyst is days. Keratitis typically Acanthameoba is present, tough and resilient. Current begins with a foreign-body “feeding tracks” will be seen treatment regimens usually sensation followed by pain, at 100X when the plates are include a topical (in this case, tearing, photophobia, placed under the microscope applied to the eye) cationic blepharospasm (twitching of and examined for up to ten (made with positive ions) the eyelid), and blurred days. antiseptic drug such as vision. polyhexamethylene biguanide (PHMB, 0.02%), or MRSA and Acanthamoeba chlorhexidine (0.02%) with or without a diamidine such as Oddly enough, due to the propamidine (0.1%), or amebae’s appetite for hexamidine (0.1%). Therapy bacteria, Methicillin Resistant may last six months to a year, Staphylococcus aureus and is best done with a (MRSA) organisms have been combination of drugs. found to be living inside the

Figure 5: An Acanthamoeba Acanthamoeba organism. Risk Factors abscess is seen here in brain tissue. Some strains have been found to contain MRSA in their The high risk factors are: Although the organism is cysts and have been an ubiquitous, there have only effective means of airborne • Improper storage and been 400 cases of dispersal of the drug resistant handling of lenses (the Acanthamoeba encephalitis bacteria. longer the life of the lens, reported worldwide. Most the greater the risk). cases occur in Summary immunocompromised • Improper disinfection of patients, and the survival rate Ancanthamoeba is a lenses; such as using tap is only two or three percent. potentially dangerous water or homemade Due to the infrequency of pathogen that can be solutions to clean the infection it is often controlled effectively if lenses. misdiagnosed and improperly precautions are taken. treated. The current • Not changing the lens case treatments such as Hardy Diagnostics offers a regularly. amphotericin-B, rifampicin, complete selection of products trimethroprim- for the culturing and • Swimming, using a hot sulfamethoxazole, maintenance of free-living tub, or showering while ketokonazole, fluconazole, amebae including wearing lenses. sulfadiazine, and albendazole Acanthamoeba and Naegleria. are of only limited value. • Coming into contact with • Non-Nutrient Agar, G225 contaminated water. • Pages Saline, R225 • Acanthamoeba Maintenance • Having a history of Broth, K225 trauma to the cornea. • Naegleria Maintenance Broth, K325

Granulomatous Amebic Encephalitis

Acanthamoeba can also be a Jay Hardy, CLS, SM (NRCM) cause of encephalitis by Figure 6: An Acanthamoeba cyst Santa Maria, CA entering cuts, wounds, or the in brain tissue (H&E stain). nostrils and spreading to the nervous system.