|Year : 2015 | Volume
| Issue : 3 | Page : 349-350
Free living amoebae: Acanthamoeba species pose a great risk for human health
Department of Medical Microbiology, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey
|Date of Submission||18-Jan-2015|
|Date of Acceptance||18-Feb-2015|
|Date of Web Publication||12-Jun-2015|
Department of Medical Microbiology, Cerrahpasa Medical Faculty, Istanbul University, Istanbul
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Kocazeybek B. Free living amoebae: Acanthamoeba species pose a great risk for human health. Indian J Med Microbiol 2015;33:349-50
|How to cite this URL:|
Kocazeybek B. Free living amoebae: Acanthamoeba species pose a great risk for human health. Indian J Med Microbiol [serial online] 2015 [cited 2020 Jan 28];33:349-50. Available from: http://www.ijmm.org/text.asp?2015/33/3/349/158544
The article by Khurana et al.  reports the presence of free living amoeba in the hospital water sources. Several amoebae species are pathogenic and host other pathogens but their infection risk are not well known.  Among them, only four genera including Acanthamoeba, Naegleria, Balamuthia, and Sappinia cause opportunistic and nonopportunistic infections in humans and animals. Acanthamoeba spp. and Balamuthia mandrillaris cause granulomatous amoebic encephalitis (GAE) while Naegleria fowleri causes primary amoebic meningoencephalitis (PAM).
Free living amoebae (FLA) may act as a Trojan horse and resembles vertebrate macrophages and can serve as hosts for a large number of pathogenic bacteria and viruses for humans including Coxsackievirus, Adenovirus and Echovirus and for amoeba-resistant bacteria (ARB) like Legionella spp., Chlamydophila pneumoniae, Mycobacterium avium, Listeria monocytogenes, Pseudomonas aeruginosa and Francisella tularensis as well as emerging pathogens, such as Bosea spp., Simkania negevensis, Parachlamydia acanthamoebae, and Legionella-like amoebal pathogens.  The genus Acanthamoeba has been placed in the family Acanthamoebidae. Acanthamoeba species are among the most important FLA and known to cause central nervous system (CNS) infection in immunocompromised and rarely disseminated infections in skin and lungs, and keratitis in immunocompetent hosts. Thus, since an increase in the number of cases of Acanthamoeba infections has occurred worldwide, recently, these organisms have gained attention due to their role in causing serious and sometimes fatal human infections. Acanthamoeba has been isolated from sea water, soil, surgical instruments, contact lenses, dialysis units, human nasal cavities, throat, cerebrospinal fluids. The presence of FLA in tap water may represent a health risk to both immunocompromised and immunocompetent individuals.  Acanthamoeba is ubiquitously present in the environment and Acanthamoeba antibodies are present in up to 100% healthy populations in New Zealand and Pakistan. , Considering the mode of transmission to humans, easily by inhalation or inoculation through skin lesions may explain this high Acanthamoeba antibody prevalance.
There are some reports from the countries like Iran, Egypt, Brasil. Lasjerdi et al.,  investigated the occurrence of FLA in immunodeficiency wards of hospitals in Iran and detected 38 (52.9%) samples positive for FLA. Acanthamoeba belonging to the T4 genotype was the most prevalent isolate in their study and they concluded that the presence of the T4 genotype on medical instruments, should be of concern to the health authorities. Hassan et al.,  investigated Acanthamoeba species in haemodialysis and dental units in Egypt and they found that 42.9% of water samples from the hydraulic systems of both haemodialysis and dental units were positive for Acanthamoeba.
Some bacteria escape the killing mechanisms of Acanthamoeba and cleverly use the amoeba as a trojan horse for their own benefit and protect themselves by secreting soluble anti-Acanthamoeba substances or directly injecting such substances into Acanthamoeba through the type III secretory system. Acanthamoeba and bacteria frequently encounter each other in the environment routinely. 
As discussed above, Acanthamoeba species which were isolated from tap water or intensive care units (ICUs) or immunodeficiency wards of hospitals, must take into account both ways. One of them is pathogenic properties of amoebae, for example encephalitis, keratitis and dermatologic manifestations, and the other threat is to act like a trojan horse for pathogenic bacteria.
It is clinically difficult to diagnose the amoebic diseases and there may be delays to diagnose and to treat patients. Therefore, an investigation of the connection between environment and the patient's infections is essential. Knowledge of prior prevalence of amoebae in the region may help physicians to diagnose and treat either healthy or immunocompromised individuals. Acanthamoeba spp. can resist water treatment for sanitizing drinking water as well.  Coskun et al.,  detected Acanthamoeba spp, 9 out of 33 detected in tap water samples. Kaushal et al.,  reported Acanthamoeba encephalitis in a 63-year-old female from India where acanthamoebae were demonstrated and cultured from cerebrospinal fluid (CSF). In spite of treatment with amphotericin B, fluconazole and rifampicin the patient did not survive, because there is no effective treatment for this disease. Recent studies show the importance of suspecting and evaluating patients for amoebic causes of CNS infections in order to prevent misdiagnosis and inappropriate treatment. More than 400 cases caused by FLA have been reported in world literature with only two to three percent survival.
As a result, we suggested Acanthamoeba species as important pathogen for human health for the following characteristics of this FLA. The resistance of Acanthamoeba spp. to water treatment for sanitizing drinking water and the presence of Acanthamoeba antibodies in up to 100% healthy populations together with escaping of some bacteria from the killing mechanisms of Acanthamoeba and also treatment difficulties make them non-negligible potantial threat to the human health.
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