Naegleria Fowleri, a free-living amoeba (Free Living Amoeba or FLA), caused the death of a woman in the US. FLAs, of which many species are known besides the aforementioned, e.g., Acanthamoeba castellanii or Balamuthia mandrillaris and others, Hartmannella spp., Dictyostelium polycephalum live both in natural aquatic environments, ponds, lakes, and those constructed by the human species such as swimming pools or even spas. It has long been known that they can prove to be insidious and dangerous pathogens. The organs affected are essentially the eye, with a keratitis that can lead to blindness and an encephalitis, which in the case of Naegleria attacks the brain substance with particular virulence, with the nefarious outcomes referred to in the subject. https://doi.org/10.3390/proceedings2110692
FLAs, like all amoebas, feed on bacteria present in the aqueous environment in which they live, but it is known that interactions with bacteria are not only predatory and there are cases of symbiosis between FLAs and bacteria and viruses that regularly live in biofilms adhering to numerous substrates giving rise to interesting relationships. These biofilms can be found ubiquitously in nature, but also in water supply lines, plumbing systems in industry, plumbing systems in private homes, and even in health care areas. Within these biofilms are FLA and other microorganisms protected in such a way to some extent from conditions made difficult by, for example, countermeasures such as disinfection
A biofilm is in fact produced by aggregates of bacteria adhering to irregularities in the interior walls of water pipes and other wet structures, forming well-organized layers. http://old.iss.it/binary/publ/cont/13_16_web.pdf. Bacterial biofilms described for wet sites are many, and causing them are different species of bacteria, with different pathogenicity. Associations of this protozoan species with Vibrio cholerae, Mycobacterium ulcerans, Pseudomonas aeruginosa, Francisella phylomiragia are described. Well known is the Acanthamoeba-Legionella pneumoniae pattern.
The presence of Legionellae, the cause of epidemic-type outbreaks of pneumonia, carried by Acanthamoeba is described in air conditioning equipment and air conditioners, both for water and air cooling system (because of the volatility of the cysts, which are very light) and thus both in and out.
To date, its implication in nosocomial infections has not been well investigated, although there is some evidence regarding Legionella, which is closely associated with it, and the degree of containment exerted by current disinfection protocols has not been assessed, as for other protozoa.
In Italy , the incidence of amoebic granulomatous encephalitis by Acanthamoeba or invasive encephalitis by Naegleria is fortunately very low, almost anecdotal, but some autochthonous cases have been described in Italy even if sporadically and occasionally. It should be noted that FLAs behave as opportunists in immunodeficient and/or compromised patients and are vehicles for serious bacterial infections of nosocomial interest in hospital facilities, such as dialysis units.
Acanthamoeba keratitis (AC) is a rare, severe, and seriously debilitating corneal infection. Approximately 85% of CA cases occur in contact lens wearers, due to improper lens wear, although the condition can arise after corneal trauma, especially in rural settings. Although it has a low incidence (1 in 100,000 in Europe), CA is a potentially devastating eye infection for patients, as it can cause intense pain, vision deterioration, and, if not effectively treated, enucleation and blindness. Biguanide polyhexanide (PHMB) and chlorhexidine are in fact the only active ingredients effective in the cystic phase of the protozoan. https://www.oculistaitaliano.it/interviste/cheratite-da-acanthamoeba/.
It is worth noting that 85% of cases of keratitis caused by Acanthamoeba occur in contact lens wearers, and that it is significantly correlated with young age and male sex, probably related to less attention to personal hygiene, lack of proper care of contact lenses, and improper disinfection procedures.
Currently, amphotericin B is the only drug that has demonstrated some efficacy when administered intrathecally in primary amoebic meningoencephalitis.