Identification of Naegleria fowleri in Domestic Water Sources by Nested PCR

Abstract

The free-living amoeboflagellate Naegleria fowleri is the causative agent of primary amoebic meningoencephalitis (PAM), a rapidly fatal disease of the central nervous system. In the United States, the disease is generally acquired while swimming and diving in freshwater lakes and ponds. In addition to swimming, exposure to N. fowleri and the associated disease can occur by total submersion in bathwater or small backyard wading pools. In the present study, swipe samples and residual pipe water from homes in Arizona were examined for N. fowleri by nested PCR due to the death of two previously healthy children from PAM. Since neither child had a history of swimming in a freshwater lake or pond prior to the onset of disease symptoms, the domestic water supply was the suspected source of infection. Of 19 samples collected from bathroom and kitchen pipes and sink traps, 17 samples were positive for N. fowleri by PCR. A sample from a Micro-Wynd II filter was obtained by passing water from bathtubs through the filter. Organisms attached to the filter also tested positive by PCR. The two samples that tested negative for N. fowleri were one that was obtained from a kitchen sink trap and a swipe sample from the garbage disposal of one home.

Rapid, Sensitive, and Discriminating Identification ofNaegleriaspp. by Real-Time PCR and Melting-Curve Analysis

“…Recently, there has been a move toward direct detection of N. fowleri by extraction of DNA from environmental samples and amplification by N. fowleri-specific PCR (15,26). Such a method is attractive because it has the potential to be more rapid, since it eliminates the cultivation step, and because it removes the need for microscopists experienced in the generic identification of Naegleria species.…”

“…A second consequence is that N. fowleri can colonize and proliferate in artificial aquatic environments such as swimming pools, cooling systems, and water supplies when temperatures are suitable, 25°C and above, becoming progressively more selective up to approximately 42°C (7,9). Analysis of environmental samples may have an epidemiological purpose, identifying sources of recent N. fowleri infection (15), or be prospective, as an element of risk assessment (3). In either case, the timeliness of identifications can be critical.…”

Causes of Outbreaks Associated with Drinking Water in the United States from 1971 to 2006

“…Numbers are dependent on reporting and surveillance activities in individual states and do not necessarily indicate that more outbreaks occurred in a given state. (4,25) after exposure to drinking water; the exposure route was thought to be inhalation rather than ingestion. One death was attributed to norovirus.…”

“…C. parvum (n ϭ 9) or Cryptosporidium not identified to the species level (n ϭ 1) was identified in 10 sole-pathogen outbreaks (10.1%). Single outbreaks of E. histolytica (37), Cyclospora (17), and N. fowleri (4,25) were also reported. Two outbreaks (2.0%) involving multiple parasites were identified; both involved G. intestinalis, one with E. histolytica and one with C. parvum.…”

Biology and pathogenesis of Naegleria fowleri

“…An indirect immunofluorescence assay (IIF) for the recognition of N. fowleri antigen in paraffin-embedded brain tissue slide is routinely performed at Centers for Disease Control. Additionally, PCR-based assays have been established for the sensitive, rapid, and precise identification of N. fowleri in clinical samples, and cultured amoebae from patients and the environment (14,(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) (Table 1).…”