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Quiz 73

Presentation of Quiz #73

A 49-year-old male was admitted to the hospital with a 4-day history of altered mental status, nausea, vomiting, malaise and high fever.  The patient was lethargic with neck stiffness.  Although specific viral, bacterial and fungal pathogens were negative, as was bacterial culture, she was suspected of having meningitis.  She expired 4 days later.  On autopsy, the following images were seen from brain tissue; the causative agent was confirmed by studies at CDC.


  • With many microbiology causative agents ruled out, what other causes should be considered?
  • What additional tests should be performed?  Why or why not?
  • Based on additional testing, what do you suspect as the causative agent?

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 Answer and Discussion of Quiz #73
The images from the autopsy and examination of brain tissue, revealed the presence of Naegleria fowleri trophozoites.  This presumptive diagnosis was consistent with the fact no cysts were seen in the tissue sections.  Additional studies using specific FA reagents also revealed the following image of Naegleria fowleri.


Additional patient information
Additional patient history from friends and relatives revealed no recreational fresh water exposure during the previous two weeks.  However, she regularly used a neti pot to cleanse her sinuses.  Based on further discussions, it was assumed that she did not use distilled, filtered, or previously boiled water for nasal irrigation.

Nasal cleansing using neti pots can provide relief to patients with sinusitis who have symptoms of facial pain, headache, cough, rhinorrhea (allergic rhinitis) and nasal congestion. Nasal irrigation is performed using a device shaped like Aladdin’s lamp that is filled with saline. The water flows out the tip of the pot into one nostril. Gravity takes the water around the back of the nostril and drains out the opposite side of the nose. Then the same procedure is repeated on the opposite side. Although nasal irrigation promotes good sinus and nasal health, it can only be effective if purified, filtered, or boiled water is used. The use of unboiled or otherwise unsterilized water has proven to be an important risk factor in contracting Primary Amebic Meningoencephalitis (PAM).

Water samples collected from the kitchen faucet, shower, bathtub faucet, and bathroom sink faucet tested positive by direct PCR for N. fowleri (CDC).  Saline solution packets from 2 companies were prepared according to the manufacturers’ directions, and were tested at CDC. A saline solution packet was dissolved in 240 mL of distilled water to achieve a solution with 0.9% sodium chloride. Experiments were set up in duplicates in Costar 24-well Cluster flat-bottom plates with lids. N. fowleri amebae from the first case patient actively growing in modified Nelson medium were adjusted to obtain 500 amebae per milliliter of the saline solutions, and 2 mL of this solution was dispensed into each well and incubated in moist chambers at 37°C for 1, 4, and 18 hours; 2 mL of N. fowleri amebae (500 amebae per milliliter) in growth medium were set up as controls. At the end of each time period the amebae in the wells were photographed with an Olympus IMT-2 inverted microscope equipped with a digital camera. Test results revealed that the number of N. fowleri organisms did not appreciably decrease or degrade after 4 hours.   However, observation at 18 hours revealed that more than half of the amebae had died (cells rounding up or lifting off plate).

Nasal irrigation using saline solutions has been advocated as a safe, inexpensive method for managing chronic allergic rhinosinusitis. However, the PAM cases reported here and others in Australia and Pakistan involving direct or forceful application of tap water into the nasal passages (e.g., directing shower water up the nose, religious ablutions) indicate that there is a small risk associated with this practice when tap water is used.  Despite standardized instructions for the preparation of saline irrigation solutions, many patients use untreated tap water. The extremely rare, but typically fatal, risk of meningoencephalitis from Naegleria fowleri makes this a potential health hazard.


1. Garcia, L.S. 2016. Diagnostic Medical Parasitology, 6th Ed., ASM Press, Washington, D.C.

2.   Marciano-Cabral F, R MacLean, A Mensah, L LaPat-Polasko.  2003.  Identification of Naegleria fowleri in domestic water sources by nested PCR. Appl Environ Microbiol 69:5864-9.

3.   Dorsch MM, AS Cameron, BS Robinson. 1983. The epidemiology and control of primary amoebic meningoencephalitis with particular reference to South Australia. Trans R Soc Trop Med Hyg 77:372-7.

4.   Shakoor S, MA Beg, SF Mahmood, et al. 2011. Primary amebic meningoencephalitis caused by Naegleria fowleri, Karachi, Pakistan. Emerg Infect Dis 17:258-61.

5.   Siddiqui, R, NA Khan. 2014.  Primary amoebic meningoencephalitis caused by Naegleria fowleri: an old enemy presenting new challenges.  PLos Negl Trop Dis 2014 Aug 14;8(8):e3017. doi: 10.1371/journal.pntd.0003017

6.   Yoder, JS, S Straif-Bourgeois, SL Roy, TA Moore, GS Visvesvara, et al. 2012.  Primary amebic meningoencephalitis deaths associated with sinus irrigation using contaminated tap water.  Clin Infect Dis. 2012 Nov;55(9):e79-85. doi: 10.1093/cid/cis626. Epub 2012 Aug 22.


Each Quiz has a two section format: the first section will present the Quiz topic and the second section will provide a discussion of the answer and/or various options in response to the Quiz situation presented to the user. In some situations, there may be more than one correct response.

The content within this site is made possible through the extensive contribution of Lynne S. Garcia, M.S., MT(ASCP), CLS(NCA), BLM(AAB), F(AAM), Director, Consultantation and Training Services (Diagnostic Medical Parasitology and Health Care Administration). For additional information, she can be contacted at

Reference: Garcia, L.S. 2015. Diagnostic Medical Parasitology, 6th Ed., ASM Press, Washington, D.C.