Case report

報告者：邵郁鏵 時間： 941031

Present illness

A previously healthy 10-year-old boy was seen in July in the emergency department suffering from fever and a severe headache of several days' duration. He had vomited several times and complained of nausea and a runny nose.

The weather had been very hot, and the child had spent much of the summer swimming in a local pond. On exami-nation, the emergency room physician noted neck stiffness and performed a lumbar puncture.

Lab finding

Cerebrospinal fluid (CSF) was collected and sent to the laboratory for cell count, glucose and protein levels, bacterial culture, and a request to "rule out an amebic infection."

Lab finding

The white blood cell count of the CSF was 25,000 per mm3, with neutrophils pre-dominating. A small number of red blood cells were also present. The glucose level was decreased (<5 mg/dl), and the protein level was markedly elevated (600 mg/dl).

The Gram stain of the CSF showed many white blood cells but no bacteria. A wet mount microscopic examination revealed motile amebic trophozoites. A trichrome stain was made and revealed an ameboid form.

A diagnosis of meningoencephalitis was made. The child was admitted to the pedia-tric intensive care unit but died on the fourth day of hospitalization.

Question 1

Which ameba is likely to be responsible for the child's symptoms? What is the name of this infection?

奈格式阿米巴 (Naegleria fowleri) 短暫時期有鞭毛，且在宿主體內不形成cyst 、只有活動體，只在環境不好時變成 cyst 。 Acute( 急性 ) 感染常在特定淡水區域游泳之年輕人 , 由鼻子進入 , 透過篩板 , 經嗅神經 , 形成向心式腦膜腦炎 . 稱之為 PAM(primary amoebic meningo-meninginitis)

Question 2

What is the correlation between a "hot summer" and the child's illness?

游泳池的溫度約三十多度 C 它最喜歡 The means of determining whether a person has PAM are as follows :

1.Clinical signs and symptoms2.History of swimming in hot or

warm water3.Isolation of the amebas

Question 3

What are the stages in the life cycle of this parasite?

Naegleria.Flagellate

Naegleria.Trophozoite

Question 4

How is the diagnosis of this infection made in the laboratory?

wet mount microscopic examination

The direct wet mount is used primarily to detect motile protozoan trophozoites. These organisms are very pale and transparent, two characteristics that require the use of low light intensity. Protozoan organisms in a saline preparation will usually appear as refractile objects. If suspicious objects are seen on high dry power, allow at least 15 s to detect motility of slowly moving protozoa.

Heat applied by placing a hot penny on the edge of a slide may enhance the motility of trophic protozoa. Tapping on the coverslip can also stimulate the fluid to move; objects will roll over, thus providing a better view of the parasite or artifact. After the wet preparation has been thoroughly checked for trophic amebae, a drop of iodine can be placed at the edge of the coverslip or a new wet mount can be prepared with iodine alone.

A weak iodine solution is recommended; too strong a solution may obscure the organisms. The color should resemble "strong tea." Several types of iodine are available; D'Antoni's will be discussed here. Gram's iodine used in bacterial work is not recommended for staining parasitic organisms.

TRICHROME STAIN

The trichrome technique of Wheatley for fecal specimens is a modification of Gomori's original staining procedure for tissue. It is a rapid, simple procedure which produces uniformly well stained smears of the intestinal protozoa, human cells, yeast cells, and artifact material in about 45 min or less.

TRICHROME STAIN

The specimen usually consists of fresh stool smeared on a microscope slide that is immediately fixed in Schaudinn's fixative or PVA-preserved stool smeared on a slide and allowed to air dry. Although SAF- and MIF-preserved specimens can be stained with trichrome, there are other stains which are recommended for better overall results.

Question 5

How is this infection transmitted?

Question 6  

Which other ameba resembles this parasite and may cause a similar type of infection?

Acanthamoeba spp.棘阿米巴 (Acanthamoeba) 造成腦炎

Question 7

How can these two amebae be distinguished?

奈格式阿米巴 (Naegleria fowleri) 在組織中不會形成囊體 ; 奈格式阿米巴 (Naegleria fowleri) 短暫時期有鞭毛，且在宿主體內不形成cyst 、只有活動體，只在環境不好時變成 cyst 。

棘阿米巴 (Acanthamoeba) 在組織中形成囊體是 chronic( 慢性 ) 感染 , 由皮膚外傷 ,眼睛經週邊血液感染 , 會造成角膜炎 . 造成 GAE(granulomatous amoebic encephalitis) 是離心式的腦炎 .會形成星狀的囊體 , 有兩層的壁

Question 8

Which other infectious disease might be confused with this illness?

Bacterial meningoencephalitis

Chills and feverHeadacheNausea and vomitingBack painNeck stiffnessProstrationSharp shrill cry (meningeal cry in

children)Clouded, stupor or comaConvulsive seizure

Acute ill-looking Conscious change (confused, stuporour, or

semicomatose) Fever (may be occasionally normal at the

onset) Rapid pulse & respiratory rate Neck rigidity (positive Kernig and

Brudzinski signs, but may be absent in newborn, elderly, or comatous patient)

IICP Decreased DTR (but occasionally increased)

Kernig’s sign

讓病人平躺，將一支腳抬高，盡量使膝關節處成直角，用力把大腿往上扳（左圖），這個動作會拉扯整個脊椎；腦膜炎病人因為頭頸部疼痛、僵硬，所以會腰痛，腰向上挺起來，甚至會坐起來，釋放脊椎的牽扯力量。 Kerning’ sign 兩支腳都要做，因為有些反應有可能是因為坐骨神經痛所造成，這種情況下就只有一邊會有反應（一邊坐骨神經痛）；而腦膜炎一定是兩邊都會有反應（整條脊椎發炎）

Brudzinski’s sign

測試頸部是否僵硬。先讓病人平躺，再將病人的頸部向上扳，此時病人的膝部會向上彎曲，以減輕脊椎的疼痛。有些甚至不用看膝部是否有反應，只要把頸椎部向上扳，就可以感覺到整個頸部都很僵硬，甚至連肩膀都會被提起來。

Bacterial meningitis in different age group

Meningococcus (N. meningitidis)

Pneumococcus (Streptococcus pneumoniae)

Adult

Meningococcus (Neisseria meningitidis)

Adolescent

Haemophilus influenzaeInfant

Escherichia coliListeria monocytogenes

Neonatal

CSF STUDY

Question 9

Is this infection treatable?

Successful outcomes are reported with high-dose systemic and intrathecal amphotericin B.Survival is reported with intrathecal and systemic amphotericin B and miconazole, as well as rifampin and sulfisoxazole.

At present there is no satisfactory treatment for PAM. (Amphotericin B)PAM carries a mortality rate of approximately 95%, and patients usually die within 72 hours. Rarely, individuals survive after early recognition and aggressive therapy. 預防 : 不要跳水 , 久時間未使用的水龍頭要注意 , 不要把鼻子浸於水中

Reference

寄生蟲學科 : 詹益欣 M100 教學檔神經內科 : 尹居浩 M100 教學檔http://www.emedicine.com/med/topic1582.htm

Thanks for your attention !!!