Selective media for Naegleria fowleri is
Correct Answer: Non-nutrient agar with E. coli
Description: Ans. c (Non-nutrient agar with with E.coli) (Ref Jawetz's Microbiology 24th/ Chapter 46)# Amebas can be readily cultured on nonnutrient agar plates seeded with Escherichia coli.FREE-LIVING AMOEBAS (CAUSING PRIMARY AMOEBIC MENINGOENCEPHALITIS)# Primary amebic meningoencephalitis: free-living soil amebas implicated are:- Naegleria fowleri,- Acanthamoeba castellanii,- Balamuthia mandrillaris, and- Hartmanella# Entry of Acanthamoeba into the CNS occurs from skin ulcers or traumatic penetration, such as keratitis from puncture of the corneal surface or ulceration from contaminated saline used with contact lenses.# Diagnosis is by microscopic examination of the CSF, which contains the trophozoites and red cells but no bacteria.# These soil amebas are distinguished by a large, distinct nucleus; by presence of contractile vacuoles and mitochondria (absent in Entamoeba); and by cysts that have a single nucleus and lack glycogen or chromatoidal bodies.# Acanthamoeba may encyst in invaded tissues, whereas Naegleria does not.# Rx with amphotericin B has been successful in a few cases, especaially diagnosis can be made quickly.Primary amebic meningoencephalitis (Naegleria Infections)# Primary amebic meningoencephalitis caused by Naegleria fowleri# Follows the aspiration of water contaminated with trophozoites or cysts or the inhalation of contaminated dust, leading to invasion of the olfactory neuroepithelium.# After an incubation period of 2-15 days# C/f: severe headache, high fever, nausea, vomiting, and meningismus develop. Photophobia and palsies of the third, fourth, and sixth cranial nerves are common.# The prognosis is uniformly poor: most patients die within a week.# Infection is most common in otherwise-healthy children or young adults, who often report recent swimming in lakes or heated swimming pools.# Diagnosis depends on the detection of motile trophozoites in wet mounts of fresh spinal fluid.# Antibodies to Naegleria spp. have been detected in normal adults; serologic testing is not useful in the diagnosis of acute infection.# Only a few survivors, treated with high-dose amphotericin B and rifampin, have been reported.Additional Educational Points:Common Culture Media in Mycology are:1. Sabouraud's glucose agar pH 5.42. Czapek-Dox medium3. Com meal agarNNN or Tobie's medium# In NNN only the promastigotes are found. L donovani usually grows slowly, the promastigotes forming tangled clumps in the fluid.# L tropica grows more quickly, promastigotes forming small rosettes attached by their flagella in the fluid, while# L braziliensis may produce a wax-like surface with fewer, smaller promastigotes.# In contrast, L mexicana produces rapid growth of large organisms in simple blood agar medium. In tissue cultures, intracellular amastigotes may occur in addition to the extracellular promastigotes.
Category:
Microbiology
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