TY - CHAP M1 - Book, Section TI - Chapter 348. Free-Living Amebic Infections A1 - ALI, Ibne Karim M. A1 - Petri Jr., William A. A2 - Rudolph, Colin D. A2 - Rudolph, Abraham M. A2 - Lister, George E. A2 - First, Lewis R. A2 - Gershon, Anne A. Y1 - 2011 N1 - T2 - Rudolph's Pediatrics, 22e AB - Amebiasis and infections due to Entamoeba species are discussed in Chapter 341. The ubiquitous, free-living amoebae of the genera Naegleria, Balamuthia,Acanthamoeba, and Sappinia are the etiologic agents of rare infections of the central nervous system and eyes.1Naegleria fowleri is the agent of primary amebic meningoencephalitis; Acanthamoeba and Balamuthia cause granulomatous amebic meningoencephalitis; and Acanthamoeba also can infect the eye, resulting in amebic keratitis.2-4 Recently, Sappinia diploidea, another free-living amoeba that is normally found in soil contaminated with herbivore feces, has been identified as causing encephalitis in a healthy young man.5Naegleria, Balamuthia,Acanthamoeba, and Sappinia have trophozoite and cyst stages; in addition, Naegleria has a flagellate stage. For Naegleria, only trophozoites are found in tissues. Naegleria trophozoites are 10 to 30 μm in diameter and have a clear nucleus with a prominent central dense nucleolus and cytoplasmic pseudopodia. Acanthamoeba and Balamuthia trophozoites are of similar size and appearance to Naegleria, but the cyst form of these parasites may also be observed in tissue.1,6Sappinia trophozoites are 40 to 80 μm in diameter and have an ovoid or oblong shape. They appear to be flattened with occasional wrinkles on the surface, and food vacuoles are seen in cytoplasm. The mature cysts are 15 to 30 μm in diameter and are round. They have two adjoining nuclei.1 Unequivocal identification of these amoebae is not routine, and specimens should be referred to a qualified protozoologist for confirmation. SN - PB - The McGraw-Hill Companies CY - New York, NY Y2 - 2024/03/29 UR - accesspediatrics.mhmedical.com/content.aspx?aid=7031718 ER -