This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'A patient presents with a headache, high fever and meningismus. Within 3 days he becomes unconscious. Most probable causative agent \nSelect and explain. \nA. Naegleria fowleri, B. Acanthamoeba castellanii, C. Entamoeba histolytica, D. Trypanosoma cruzi', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Amongst the given options Naegleria and Acanthamoeba cause amoebic encephalitis.\n\n“The prognosis of Naegleria encephalitis is uniformly poor, most patients die within a week” -------Harrison “Acanthamoeba encephalitis follows a more indolent course”.\n--------Harrison\n\n\xa0So, amongst the given options Naegleria causes most fatal amoebic encephalitis.\n\nNaegleria fowleri\n\n\xa0It is a free-living amoeba\n\xa0Exists in three forms - Amoeboid trophozoite, Biagellate trophozoite, Cyst (Never forms in the human body)\n\xa0Modes of transmission - Human primarily contact the infection by swimming in contaminated water.\n\nThe amoeboid trophozoite enters the human body through the nasal mucosa and migrates to the brain along the olfactory nerve and blood vessels.\nSome infections result from inhalation of cysts.\n\n\xa0Clinical features (primary amoebic meningoencephalitis) Common in young adults and children.\n\nIncubation period →2-15 days (5 days) A headache, high fever, nausea, vomiting, meningismus. Cranial nerve palsies —» 3rd, 4th\xa0and 6th. Most patients die within a week (95%).\nN. fowleri also causes humidifier fever, a form of allergic alveolitis resulting from inhaling air from air-coolers.\n\xa0Diagnosis - Detection of motile amoeboid trophozoites in wet mounts of C.S.F.\n\xa0Treatment - High doses of amphotericin B and rifampicin.\nAcanthamoeba -\xa0It is a free-living amoeba\n\n\xa0Acanthamoeba culbertsoni species is most common,\n\n\xa0Exists in two stages - Trophozoite, Cyst\n\n\xa0The appellate stage is absent\n\xa0Modes of transmission - Through contamination of traumatized skin or eye Inhalation.', 'role': 'assistant'}]