A 15-year-old boy came back to his village after a vacation to his relatives. He developed severe headache and purulent nasal discharge and was diagnosed as acute bacterial meningitis. He died 5 days later. Which of the following is most likely etiological agent?
Ans. b. Naegleria fowleri (Ref: Harrison 19/e p1367, 18/e p1686)A 15-year old boy came back to his village after a vacation to his relatives. He developed severe headache and purulent nasal discharge and was diagnosed as acute bacterial meningitis. He died 5 days later. The above presentation is consistent with atypical free-living amoeba infection, most probably due to Naegleria fowleri.Naegleria fowleri:Naegleria prefers warm freshwater, and most cases occur in otherwise healthy children, who usually have swum in lakes or swimming pools during the previous 2 weeks.Naegleria enters the central nervous system via water inhaled or splashed into the nose, with trophozoites disrupting the olfactory mucosa, invading through the cribriform plate, and ascending via the olfactory nerves into the brain.Earliest manifestations are anosmia (usually perceived as alterations in taste), headache, nasal discharge, fever, photophobia, nausea, and vomiting.Death usually occurs within 7-10 days of the onset of symptomsLaboratory findings in the CSF resembles those in bacterial meningitis, with high opening pressures, low glucose levels, high protein concentrations, and elevated polymorphonuclear cell-predominant white blood cell counts.Diagnosis of PAM is based on the finding of motile Naegleria trophozoites in wet mounts of freshly obtained cerebrospinal fluid (CSF).Naegleria fowleri* Naegleria (the 'brain-eating amoeba') is the causative agent of primary amebic meningoencephalitis (PAM)Q.* Pathogenic free living amoebaeQSpread of Infection:* Naegleria prefers warm freshwater, and most cases occur in otherwise healthy children, who usually have swum in lakes or swimming pools during the previous 2 weeksQ.* Naegleria enters the central nervous system via water inhaled or splashed into the nose, with trophozoites disrupting the olfactory mucosa, invading through the cribriform plate, and ascending via the olfactory nerves into the brainQ.Pathology:* Hemorrhagic necrosis of brain tissue (often most prominent in the olfactory bulbs)Q* Evidence of increased intracranial pressureQ* Scant purulent material that may contain a few amoebas* Marked leptomeningitisQClinical Features:* Earliest manifestations are anosmia (usually perceived as alterations in taste), headache, nasal discharge, fever, photophobia, nausea, and vomitingQ.* Cranial nerve palsies, especially of the 3rd, 4th and 6th nerves, are documented and rapid progression of disease, with seizures and comaQ* Death usually occurs within 7-10 days of the onset of symptomsQDiagnosis:* Diagnosis of PAM is based on the finding of motile Naegleria trophozoites in wet mounts of freshly obtained cerebrospinal fluid (CSF)Q.* Laboratory findings in the CSF resembles those in bacterial meningitis, with high opening pressures, low glucose levels, high protein concentrations, and elevated polymorphonuclear cell-predominant white blood cell countsQ.* PAM should be suspected in any patient who has an appropriate history and purulent meningoencephalitis with negative gram stains, negative antigen detection and PCR tests for other pathogens, and negative bacterial culturesQ.Treatment:* The few survivors who have been reported were treated with high-dose amphotericin B and rifampin in combinationQ.Prognosis:* Unfortunately, the prognosis for PAM is dismalQ.
Entamoeba histolytica
Naegleria fowleri
Toxoplasma gondii
Plasmodium falciparum
C.N.S.