CASE HISTORY
Brianna,a 22-year-old college student,had returned recently from spring break at the beach in Acapulco,Mexico.She presented at the college clinic complaining of severe abdominal cramps and fever.She also had nausea and bloody diarrhea with mucus.The nurse practitioner collected stool samples and sent them to the laboratory for analysis.Cultures were negative for bacterial pathogens.A trichrome stain was performed,revealing amebas of the trophozoite (active feeding)stage.The stained amebas contained ingested red blood cells.The appearance of the amebas was characteristic of Entamoeba histolytica,the cause of amebic dysentery (bloody diarrhea),or intestinal amebiasis.Brianna was treated with paromomycin (an aminoglycoside that inhibits protein synthesis)for seven days,and her symptoms resolved.
Stained amebas isolated from Brianna's fecal sample indicated amebas in the trophozoite stage.At what life cycle stage did she likely ingest the parasite? Why are other forms less likely?

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The Answer of CASE HISTORY
Brianna,a 22-year-old college student,had returned recently from spring break at the beach in Acapulco,Mexico.She presented at the college clinic complaining of severe abdominal cramps and fever.She also had nausea and bloody diarrhea with mucus.The nurse practitioner collected stool samples and sent them to the laboratory for analysis.Cultures were negative for bacterial pathogens.A trichrome stain was performed,revealing amebas of the trophozoite (active feeding)stage.The stained amebas contained ingested red blood cells.The appearance of the amebas was characteristic of Entamoeba histolytica,the cause of amebic dysentery (bloody diarrhea),or intestinal amebiasis.Brianna was treated with paromomycin (an aminoglycoside that inhibits protein synthesis)for seven days,and her symptoms resolved.
Stained amebas isolated from Brianna's fecal sample indicated amebas in the trophozoite stage.At what life cycle stage did she likely ingest the parasite? Why are other forms less likely?

CASE HISTORY Brianna,a 22-Year-Old College Student,had Returned Recently from Spring Break at Break