ASYMPTOMATIC INTESTINAL COLONIZATION BY PATHOGENIC ENTAMOEBA-HISTOLYTICA IN AMEBIC LIVER-ABSCESS - PREVALENCE, RESPONSE TO THERAPY, AND PATHOGENIC POTENTIAL

Since the application of isoenzyme electrophoresis to the study of Ent amoeba histolytica, the prevalence and natural history of asymptomatic intestinal colonization in patients with amebic liver abscess (ALA) h as not been addressed. We prospectively evaluated this enteric phase i n 50 patients with ALA, using two dosage regimens of metronidazole. Th e overall prevalence of asymptomatic colonization was 72% (36/50). All these isolates, without exception, proved to express pathogenic zymod emes. Despite a 100% clinical response of the hepatic lesions, failure to eradicate the organism from the bowel occurred in 20 of these 36 s ubjects. During longitudinal posttreatment surveillance, three carrier s returned with second bouts of invasive disease: one with dysentery a nd two with liver abscesses. Thus, in patients with ALA, there is a hi gh prevalence of intestinal colonization with exclusively pathogenic s trains, and treatment with metronidazole frequently results in a conti nued carrier state. These carriers have a propensity for developing re current invasive disease and constitute a public health hazard.