Experimental Parasitology 99, 80–88 (2001) doi:10.1006/expr.2001.4652, available online at http://www.idealibrary.com on Entamoeba histolytica: Genetic Diversity of Clinical Isolates from Bangladesh as Demonstrated by Polymorphisms in the Serine-Rich Gene Patrick F. Ayeh-Kumi,* , ² , ‡ ,1 Ibnekarim M. Ali,§ ,1 Lauren A. Lockhart,* , ² , ‡ Carol A. Gilchrist,* , ² , ‡ William A. Petri, Jr.,* , ² , ‡ ,2 and Rashidul Haque§ *Department of Medicine, ² Department of Pathology, and ‡Department of Microbiology, University of Virginia Health System, Charlottesville, Virginia, 22908-1340, U.S.A.; and §International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh Ayeh-Kumi, P. F., Ali, I. M., Lockhart, L. A., Gilchrist, C. A., (SREHP); strain-specific gene (SSG); polymorphic DNA; tandem re- peats; nested polymerase chain reaction (PCR); endemic population; Petri, W. A., Jr., and Hague, R. 2001. Entamoeba histolytica: Genetic dithiothreitol (DTT); dimethyl sulfoxide (DMSO). diversity of clinical isolates from Bangladesh as demonstrated by polymorphisms in the serine-rich gene Experimental Parasitology 99, 80–88. The varied organ tropisms and clinical presentations of infection by Entamoeba histolytica have stimulated interest in the role of parasite genetic diversity in virulence. We investigated genetic diversity among 54 E. histolytica isolates from Bangladesh by analyzing polymorphism in the serine-rich gene by nested PCR on DNA extracted from stool INTRODUCTION and liver aspirate pus. We detected both size and restriction site poly- morphisms among the isolates within this endemic area. A combination of the nested PCR results and the AluI digestion of the PCR products examined yielded 25 distinct DNA banding patterns among the 42 The recent delineation of Entamoeba histolytica into two stool isolates and an additional 9 distinct patterns among the 12 liver genetically distinct species, the invasive pathogenic parasite abscess isolates. Approximately half of the isolates had unique poly- morphisms. Interestingly, the majority of E. histolytica from the liver E. histolytica and the noninvasive parasite E. dispar, is per- had polymorphisms which were not present in intestinal isolates from haps one of the major accomplishments in the field of amebi- the same geographic area. These data are consistent with the existence asis research (WHO 1997). It is believed that only E. histolyt- of genetic differences between E. histolytica which cause intestinal ica sensu stricto can cause intestinal and extraintestinal and those which cause hepatic disease. We conclude that there is genetic disease while E. dispar is known to be responsible for non- diversity within E. histolytica isolates from an endemic population as pathogenic colonization of the intestine. Global statistics on reflected in serine-rich E. histolytica protein gene polymorphism. The correlation of genetic differences with the pathogenic potential of E. the prevalence of E. histolytica infection indicate that 90% histolytica strains and the implications of genetic diversity for the of infected individuals remain asymptomatic carriers while immunoprophylaxis of amebiasis require further study.  2001 the other 10% develop clinically overt disease (Jackson et Elsevier Science al. 1985; WHO 1997; Haque et al. 1999). This observation Index Descriptors and Abbreviations: Entamoeba histolytica; E. might partly be due to differences in the pathogenic potential dispar; protozoa; parasite; amebiasis; serine-rich E. histolytica protein of infecting strains (Burch et al. 1991). Although colonization with E. dispar is suspected to be 3–10 times more frequent than that with E. histolytica in 1 These authors contributed equally to this work. asymptomatic individuals, only a few studies have directly 2 To whom correspondence should be addressed. Fax: (804) 924- 0075. E-mail: wap3g@virginia.edu. addressed this (Jackson et al. 1985; Gathiram and Jackson 0014-4894/01 $35.00 80  2001 Elsevier Science All rights reserved.