Entamoeba moshkovskii infections in children, Bangladesh

Abstract

Entamoeba moshkovskii cysts are morphologically indistinguishable from those of the disease-causing species E. histolytica and the nonpathogenic E. dispar. Although sporadic cases of human infection with E. moshkovskii have been reported, the organism is considered primarily a free-living amoeba. No simple molecular detection tool is available for diagnosing E. moshkovskii infections. We used polymerase chain reaction (PCR) to detect E. moshkovskii directly in stool. We tested 109 stool specimens from preschool children in Bangladesh by PCR; 17 were positive for E. histolytica (15.6%) and 39 were positive for E. dispar (35.8%). In addition, we found that 23 (21.1%) were positive for E. moshkovskii infection, and 17 (73.9%) of these also carried E. histolytica or E. dispar. The high association of E. moshkovskii with E. histolytica and E. dispar may have obscured its identification in previous studies. The high prevalence found in this study suggests that humans may be a true host for this amoeba.

Figure 1

Entamoeba moshkovskii–specific nested SSU rDNA polymerase chain reaction (PCR) products. Odd- and even-numbered lanes represent undigested and XhoI-digested PCR products, respectively. Lanes 1/2, E. moshkovskii Laredo; lanes 3/4–5/6, DNA from stool samples. M, a 50-bp DNA ladder (Invitrogen Corp.).

Figure 2

Arg^TCT locus. Arg^TCT sequences from Entamoeba histolytica HM-1:IMSS (GenBank accession no. AZ535059), E. dispar SAW760 (GenBank accession no. AF 525284), E. moshkovskii Laredo (GenBank accession no. AF 525285), and MS15-3646 (GenBank accession no. AF525286) were aligned at the 5´(A) and 3´ (B) ends to design E. moshkovskii–specific primers. The EmR primer sequences are shown in italic and bold with E. moshkovskii–specific positions underlined. C. Schematic representation of Arg^TCT loci from E. histolytica HM-1:IMSS, E. dispar SAW760, and E. moshkovskii. Locations of the primers used in polymerase chain reaction amplification are indicated by small arrows, the tRNA genes are indicated by large arrows, and the short tandem repeats by shaded boxes (not to scale.)

Figure 3

EmR polymerase chain reaction products. Lane 1, Entamoeba moshkovskii Laredo; lane 2, E. moshkovskii ICDDRB:717; lanes 3–6, E. moshkovskii–positive stool DNA samples; lane 7, E. moshkovskii FIC; lane 8, E. histolytica HM-1:IMSS; and lane 9, E. dispar SAW760. M, a 100-bp DNA ladder (Promega).