Evidence for a link between locus R-R sequence type and outcome of infection with Entamoeba histolytica

Abstract

The results of Entamoeba histolytica infections range from asymptomatic colonization to variable disease outcomes. However, markers that may predict infection outcomes are not known. Here, we investigated sequence types of a non-coding tRNA-linked locus R-R to identify surrogate markers that may show association with infection outcomes. Among 112 clinical samples--21 asymptomatic, 20 diarrhoea/dysentery and 71 liver abscesses--we identified 11 sequence types. Sequence type 5RR was mostly associated with asymptomatic samples, and sequence type 10RR was predominantly associated with the symptomatic (diarrhoea/dysentery and liver abscess) samples. This is the first report that identifies markers that may predict disease outcomes in E. histolytica infection.

FIG. 1

Schematic representation of locus R-R sequence types and their distribution in clinical samples. The tRNA gene sequence is shown with arrow and the short tandem repeat sequences (STRs) are shown with colored bars. Three blocks (Block A, Block B and Block C) of STRs showed variability in number of repeats. Among all 112 samples, 11 different locus R-R sequence types were detected. *Sequence type 7RR was not detected in this study population although it was previously identified in a Japanese E. histolytica strain from an individual with unknown clinical manifestation (12). Three most common sequence types (5RR, 6RR, and 10RR) were shown in bold fonts. In the clinical distribution: A = asymptomatic; D = diarrhea/dysentery; LA = liver abscess; and N represents the total number of samples in a particular clinical population. Part of this figure is drawn similar to the Fig 4 in (12).

FIG. 2

Percent frequency of the 3 major locus R-R sequence types among the clinical samples. The sequence type 5RR is significantly associated with the asymptomatic sample group (P-values between asymptomatic & diarrhea/dysentery, asymptomatic & diarrhea/dysentery plus liver abscess sample groups are 0.0148 and 0.0241, respectively). In contrast, the sequence type 10RR is significantly associated with the symptomatic sample group (i.e. diarrhea/dysentery and / or liver abscess sample groups) (P-values between asymptomatic & diarrhea/dysentery, asymptomatic & liver abscess, and asymptomatic & diarrhea/dysentery plus liver abscess sample groups are 0.0089, and 0.0198, and 0.0123, respectively). The sequence type 6RR is distributed almost evenly across all clinical sample groups. A = asymptomatic; D = diarrhea/dysentery; and LA = liver abscess.