2. 52 VALENZUELA AND OTHERS
Figure 1. A, Thoracic x-ray taken during patient admission. The image shows elevation of the hemidiaphragm. B, Computed tomography (CT)
scan showing an image of both large abscesses in the left and right hepatic lobules.
After electrophoresis, the gels were photographed for our E. histolytica HM1:IMSS is shown in Figure 2A. Sequences of
records. The PCR products were purified using the GFX kit both left and right lobules abscesses are shorter than the E.
(Amersham Pharmacia Biotech, Sao Paulo, Brazil) and then histolytica HM1:IMSS strain, there is also a nucleotide change
sequenced at the University of Arizona (Genomic Analysis & (G by A) in position 109 on the HM1:IMSS strain (Figure 2B).
Technology Core, Tucson, AZ). The sequences were aligned The sequence of Ehcht gene in the left hepatic lobule abscess
with the reported sequences of E. histolytica present in the is identical to genotype H reported previously in ALA cases
Gen Bank data base (Figure 2A and B). in Mexico (Gen Bank accession no. EF-445962). However,
the Ehcht gene sequence obtained in the right hepatic lobule
abscess is identical to the one on NIH-200 and K1 E. histolyt-
RESULTS AND DISCUSSION
ica strains reported by Ghosh and others.4
In the present work, we report a patient with ALA who Translation of the nucleotide sequences into amino acid
developed two independent abscesses located in the right and sequences and the corresponding alignment is shown in
left hepatic lobules (Figure 1A and B). The clinical findings Figure 2B and correlates with the nucleotide sequences men-
were coincident with the presence of high levels of circulating tioned earlier.
anti-amebic antibodies, as detected by ELISA. Together, these Even though simultaneous intestinal infections by E. his-
results point to an amebic etiology for the liver abscess (OD tolytica and E. dispar have been previously reported,17,19–21 this
at 490 nm of 1.8).15,16 was the first report that showed amebic infection by more than
Entamoeba histolytica was confirmed as the causative agent one genetic variant of the E. histolytica species in the same
by PCR analyses of the drainage material from both abscesses. patient. This phenomenon has been described for other par-
Samples from the two abscesses contained fragments of the asitic infections, such as trypanosomiasis, leishmaniasis, and
Ehcht gene, the amplified region was located between the sig- malaria.22,23
nal sequence and the catalytic site of the protein, which has It is known that ALA occurs without any colitis symptoms
heptapeptide repetitive sequences rich in hydrophilic amino and without any detectable parasites in the colon. On the
acids (Ser, Glu, Ssp, Hys, and His). However, some hydro- basis of these clinical observations, Charmot24 emphasized
phobic amino acids (Pro, Val, and Ile) were also present in the possibility that E. histolytica hepatotropic strains may
the sequences.18 The alignment of the respective nucleotide exist by mentioning that “the localization, heterogeneity, and
sequences of the PCR products obtained from material of the experimental data associated with clinical expression sug-
both left and right hepatic lobules and the reported sequences gest the existence inside the species E. histolytica of various
in the Gen Bank database (accession no. XM 647113.1) for strains: non-pathogenic one, invasive for the intestine mucous
membrane ones, and invasive for liver tissue ones.” Recently,
Ali and others25 genotyped E. histolytica strains from fecal and
Table 1 aspirated ALA samples of the same patient and demonstrated
Primer sequences the existence of co-infection by different types of strains. Their
Primer Sequence results, together with our finding, have opened a series of pos-
CHI5 GAAS*AACAGAAGGAACACCAGG sible explanations for this phenomenon. Ali’s group used poly-
CHI-Eh/Ed3 TCTGTATTGTGCCCAATT morphic intergenic regions (short tandem repeats) associated
Hsp 1 GAGTTCTCTTTTTATACTTTTATATGTT with tRNA genes as the target for genotyping the strains. The
Hsp 2 ATTAACAATAAAGAGGGAGGT authors mentioned that their results were compatible with a
StgaD-H5 AAATCCTGCCACTGTCGTAA
StgaD-H3 AATCCCCGTTGAAGAGTTCT possible new infection during the lapse between the first inoc-
SQ 5 GTGGTCTAAGGCGTGTGACT culum and the development of ALA symptoms, an account that
SQ H3 GTGGGACCACTTTTTATACCTA is reasonable in endemic regions. Another possible explanation
*S=C+G is the existence of ecologic niches in endemic environments in
3. TWO DIFFERENT EhCHT GENOTYPES IN AN AMEBIC LIVER ABSCESS 53
Figure 2. A, Nucleotide sequence alignment of the polymerase chain reaction (PCR) amplification products amplified by CHI primers. The
DNA was independently extracted from the drainage material of the left and right hepatic lobule abscesses. B, Alignment of the deduced amino
acid sequences obtained from the PCR products of the Eh chitinase gene. The DNA from the E. histolytica HM1:IMSS strain was simultaneously
studied as a reference strain. The corresponding heptapeptides were marked in color. This figure appears in color at www.ajtmh.org.
which genetically heterogeneous Entamoeba species could Medicina Interna, Hospital General del Estado, Hermosillo Sonora,
exist (i.e., E. histolytica and E. dispar species, as was previously México, Boulevard Luis Encinas y Reyes Col. Centro. CP 83000,
Tel/Fax: +52 662 2121422.
mentioned, or intraspecies genetic variants).6,19–21
Another explanation mentioned by Ali and others is that a Reprint requests: Cecilia Ximénez, Departamento de Medicina
recombination event may have occurred on the parasite DNA Experimental, Facultad de Medicina, UNAM, Dr. Balmis 148, Col.
Doctores, CP 06726, México D.F., México, Tel: +5255-56-23-26-66,
during the migration process from the intestine to the liver.25 Fax: +5255-56-23-26-79, E-mail: cximenez@servidor.unam.mx.
These events are relatively frequent in multiple copy genes,
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