Gohta Masuda

Remarkable Genetic Polymorphism among Entamoeba histolytica Isolates from a Limited Geographic Area

ABSTRACT In order to understand genetic polymorphisms among Entamoeba histolytica strains in a limited geographic area and among restricted social populations, we studied nucleotide polymorphism in DNA regions that do not encode proteins (locus 1-2 and locus 5-6) and in genes coding for chitinase and for serine-rich E. histolytica protein. Thirty E. histolytica isolates from domestically infected Japanese amebiasis patients (male homosexuals and residents in institutions for the mentally handicapped) and four reference strains were examined. PCR revealed remarkable polymorphisms in both the number and size of the PCR fragments containing these loci. Polymorphisms in lengths, types, and numbers of internal repeat units were observed in locus 1-2 and the repeat-containing region of serine-rich E. histolytica protein among the Japanese isolates. In contrast, polymorphism at locus 5-6 was observed almost exclusively in the number of repeats of a 16-nucleotide unit. The repeat-containing region of chitinase appeared to be the least polymorphic among the four loci with a single dominant genotype representing 66% (20 out of 30) of all of the isolates. Isolates obtained from male homosexuals showed a more complex genetic polymorphism than those from residents in institutions. Considering all four polymorphic loci together, all 19 Japanese isolates from male homosexuals were distinct. In contrast, all isolates obtained from mass-infection cases at a single institution had an identical genotype, suggesting that these cases were caused by a single E. histolytica strain. No significant correlation was found between genotypes and zymodemes or between genotypes and clinical presentations, e.g., colitis or liver abscess. Certain genotypes were observed with higher frequencies in male homosexuals or residents of institutions. These data indicate that genotyping of the E. histolytica isolates by using these four polymorphic loci could serve as a tool to fingerprint individual isolates. We propose that genotyping of ameba isolates should help to determine geographic origins of isolates and routes of transmission.

Evaluation of Recombinant Fragments of Entamoeba histolytica Gal/GalNAc Lectin Intermediate Subunit for Serodiagnosis of Amebiasis

ABSTRACT We have recently identified a 150-kDa surface antigen of Entamoeba histolytica as an intermediate subunit (Igl) of galactose- and N-acetyl-d-galactosamine-inhibitable lectin, which is a cysteine-rich protein consisting of 1,101 amino acids (aa) and containing multiple CXXC motifs in amino acid sequences. In the present study, full-length Igl except for the signal sequences (aa 14 to 1088) and three fragments of Igl—the N-terminal part (aa 14 to 382), the middle part (aa 294 to 753), and the C-terminal part (aa 603 to 1088)—were prepared in Escherichia coli, and the reactivity of these recombinant proteins with sera from patients with amebiasis was examined by means of enzyme-linked immunosorbent assay (ELISA). Sera from 57 symptomatic patients with amebic liver abscess or amebic colitis, sera from 15 asymptomatic cyst passers, sera from 40 individuals with other protozoan infections, and sera from 50 healthy controls were used. The sensitivity and specificity of the recombinant full-length Igl in the ELISA were 90 and 94%, respectively. When three fragments were used as antigens in the ELISA, the sensitivities were 56% in the N terminus, 92% in the middle part, and 97% in the C terminus. The specificities of the three antigens were 96% in the N terminus and 99% in both the middle and C-terminal fragments. These results demonstrate that Igl is well recognized in not only symptomatic but also asymptomatic patients with E. histolytica infection and that the carboxyl terminus of Igl is an especially useful antigen for the serodiagnosis of amebiasis.

Clinical and Bacteriological Profiles of Patients with Typhoid Fever Treated during 1975–1998 in the Tokyo Metropolitan Komagome Hospital

Patients with typhoid fever presenting to the Tokyo Metropolitan Komagome Hospital during the period 1975–1998 were retrospectively investigated. All cases were diagnosed by a positive culture for Salmonella typhi in either of their clinical specimens. Of the total number of 130 patients, 57% contracted the disease abroad; this population increased in later years as the total numbers of cases decreased. The period from disease onset to diagnosis averaged 14 days with 20% of the cases requiring over three weeks to establish a diagnosis. As for symptomatology relative bradycardia was seen in less than half of the cases, and rose spots or splenomegaly in less than one third. A positive blood culture was the most frequent test establishing the diagnosis followed by a positive stool culture. Intestinal bleeding was recognized in as many as 35 cases (27%) and even intestinal perforation occurred in two cases (1.5%). Chloramphenicol was most commonly employed during the early study period, however, during the late period it was replaced by fluoroquinolones. The clinical cure rate was 98% with regimens that include fluoroquinolones/quinolone; however it was 87% with the other antimicrobial regimens. Bacteriological relapse occurred in 25% of the non‐fluoroquinolone group while only in 2.0% in the fluoroquinolone/quinolone group. Four strains of Salmonella typhi that were multi‐resistant to chloramphenicol, ampicillin and cotrimoxazole were isolated in travelers from Asia. Early diagnosis by appropriate bacteriological examination regardless of classical symptomatology should be stressed and the use of fluoroquinolones is warranted in the treatment of typhoid fever.

A case of AIDS-related hepatic Kaposi's sarcoma

In Japan, Kaposis sarcoma (KS) is a very rare neoplasm. However, it does occur as one of the complications in patients with acquired immunodeficiency syndrome (AIDS). AIDS-related KS commonly involves the skin, lymph nodes, and gastrointestinal tract. Hepatic KS is sometimes observed in AIDS patients at autopsy, but it is very rarely diagnosed during life. We report a case of hepatic KS in an AIDS patient, detected by ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI) during life and proven at autopsy. Abdominal US revealed multiple hyperechoic tumors along the portal vein. CT scan showed low density and delayed enhancement by contrast material. These tumors were revealed as a low intensity area on a T1-weighted image of MRI and as a high intensity area on T2-weighted and proton density images. US, CT scan, and MRI revealed characteristic findings of hepatic KS. These procedures are very useful for the diagnosis of hepatic KS. To our knowledge, this is the first report of hepatic KS in Japan.