Serological study of Toxoplasma gondii in kidney recipients.

Toxoplasma gondii IgG antibodies were determined in 200 kidney recipients by the Sabin-Felmand dye test. Twenty-two (11%) cases were positive for antibody detection. There was a statistically significant difference in the history of taking under-cooked meat, between the number of sero-positive cases and that of sero-negative subjects (63.6% vs 28.8%, p = 0.02). No such significant difference was evident regarding cat ownership (13.6% vs 22.0%, p = 0.3). Sixteen (72.6%) of the 22 subjects with positive Tgondii antibody had undergone kidney transplantation less than one year ago during which a high dose of immunosuppressive drugs were prescribed. The remaining six (27.3%) cases had had transplantation more than one year ago and were on a lower dosage of immunosuprresants. Toxoplasma reactivation seemed to be higher in the former group, which should thus be closely followed-up. Preventive chemoprophylaxis should be considered if there is any indication of toxoplasma reactivation. Since there have been occasional reports of donor-to-host transmission of toxoplasmosis in kidney transplant recipients, serological screening of toxoplasma antibody in kidney donors is advisable. Potential donors with positive toxoplasma antibody should be rejected; but if that is unavoidable, 6-week prophylactic treatment of primary infection in kidney recipients should be administered.

Predictive value of latex agglutination test in serological screening for Toxoplasma gondii.

The predictive value of commercial latex agglutination kit (Toxo-Screen DA, bioMerieux) was assessed for use as screening test for Toxoplasma IgG antibody. The sensivity and specificity were also compared with those of the reference standard Sabin-Feldman dye test. Five hundred serum samples were collected from 200 blood donors and 100 each from pregnant women, kidney recipients and HIV infected persons. Eighty (16.0%) out of 500 subjects were positive for Toxoplama IgG antibody by Toxo-Screen DA (bioMerieux) compared with 57 (11.4%) by Sabin-Feldman dye test. The sensivity and specificity of Toxo-Screen DA (bioMerieux) were 100% and 94.8 % respectively which were similar to previous reports from the area of high prevalence of Toxoplasma infection. In present study the positive predictive value of Toxo-Screen DA (bioMerieux) was only 71.3%. The latex agglutination test should be considered as a screening test for Toxoplasma antibody, especially by small laboratories in remote area due to its availability, simplicity, sensitivity and specificity. However, because of its moderate positive predictive value, the test should be used with caution in screening immunocompromised patients and pregnant women living in areas with low prevalence of Toxoplasma infection. Since the number of false seropositive cases would be relatively higher than in a highly prevalent area, confirmation by the dye test would be needed.

Toxoplasma gondii antibody in HIV-infected persons.

Toxoplasmosis in an immunocompromised host was not documented in Thailand until 1992 when HIV/AIDS infection became pandemic. Patients with toxoplasmic encephalitis and cerebral abscess were recorded, particularly from the northern part of the country. However, data on the prevalence of the disease in HIV/AIDS patients is not yet available. In this study the authors determine the prevalence of T. gondii antibody in HIV persons. During a two-year period 312 serum samples of which 190 were HIV positive and the remaining samples were negative for HIV were tested. In the HIV positive group, 44 samples (23.2%) were positive for toxoplasma IgG antibody, whilst in the HIV negative group 36 samples (29.5%) were positive. All antibody titres found were not higher than 1:64. There is no significant difference of toxoplasma IgG antibody in HIV positive and HIV negative persons (p = 0.25). Among the HIV positive and T. gondii antibody positive group, 19 out of 44 persons (43.2%) had symptoms and signs of acute toxoplasmosis involving the eye and/or the central nervous system. Due to the high reactivation rate, the authors propose that all HIV-infected persons should be tested for T. gondii antibody and prophylactic treatment of opportunistic infection from T. gondii should be considered in those with positive results.

Toxoplasma gondii antibody in pregnant women with and without HIV infection.

One thousand two hundred pregnant women were examined for Toxoplasma gondii antibody with the objective of identifying the prevalence and risk factors of the disease. By using Sabin-Feldman Dye test, the prevalence of IgG to Toxoplasma gondii was 13.2%. In this study 19 cases (1.6%) were anti-HIV seropositive. Between HIV-seropositive and HIV-seronegative pregnant women, antibody rates to T. gondii were 21.1% and 13.1% respectively, however, the statistical comparison could not be done due to the very few subjects in the former group (n=4). Concerning the risk factors, among those who had no cat in their house, the prevalence of T. gondii antibody were significantly different between under-cooked and properly-cooked meat consumers (19.5%; and 9.6%; odds ratio=2.28, 95% confidence interval). And when under-cooked meat consumers were excluded, the antibody to T. gondii between two groups (having and not-having cat in the house) were also found the significantly different (31.8% and 19.3%; odd ratio=1.96, 95% confidence interval). In conclusion, consuming under-cooked meat and having a cat in the house, both are risk factors of transmission of toxoplasmosis. Further study with more subjects in HIV-infected pregnant women who had antibody to T. gondii, will be helpful for confirmation of the difference with respect to the non HIV-infected group.

Monoclonal antibody-based ELISA for the detection of circulating Entamoeba histolytica antigen in hepatic amebiasis in hamsters (Mesocricetus auratus).

Circulating amebic antigens were determined by using a sandwich ELISA with specific monoclonal antibody in the sera of 35 group I hamsters, 7 of which were sacrificed at intervals after hepatic inoculation with 500,000 axenically grown HM:1:IMSS strain of E. histolytica trophozoites, 7 group II infected hamsters in which metronidazole treatment was given and 18 group III uninfected controls. Amebic antigenemia was demonstrated in 5 of 7 (71.4%), 6 of 7 (85.7%), 7 of 7 (100%), 7 of 7 (100%) and 7 of 7 (100%) of group I hamsters on days 5, 10, 15, 20 and 30 of infections respectively, whereas 6 of 7 (85.7%) of group II hamsters were weakly positive, one was negative and all 18 group III hamsters were negative. The sensitivity of the assay was 100% after the animals were infected 15 days onwards. The level of antigenemia in hamsters of group I with abscess was significantly higher than those of the same group without abscess (p < 0.05). Absence or reduction of antigenemia after treatment could be interpreted to mean a positive test of cure and favorable therapeutic response. The MAb-PAb-based ELISA for the detection of circulating E. histolytica represents a simple and sensitive diagnostic test for invasive amebiasis in hamsters. Application of this test in amebic liver abscess patients should be of diagnostic value for indication of present infection or test of cure after successful treatment.

Cloning of Thai strain Giardia intestinalis.

Axenic cultures of Giardia intestinalis trophozoites were successfully established from human fecal specimens and rectal swabs from dogs using sucrose gradient centrifugation to separate the cysts from fecal material, the excystation method of Robert-Thompson et al. and culture of the preparation in TYI-S-33 medium supplemented with human serum, vitamin mixture and piper acillin and amikacin antibiotics, respectively. Fungal contamination could be controlled by amphotericin B at 10 micrograms per ml of medium. Clones of the parasites were obtained using a combination of dilution method and micromanipulation technique.

Pattern of antibodies in toxoplasmosis of pregnant women and their children in Thailand.

The latex agglutination test for toxoplasmosis was performed on 690 blood samples collected from the Veterans and Bang Bua Thong Hospitals in Bangkok. Blood samples were collected in the first- and the third-trimester from pregnant women and from the cord blood. The seroprevalence of toxoplasmosis in the first trimester was 13.14%, 13.60%; in the third trimester was 12.21%, 9.43% and in the cord blood 7.18% and 13.04% for the Veterans Hospital and Bang Bua Thong Hospital, respectively. There was no significant difference between the prevalence of toxoplasmosis for each type of blood from both hospitals. The average prevalence of toxoplasmosis for Thai pregnant women in the first- and third-trimester was 13.38% and 11.41%, respectively, and that for the cord blood was 9.01%. Congenital toxoplasmosis occurred in children of untreated mothers who were seropositive or seronegative in the third-trimester, the infection rates of the fetus being 46.67% and 8.13% respectively.

In vitro studies on the sensitivity of local Entamoeba histolytica to anti-amoebic drugs.

The in vitro activity of drugs, namely dehydroemetine, ornidazole, metronidazole and tinidazole were determined against the locally isolated strains of E. histolytica in Thailand. The test was performed in liquid monophasic medium, i.e. liver marmite serum medium. In all, locally isolated strains from thirty hosts studied, the minimal inhibitory concentration (MIC) for dehydroemetine ranged from 0.125 to 1 microgram/ml, ornidazole ranged from 0.0625 to 0.25 microgram/ml, metronidazole ranged from 0.0625 to 0.125 microgram/ml, and tinidazole ranged from 0.0625 microgram/ml to 0.25 microgram/ml. The MIC of dehydroemetine was significantly different from ornidazole, metronidazole and tinidazole. Metronidazole was superior to that of dehydroemetine but was not significantly different among ornidazole, metronidazole and tinidazole.

In vivo and in vitro studies of tinidazole in Trichomonas vaginalis infection.

A total 787 patients with complaints of vaginal discharges were examined, of which 106 patients were found to be positive for Trichomonas vaginalis by the normal saline method, and 114 patients were positive by the culture method. In the in vivo series, 55 patients were treated with a single dose of 1.8 gm of tinidazole, and with a follow-up examination 7 days there after. For the in vitro study 55 swab specimens were cultured to study the tinidazole sensitivity of Trichomonas vaginalis. The survival of Trichomonas vaginalis at each concentration of tinidazole was presented as a cumulative frequency. At the concentration of 1 microgram/ml, none of the organisms were killed; but at the concentration of 6 micrograms/ml, the mortality rate was 100%. In the in vivo series a 100% cure rate was obtained with tinidazole with no side effects, and in vitro series the mean minimum trichomonicidal concentration (MCC) at 24 hours was 3.76 +/- 1.25 micrograms/ml, with the range of 2--6 micrograms/ml. These studies revealed the sensitivity of Trichomonas vaginalis to tinidazole in Thailand and that tinidazole at a single oral dose of 1.8 gm perferably after a meal is effective, safe and cheap for the treatment of Trichomonas vaginalis.

A study on the diagnostic methods for Trichomonas vaginalis infection.

A comparison of the sensitivity of the wet smear, Papanicolaou's stained smear, and culture in Cystein-Peptone-Liver-Maltose (CPLM) medium for the diagnosis of T. vaginalis infection was undertaken in 1, 197 female subjects, both with and without gynaecological disorders. The wet smear method gave 15.5% positives, culture method, 16.5% positives and Papanicolaou's stained smear 6.7% positives. All positive cases by Papanicolaou's method or wet smear method were positive by the culture method. These findings indicate that the wet smear and culture in CPLM medium were better than the Papanicolaou's method.

In vivo and in vitro studies of quinine sensitivity of Plasmodium falciparum in Thailand.

Forty-four patients with falciparum malaria were studied. Nine patients were given quinine orally at a daily dose of 1.5 gm base for a period of 14 days. The mean parasite clearance in all 9 patients was 3.3 days, and none had recrudescence in follow-up examinations for 31 days. The in vivo study of these 9 patients showed sensitivity to quinine which correlated with the in vitro test, with concentration of quinine base 2.5-5.8 microgram/ml of blood that inhibited the maturation of Plasmodium falciparum parasites. The results of the in vitro test of 35 patients showed concentrations of quinine base 2.1-5.4 microgram/ml of blood were able to inhibit the maturation of P. falciparum parasites. Therefore, these studies indicate that Plasmodium falciparum are still sensitive to quinine and quinine remains to be the drug of choice for the treatment of falciparum malaria in Thailand.