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Biomedical subjects

V Gathiram

Publications and source records attributed to V Gathiram.

34 records · Page 2Linked to original sources
PubMed1990

Pathogenic and nonpathogenic strains of Entamoeba histolytica can be differentiated by monoclonal antibodies to the galactose-specific adherence lectin.

Entamoeba histolytica infection results in either asymptomatic colonization or invasive colitis and liver abscess. E. histolytica isolates from patients with invasive disease have characteristic isoenzyme profiles (pathogenic zymodemes), suggesting a role for parasite factors in determining the severity of infection. A galactose-specific cell surface lectin from a pathogenic zymodeme was shown to mediate in vitro adherence to human colonic mucins and contact-dependent killing of target cells. Six nonoverlapping antigenic determinants were identified on the 170-kilodalton heavy subunit of the pathogenic lectin. Anti-lectin monoclonal antibodies (MAb) directed against epitopes 1 and 2 enhanced adherence whereas MAb to epitopes 3 through 6 either inhibited or had no effect on adherence. We tested 50 pathogenic and nonpathogenic strains for reactivity to these anti-lectin MAb by radioimmunoassay. MAb to epitopes 1 through 6 reacted in the radioimmunoassay with all 16 pathogenic zymodeme strains tested. In contrast, only MAb to epitopes 1 and 2 bound to the lectin from nonpathogenic strains. Western immunoblots with anti-lectin antibodies showed that the 170-kilodalton heavy subunit was present in the nonpathogenic amebae. Adherence of the nonpathogenic SAW 760 strain to human erythrocytes was enhanced by MAb to epitope 1 and blocked by galactose, confirming the presence of a functionally active lectin. A lectin radioimmunoassay based on MAb to epitopes 1 and 3 proved to be a simple and rapid method to distinguish pathogenic from nonpathogenic amebae in culture. Further exploration of the functional consequences of the antigenic differences demonstrated for the lectin may lead to a better understanding of its role in pathogenesis.

Animals↗
PubMed1990

Detection of Entamoeba histolytica immunoglobulins G and M to plasma membrane antigen by enzyme-linked immunosorbent assay.

Sixty-one serum specimens from 22 patients with clinically diagnosed amoebic liver abscess (ALA), 10 hospitalized patients with a variety of diseases other than amoebiasis, 12 normal healthy controls, and 17 subjects from an amoebiasis-endemic area were assayed by enzyme-linked immunosorbent assay (ELISA). The plasma membrane fraction of axenic cultures of Entamoeba histolytica HK9 separated from other subcellular fractions by differential centrifugation was used as the antigen to detect specific immunoglobulin G (IgG) and IgM antibodies. Using a single serum dilution of 1/100 and optical densities at 492 nm of 0.200 and 0.250 as the cutoff values for the IgM and IgG ELISAs, their respective sensitivities in 22 ALA patients were 91% (20 of 22) and 95% (21 of 22). In 22 patients (10 hospitalized and 12 normal healthy controls), the specificities of the IgM and IgG ELISAs were 95% (21 of 22) and 91% (20 of 22), respectively. All five asymptomatic carriers of pathogenic E. histolytica were seropositive by the IgG ELISA and the amoebic gel diffusion test (AGDT). The AGDT was positive for three of six culture-negative controls, while the IgG ELISA was positive for all six. For six asymptomatic carriers of nonpathogenic zymodemes, the AGDT was positive for two, and the IgG ELISA was positive for three. There was an excellent correlation (r = 0.96) between the IgG ELISA and the AGDT. Only one of six culture-negative controls, none of the asymptomatic carriers of pathogenic E. histolytica, and one of six carriers of nonpathogenic E. histolytica were seropositive by the IgM ELISA, thus highlighting the specificity of the IgM ELISA in the diagnosis of ALA. It is believed that the use of plasma membrane fractions has improved the diagnostic potential of the IgM ELISA.

Animals↗
PubMed1990

Entamoeba histolytica: naturally occurring infections in baboons.

Entamoeba chattoni frequently occurs as an intestinal infection in non-human primates. It has been isolated from both wild and captive animals. Morphologically this amoeba resembles E. histolytica. E. histolytica has also been isolated from non-human primates on a number of occasions but these isolations have been from captive animals. In recent years identification of E. histolytica has been enhanced by the introduction of iso-enzyme electrophoresis methods. This technology has been widely applied to amoebae isolated from humans from many parts of the world. Limited work using iso-enzyme electrophoresis on non-human primates in captivity has confirmed the earlier parasitological studies mentioned above as both E. histolytica and E. chattoni were isolated; furthermore zymodeme (strain or species based on the characteristic iso-enzyme electrophoretic pattern) analysis demonstrated that these two organisms could be readily distinguished by this method. The importance of establishing whether E. histolytica occurs in wild primates as a true zoonosis was emphasised by these studies, particularly from the point of view of potential disease transmission. A study of baboons (Papio ursinus) in South African game reserves has been initiated and three surveys have been conducted in the Kruger National Park; these baboons are considered to live in isolation from humans. Of the 210 isolations attempted 65-75% yielded E. chattoni while E. histolytica were cultured from the faeces of 1-3% of the baboons. Although the prevalence rates varied in each of the 3 study locations both species of amoeba were found in baboons from all of them. All the E. histolytica isolated thus far have been non-pathogenic zymodemes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Severe reversible myopathy due to typhoid.

An 18-year-old Black male presented to hospital with a fever and inability to walk due to severe proximal myopathy. He was found to have typhoid, and marked elevation of the creatine phosphokinase with myoglobinuria was recorded. After appropriate antibiotic therapy the creatine phosphokinase level returned to normal and the patient made a complete recovery. Although neuropsychiatric manifestations have been commonly recorded in typhoid, the complication of a myopathy has not been frequently noted.

Adolescent↗
PubMed1988

Evaluation of an enzyme-linked immunosorbent assay in the serodiagnosis of amoebic liver abscess.

An indirect enzyme-linked immunosorbent assay (ELISA) was evaluated for the detection of anti-amoebic IgG and IgM antibodies to assess its value in distinguishing past from current infection in invasive amoebiasis, particularly in amoebic liver abscess (ALA) patients. Using sera from 295 individuals, the ELISA was also compared with the amoebic gel diffusion (AGD) test. In 100 patients the IgG-ELISA at a single test dilution of 1/6,400 had a sensitivity of 99% for clinically diagnosed ALA. In these same patients the IgM-ELISA at a single dilution of 1/400, had a sensitivity of 64% and a specificity of 97.9%. No cross-reactions were observed in sera from patients with collagen vascular disease. In 121 patients without clinical invasive amoebiasis, 8 were AGD-positive and 12 were IgG-ELISA-positive, giving the latter assay a specificity of 91.7%. This is thought to be due to past infection with Entamoeba histolytica. In symptomless carriers of pathogenic zymodemes, 10/11 were seropositive by the IgG-ELISA and 11/11 by the AGD test. There was an excellent correlation between the IgG-ELISA and the AGD test (r = 0.99). The IgG-ELISA is a sensitive, specific, simple and rapid test. It has the clinical advantage that results are obtainable 2 1/2 hours after receipt of the specimen, compared with the 24-48 hours required for the AGD test. The prompt availability of IgG-ELISA results could prove advantageous for implementation of early therapy. The IgM-ELISA was not found to be sensitive enough to be used as an index of active amoebic infection.

Enzyme-Linked Immunosorbent Assay↗
PubMed1987

A longitudinal study of asymptomatic carriers of pathogenic zymodemes of Entamoeba histolytica.

The value of treating subjects who pass Entamoeba histolytica cysts in their faeces is currently in question. In the endemic Durban area iso-enzyme electrophoresis of E. histolytica isolates indicated that 1% of the asymptomatic population are infected with pathogenic zymodemes. The outcome of these potentially invasive infections was established by means of a longitudinal survey. All subjects had strongly positive serological responses--10% of them developed amoebic colitis while the rest remained asymptomatic and spontaneous cure occurred within 1 year. Infections with pathogenic zymodemes occurred in family units and closely related individuals. Since they were cyst passers, good evidence was obtained for the existence of a carrier state for pathogenic E. histolytica. The value of sero-epidemiological surveys in determining the prevalence of pathogenic E. histolytica in a community was highlighted. Treatment of asymptomatic carriers with pathogenic zymodemes of E. histolytica is as essential as treatment of patients with invasive amoebiasis, and in both cases all contacts of affected individuals must also be treated if they are found to harbour pathogenic zymodemes of E. histolytica in order to ensure control of disease transmission.

Adolescent↗
PubMed1986

Specificity of the Testryp CATT card agglutination test in a non-sleeping-sickness area of Africa.

A card agglutination test (CATT), recently developed for the diagnosis of trypanosomiasis, has been evaluated in certain southern African localities; 179 blood specimens and 63 serum samples from black patients of both sexes and widely ranging ages, suffering from a variety of generalized and parasitic disorders, were tested. False-positives were minimal (2.9%) and there were no cross-reactions with any of the parasitic infections. The CATT is therefore regarded as a highly specific and sensitive test, which can be performed effectively in the field by non-specialist personnel.

Adolescent↗
PubMed1985

A comparative trial of metronidazole v. tinidazole in the treatment of amoebic liver abscess.

Forty-eight patients were treated for amoebic liver abscess, 27 with metronidazole (Flagyl; Maybaker) and 21 with tinidazole (Fasigyn; Pfizer). Although 4 patients treated with tinidazole and 2 treated with metronidazole required a second course of therapy, both drugs were highly effective and resulted in rapid clinical improvement. The only side-effect was oral candidiasis, which developed in 2 patients in each drug group.

Adult↗
PubMed1985

Seroepidemiological study of antibody responses to the zymodemes of Entamoeba histolytica.

In 303 apparently healthy subjects and 54 patients with confirmed invasive amoebiasis amoebae were isolated where possible, and Entamoeba histolytica was classified into its various zymodems. 20% of the healthy subjects were antibody-positive; 17 healthy subjects proved to be symptomless carriers of pathogenic zymodemes and, like patients with invasive disease, all these were seropositive. Furthermore, of subjects infected with pathogenic zymodemes 94-100% were strongly seropositive, compared with 2-4% of subjects with non-pathogenic zymodemes. Pathogenic zymodemes are therefore believed to be in constant contact with the host's tissues, even in symptom-free individuals; the presence of these potentially invasive organisms is thought to be directly related to the seropositivity in a given population, and seroepidemiological surveys would therefore provide information only on the distribution of this form of the parasite. Quantitative serological data constitute valuable information on the endemicity of an area, and the results will gain reliability from use of two complementary tests instead of one.

Antibody Formation↗
PubMed1985

Frequency distribution of Entamoeba histolytica zymodemes in a rural South African population.

To determine the prevalence of Entamoeba histolytica and its zymodeme distribution pattern, isoenzyme electrophoresis was performed on isolates of the parasite from 1381 individuals of the population of a semirural endemic area south of Durban. About 10% of the population was found to harbour E histolytica. The zymodeme distribution was similar to that described in other surveys but two new zymodemes were observed, a non-pathogenic zymodeme XIX and a pathogenic zymodeme XX. Non-pathogenic zymodemes were more frequent in females than in males. In apparently healthy individuals there was a 1% prevalence of pathogenic E histolytica; the distribution was the same in males and females even though invasive amoebiasis was far more common in males. Symptoms of amoebic colitis subsequently developed in only 2 of the 14 symptomless individuals from whom pathogenic zymodemes of E histolytica were isolated.

Adolescent↗
PubMed1985

Cell-mediated immunity in hepatic amoebiasis.

Cell-mediated immunity (CMI) was measured by blastic transformation of peripheral blood lymphocytes in 26 patients with amoebic liver abscess (ALA) and matched control subjects with no demonstrable clinical amoebiasis. During active disease, the mean mitogenic response, measured by the stimulation index of the patients' lymphocytes to Entamoeba histolytica antigen, was increased (mean +/- SD: 25.98 +/- 46.62 compared with 11.27 +/- 21.39), whereas that to phytohaemagglutinin (PHA) was reduced (54.80 +/- 56.26 compared with 111.70 +/- 70.61). Both these results were statistically significant (P less than 0.01); they do not, however, appear to be due to a quantitative defect in T-cell numbers, as both total peripheral lymphocytes (3332 +/- 1450 cells/microliters compared with 2447 +/- 531 cells/microliters) and T-cells (2652 +/- 1128 cells/microliters compared with 1908 +/- 386 cells/microliters) were significantly elevated in the patients (P less than 0.01). When these tests were repeated two months later in 12 cured patients they were found to be comparable to those of the control subjects. The results indicate that there is a transient cellular sensitization to amoebic antigen together with an increase in T-lymphocytes and an impairment of the mitogenic response of lymphocytes to PHA. The significance of these findings is discussed.

Adolescent↗
PubMed1985

Serial ultrasound in amoebic liver abscess.

Serial ultrasound examinations were conducted in 93 patients with amoebic liver abscess. The initial size of the abscesses ranged from 3 to 17 cm. The time taken for complete healing to occur varied from 10 to 300 days and correlated directly with the initial size of the abscess cavity. As healing progressed, the abscess cavity became increasingly hypoechoic and assumed a smoother margin. In uncomplicated cases, complete healing occurred and, on ultrasound, no residual lesions were seen in the liver. There were two cases each of delayed healing and recurrence of amoebic liver abscess and the value of ultrasound in these situations is discussed. Ultrasound examination of the liver appears to be very suitable for assessing satisfactory progress of healing in amoebic liver abscess.

Humans↗
PubMed1984

Concomitant and secondary bacterial infection of the pus in hepatic amoebiasis.

In a series of 48 consecutive patients with clinically diagnosed uncomplicated amoebic liver abscess (ALA), the pus obtained by closed drainage of the abscess was bacteriologically sterile. Secondary bacterial infection of the ALA as a direct result of the aspiration procedure occurred in only 1 patient, the causative organism being Escherichia coli. Entamoeba histolytica was identified in a total of 39 cases (81%) by means of direct microscopy of the pus as well as culture methods.

Amebiasis↗
PubMed1984

The iron status of Black subjects with amoebiasis.

Hepatic iron concentrations were measured in 60 Black patients who had died of amoebiasis. There were 18 infants and young children, 30 adult males and 12 adult females. The mean hepatic iron concentration in infants was normal (0,11% dry weight), while those in adult males and females were significantly raised (0,64% and 0,30% dry weight respectively). The figures for adults are somewhat higher than those previously found in Black subjects, suggesting that iron overload is more common in patients with amoebiasis than in the general population. The relevance of these findings to the pathogenesis of amoebiasis is not clear but the relationship may well not be a direct one, since hepatic iron stores were no larger in patients with liver abscesses than in subjects without.

Adult↗