Juan A. Jimenez

Optimization and Evaluation of a PCR Assay for Detecting Toxoplasmic Encephalitis in Patients with AIDS

ABSTRACT Toxoplasma gondii is a common life-threatening opportunistic infection. We used experimental murine T. gondii infection to optimize the PCR for diagnostic use, define its sensitivity, and characterize the time course and tissue distribution of experimental toxoplasmosis. PCR conditions were adjusted until the assay reliably detected quantities of DNA derived from less than a single parasite. Forty-two mice were inoculated intraperitoneally with T. gondii tachyzoites and sacrificed from 6 to 72 h later. Examination of tissues with PCR and histology revealed progression of infection from blood to lung, heart, liver, and brain, with PCR consistently detecting parasites earlier than microscopy and with no false-positive results. We then evaluated the diagnostic value of this PCR assay in human patients. We studied cerebrospinal fluid and serum samples from 12 patients with AIDS and confirmed toxoplasmic encephalitis (defined as positive mouse inoculation and/or all of the Centers for Disease Control clinical diagnostic criteria), 12 human immunodeficiency virus-infected patients with suspected cerebral toxoplasmosis who had neither CDC diagnostic criteria nor positive mouse inoculation, 26 human immunodeficiency virus-infected patients with other opportunistic infections and no signs of cerebral toxoplasmosis, and 18 immunocompetent patients with neurocysticercosis. Eleven of the 12 patients with confirmed toxoplasmosis had positive PCR results in either blood or cerebrospinal fluid samples (6 of 9 blood samples and 8 of 12 cerebrospinal fluid samples). All samples from control patients were negative. This study demonstrates the high sensitivity, specificity, and clinical utility of PCR in the diagnosis of toxoplasmic encephalitis in a resource-poor setting.

Multiplex PCR for Differential Identification of Broad Tapeworms (Cestoda: Diphyllobothrium) Infecting Humans

ABSTRACT The specific identification of broad tapeworms (genus Diphyllobothrium) infecting humans is very difficult to perform by morphological observation. Molecular analysis by PCR and sequencing represents the only reliable tool to date to identify these parasites to the species level. Due to the recent spread of human diphyllobothriosis in several countries, a correct diagnosis has become crucial to better understand the distribution and the life cycle of human-infecting species as well as to prevent the introduction of parasites to disease-free water systems. Nevertheless, PCR and sequencing, although highly precise, are too complicated, long, and expensive to be employed in medical laboratories for routine diagnostics. In the present study we optimized a cheap and rapid molecular test for the differential identification of the most common Diphyllobothrium species infecting humans (D. latum, D. dendriticum, D. nihonkaiense, and D. pacificum), based on a multiplex PCR with the cytochrome c oxidase subunit 1 gene of mitochondrial DNA.

DEVELOPMENT OF AN ENZYME-LINKED IMMUNOELECTROTRANSFER BLOT (EITB) ASSAY USING TWO BACULOVIRUS EXPRESSED RECOMBINANT ANTIGENS FOR DIAGNOSIS OF TAENIA SOLIUM TAENIASIS

Taeniasis diagnosis is an important step in the control and elimination of both cysticercosis and taeniasis. We report the development of 2 serological taeniasis diagnostic tests using recombinant antigens rES33 and rES38 expressed by baculovirus in insect cells in an EITB format. In laboratory testing with defined sera from nonendemic areas, rES33 has a sensitivity of 98% (n = 167) and a specificity of 99% (n = 310) (J index: 0.97); rES38 has a sensitivity of 99% (n = 146) and a specificity of 97% (n = 275) (J index: 0.96). Independent field testing in Peru showed 97% (n = 203) of the taeniasis sera were positive with rES33, and 100% of the nontaeniasis sera (n = 272) were negative with rES33; 98% (n = 198) of taeniasis sera were positive with rES38, and 91% (n = 274) of the nontaeniasis sera were negative with rES38. Among the Peruvian sera tested, 17 of 26 Peruvian Taenia saginata sera were false positive with rES38 test. Both tests were also examined with cysticercosis sera, with a positive rate ranging from 21% to 46%. rES33 and rES38 tests offer sensitive and specific diagnosis of taeniasis and easy sample collection through finger sticks that can be used in large-scale studies. They are currently being used in cysticercosis elimination programs in Peru.

Detection of Taenia solium Taeniasis Coproantigen Is an Early Indicator of Treatment Failure for Taeniasis

ABSTRACT Taenia solium causes taeniasis and cysticercosis, a zoonotic complex associated with a significant burden of epilepsy in most countries. Reliable diagnosis and efficacious treatment of taeniasis are needed for disease control. Currently, cure can be confirmed only after a period of at least 1 month, by negative stool microscopy. This study assessed the performance of detection by a coproantigen enzyme-linked immunosorbent assay (CoAg-ELISA) for the early evaluation of the efficacy of antiparasitic treatment of human T. solium taeniasis. We followed 69 tapeworm carriers who received niclosamide as standard treatment. Stool samples were collected on days 1, 3, 7, 15, 30, and 90 after treatment and were processed by microscopy and CoAg-ELISA. The efficacy of niclosamide was 77.9% (53/68). Thirteen patients received a second course of treatment and completed the follow-up. CoAg-ELISA was therefore evaluated for a total of 81 cases (68 treatments, 13 retreatments). In successful treatments (n = 64), the proportion of patients who became negative by CoAg-ELISA was 62.5% after 3 days, 89.1% after 7 days, 96.9% after 15 days, and 100% after 30 days. In treatment failures (n = 17), the CoAg-ELISA result was positive for 70.6% of patients after 3 days, 94.1% after 7 days, and 100% after 15 and 30 days. Only 2 of 17 samples in cases of treatment failure became positive by microscopy by day 30. The presence of one scolex, but not multiple scolices, in posttreatment stools was strongly associated with cure (odds ratio [OR], 52.5; P < 0.001). CoAg-ELISA is useful for the assessment of treatment failure in taeniasis. Early assessment at day 15 would detect treatment failure before patients become infective.

Differentiating Taenia eggs found in human stools: does Ziehl-Neelsen staining help?

Objective  To determine whether Ziehl‐Neelsen staining can differentiate Taenia solium from Taenia saginata eggs.

Diphyllobothrium pacificum Infection is Seldom Associated with Megaloblastic Anemia

Twenty cases of Dyphillobothrium pacificum (fish tapeworm) infections were prospectively studied to determine whether this tapeworm is associated with megaloblastic anemia, as commonly reported for D. latum infections. The most frequent symptoms were fatigue and mild abdominal pain, which were identified in approximately 66.6% of the 18 patients interviewed. Fourteen patients received treatment with niclosamide and all were cured. The other six patients spontaneously eliminated the tapeworms. One patient, who also had chronic diabetes and gastric atrophy, had low vitamin B12 levels and megaloblastic anemia. In all other patients, including three other patients with anemia, baseline vitamin B12 levels were in the reference range and did not significantly change when re-assessed three months later. Unlike D. latum, infection with D. pacificum is seldom associated with megaloblastic anemia or vitamin B12 deficit.

Evaluation of immunodiagnostics for toxocarosis in experimental porcine cysticercosis

We assessed whether immunodiagnostic tests for cysticercosis can cross‐react with the currently available immunodiagnostic tests for Toxocara canis in an established animal model for cysticercosis infection in pigs, known host for Toxocara. We examined by TES‐enzyme‐linked immunosorbent test and immunoblot assay for toxocarosis and cysticercosis the baseline and final follow‐up sera of 10 pigs, before and after (3 months) infection with Taenia solium. After successful cysticercosis infection, the nine evaluable pigs became seropositive to T. solium (enzyme‐linked immunoelectrotransfer blot assay), but did remain seronegative for Toxocara in both assays, documenting the lack of cross‐reactivity with anti‐T. solium antibodies in both T. canis assays. These findings should help clinicians better interpret serology for toxocariosis and cysticercosis in endemic areas for both helminth infections.