Positive Complement Fixation Test Research Articles

Isolation, serological and molecular methods in screening of Burkholderia mallei in East Azerbaijan province, Iran.

Glanders caused by Burkholderia mallei is one of the most dangerous zoonotic diseases in solipeds. Clinical diagnosis of this disease in its early stages in horses, is difficult. This study investigated serological and molecular identification of B. mallei in East Azerbaijan province. In the third and fourth quarters of 2020, throughout 2021, and in the first and second quarters of 2022, the complement fixation test (CFT) was performed on 350 horses. The malleination was used to confirm the positive CFT cases. Blood samples were taken for culture and for preparing serums to perform the enzyme-linked immunosorbent assay (ELISA). Deep eye discharge, nostril, cutaneous ulcers and lymph fluid swabs were cultured, and polymerase chain reaction (PCR) was carried out. Eleven horses were CFT-positive. Based on the malleination on the 11 horses, six were affected by glanders, five were not affected (false positive), and one horse was CFT-negative despite exhibiting clinical signs. It was positive by malleination, ELISA and PCR. A total number of seven positive cases of glanders were diagnosed. The B. mallei could not be isolated, but the Burkholderia cepacia complex was isolated in one case. Except for three cases, the results of the CFT, mallein and ELISA tests were consistent. The amount of confidence interval was 95.00%. It is suggested that ELISA could be used as a complement to CFT in screening and, if positive results are observed in one of the tests, the entire herd must be examined more accurately using the mallein and western blot confirmatory tests.

Risk Factor Identification and Incidence Rate Measurement on One High-Risk Farm as Brucellosis Precautions in Metro City Lampung

Since 2011, Lampung is one of the Brucella-free areas, but April 2021 reported abortion case in a cow farm at Metro city Lampung Province. The purpose of this study was to identify risk factors and measure incidence levels as vigilance re-emerging Brucellosis. Sample of cow serum, taken in a census from whole cattle cow in a farm at risk, as much as 2 times with a distance about 1 month. In the first census, 703 serum samples were taken from the stables and 25 samples from the adjacent. Whole sample tested to Brucella spp with rose bengal test (RBT) and positive result confirmed with complement fixation test (CFT). The second census was conducted on samples without positive CFT results in the first census. The positive RBT at second sensus were followed by CFT and c-Elisa tests. Incidence rate of brucellosis in high-risk housing in Banjarsari Village, North Metro District, Metro City 1,67% or 2 brucellosis per 100 cows a month. Brucella spp. seropositivity was significantly related to the type of species and sex of the animal; animals with Ongole breed 4.2 times and female animals 4.5 times have a higher level of exposure compared to non-Ongole breed animals and males.

Development of a microsphere‐based immunoassay for the serological detection of glanders in equids

Burkholderia mallei is the etiologic agent of glanders, an infectious disease of solipeds, with renewed scientific interest due to its increasing incidence in different parts of the world. More rapid, sensitive and specific assays are required by laboratories for confirmatory testing of this disease. A microsphere‐based immunoassay consisting of beads coated with B. mallei recombinant proteins (BimA, GroEL, Hcp1, and TssB) has been developed for the serological diagnosis of glanders. The proteins’ performance was compared with the OIE reference complement fixation test (CFT) and an indirect enzyme‐linked immunosorbent assay (iELISA) on a large panel of sera comprised of uninfected horses (n=198) and clinically confirmed cases of glanders from India and Pakistan (n=99). Using Receiver Operating Characteristics (ROC) analysis and adjusting the cutoff levels, Hcp1 (Se=100%, Sp=99.5%) and GroEL (Se= 97%, Sp=99.5%) antigens exhibited the best specificity and sensitivity. Neither Hcp1 and GroEL proteins, nor iELISA reacted with doubtful and positive CFT samples from glanders free countries which further confirmed the false positive reactions seen in CFT.

Brucella melitensis B115-based ELISA to unravel false positive serologic reactions in bovine brucellosis: a field study

BackgroundBrucellosis is a zoonosis whose incidence is not declining worldwide despite the global effort to control the disease. Accurate and precise diagnosis is a crucial step in any prophylaxis program but single tests to unequivocally detect animals infected with Brucella spp. are currently unavailable. In Italy, serological diagnosis of bovine brucellosis is performed with two official tests: a rapid agglutination test (i.e., Rose Bengal Plate test, RBPT) and a complement fixation test (CFT) that detect antibodies directed mainly to the smooth lipopolysaccharide (S-LPS). Neither of the two tests is able to avoid the detection of false positive serological reactions (FPSRs) caused by bacteria sharing S-LPS components with Brucella spp. and responsible for the single reactors (SR) phenomenon. A B. melitensis R strain-based ELISA showed a good diagnostic performance in unravelling FP animals; however, since a limited number of animals were analyzed in that study, a large field study was conducted here to discriminate between Brucella-infected from FP animals, with the final aim of reducing the unnecessary slaughter of the latter. An ELISA based on a R strain of Brucella, i.e., Brucella melitensis B115, was employed to measure specific IgG responses in a collection of bovine sera (n = 648). Sera were obtained from 180 farms (either officially brucellosis-free or not brucellosis-free) recruited during an extended period of time (2014–2018) and were preliminarily assayed with the official tests by the Italian Reference Centers and then subjected to the ELISA.ResultsNegative sera, when subjected to the ELISA, gave O.D. values below the cutoff; SR sera, i.e. RBPT positive and CFT negative, as well as double positive (DP) sera, i.e. RBPT and CFT positive, gave O.D. values that were below the cutoff. All positive sera, i.e. from Brucella-infected animals, were RBPT positive and CFT positive (ICFTU ranging from 20 to 1280) and gave ELISA O.D. values above the cutoff.ConclusionsThe B. melitensis B115-based ELISA systematically unravelled all false positive (FP) sera while confirming the diagnosis in Brucella-infected animals. Thus, the test employed in the present study may complement the official assays to avoid the costly slaughter of FP animals.

Risk factors associated with clinical signs of vesicular stomatitis and seroconversion without clinical disease in Colorado horses during the 2014 outbreak

Vesicular stomatitis (VS) is caused by a contagious rhabdovirus that affects horses, cattle, and swine. Clinical signs of vesicular stomatitis virus (VSV) infection in pigs and cattle are indistinguishable from foot-and-mouth disease (FMD), a foreign animal disease and reportable disease in the United States (Rodriguez et al., 2000). A VS epidemic occurred in the Rocky Mountain region in 2014–15. A study was conducted in Colorado to evaluate horse- and management-level factors associated with VS. For a horse to be considered a clinical VS horse, there were two requirements. First, clinical VS horses had to have clinical signs consistent with VS, including one or more of the following: vesicles, ulcers, erosions or crusting on the muzzle, nares, lips, oral or nasal mucosa, ears, ventrum, udder or penile sheath, or coronary band lesions. Second, clinical VS horses had to have laboratory confirmation of VSV exposure via virus isolation from lesions or a positive complement fixation test performed on sera. All non-clinical horses residing on VSV-affected premises enrolled in the study were evaluated for exposure (i.e., seroconversion) to VSV. Overall, management and housing data were collected from 334 horses on 48 premises in Colorado. Approximately one-third (31.4%) of enrolled horses were clinical cases and two-thirds (68.6%) were controls. Three premises-matched logistic regression models were constructed in SAS using backward elimination (P-value < 0.05) after univariate screening of a priori-selected variables (P-value < 0.20). Model outcomes included differences in characteristics and management of 1) clinical and nonclinical horses, 2) exposed and unexposed horses, and 3) exposed nonclinical and unexposed nonclinical horses. Overall, factors most strongly associated with risk of being a VS clinical horse were access to pasture (P-value = 0.002), and pregnancy status (P-value = 0.001). Factors most strongly associated with VSV exposure among horses were access to pasture (P-value = 0.003) and lack of any insect control (P-value = 0.001). The only factor associated with VSV-exposed nonclinical horses compared with unexposed VSV horses was contact with clinical horses (P-value = 0.013). There were no associations identified regarding clinical horses compared with exposed nonclinical horses. With regard to severity of lesions (severe vs. moderate or mild), no variables met the criteria for inclusion in the multivariable model. Results of this study provide evidence that pasture access and fly control are important factors associated with VSV exposure.

Cavitation and Confusion: A Puzzling Presentation of Granulomatous Disease

SESSION TITLE: Student/Resident Case Report Poster - Pulmonary Manifestations of Systemic Disease II SESSION TYPE: Student/Resident Case Report Poster PRESENTED ON: Tuesday, October 25, 2016 at 01:30 PM - 02:30 PM INTRODUCTION: A 32-year-old HIV-negative African American man presented with a 7-month history of altered mental status (AMS) and functional decline for which he underwent multiple rounds of hospitalizations and diagnostic testing before the correct diagnosis was made. CASE PRESENTATION: He was first seen at an outlying hospital for AMS, which was attributed to drug use. Chest x-ray (CXR) revealed bilateral cavitary lung lesions, and he was treated for pneumonia and discharged. He returned one month later with persistent AMS. Brain MRI showed diffuse leptomeningeal enhancement. Lumbar puncture (LP) revealed lymphocytic pleocytosis, low glucose, and elevated protein. All infectious testing was negative. Transbronchial lung biopsy showed inflammation, but no organisms. He was discharged on itraconazole for presumed disseminated fungal infection. He returned with progressive mental status changes four months later. MRI and LP were unchanged, but CSF angiotensin-converting enzyme (ACE) was four times normal. Chest imaging again showed cavitary lesions, and CT guided lung biopsy revealed necrotizing granulomatous inflammation. Microbiological tests were again negative except one serum complement fixation (CF), which was positive for histoplasmosis. The patient was treated with amphotericin and discharged on itraconazole until he presented to us two months later. By this time, the patient had developed gait abnormalities and urinary incontinence. Imaging demonstrated progression of prior lesions. Both transbronchial lung and brain biopsies revealed necrotizing and non-necrotizing granulomas. All fungal tests including histoplasmosis fungal CF were negative. Serum ACE level was elevated and, considering prior elevated CSF ACE and granulomas in the lung and brain, sarcoidosis was diagnosed. The patient was treated with high dose steroids and his clinical status, along with lung and brain lesions, improved. DISCUSSION: The elusiveness of this diagnosis in large part stemmed from the common diagnostic pitfalls of anchoring bias and reliance on general disease paradigm rather than specific clinical context. Despite the severity and progression of the patient’s symptoms on treatment, an incorrect diagnosis persisted on the basis of a single positive complement fixation test without microbiological confirmation. Additionally, the elevated CSF ACE was ignored in this unusual presentation of sarcoidosis. Although sarcoid is classically thought of as non-necrotizing, recent literature suggests sarcoidosis can cause a spectrum of granulomatous inflammatory tissue responses. CONCLUSIONS: This case illustrates the importance of ongoing diagnostic re-evaluation with consideration of atypical presentations of rare diseases when faced with discordant laboratory data or unexpected clinical progression. Reference #1: Rosen Y. Four decades of necrotizing sarcoid granulomatosis: what do we know now? Arch Pathol Lab Med. 2015;139(2):252-62. DISCLOSURE: The following authors have nothing to disclose: Meredith Greer, Udayan Shah No Product/Research Disclosure Information

Seroconversion and semen shedding in rams experimentally infected with Brucella ovis

AIM: To determine the time taken for rams to develop antibodies to Brucella ovis in serum, shed B. ovis in semen and develop lesions of epididymitis following infection with B. ovis.METHODS: Fifteen 19-month-old rams were artificially infected with B. ovis by inoculation of infected semen onto the nasal and rectal mucus membranes (Day 0). Serum was collected from each ram at 2 to 8-day intervals and tested at commercial laboratories using a complement fixation test (CFT) and an ELISA. Cut-off values for the CFT were 0–4/4 negative; 1/8–3/8 suspicious and 4/8–4/128 positive, and for the ELISA were <10% negative; ≥10 to <50% suspicious and ≥50% positive. Selected serum samples were also tested using a gel diffusion test (GDT). At 7 to 8-day intervals semen was collected for bacterial culture and the scrotal contents were palpated to identify lesions of epididymitis. The study was terminated after 56 days.RESULTS: On Day 28 B. ovis was isolated from the semen of one ram and by Day 49 it was isolated from the semen of 10 rams. All 10 rams had suspicious or positive ELISA or CFT titres by Day 36 and 56, respectively. The GDT results were all negative on Day 36 and in general did not become positive in individual rams until 7–28 days after semen shedding commenced. Epididymitis was detected in one ram on Day 36; by Day 56 eight rams had epididymitis detectable by scrotal palpation.CONCLUSIONS: The B. ovis ELISA test identified infected rams at an earlier stage than the CFT; this was at 19–36 days after exposure. Rams can begin shedding B. ovis in semen as early as 28 days after exposure and lesions of epididymitis develop as early as 36 days after exposure.CLINICAL RELEVANCE: During a test and slaughter campaign for the control of B. ovis, the most appropriate serological re-testing interval is likely to be around 28 days (4 weeks) using the ELISA with or without the CFT, although caution is required in interpretation of “suspicious” ELISA results. Following a B. ovis breakdown, two negative CFT or ELISA tests 60 days apart are recommended to confirm freedom from infection, supporting current guidelines.

Serological diagnosis of Mycoplasma pneumoniae infection: a complicated puzzle

Background. Mycoplasma pneumoniae has a prominent role in respiratory tract infections, especially in children and young adults. Serological methods, in particular complement fixation test (CFT) and enzyme immunoassays (ELISA), are most widely used for the diagnosis. However, a reliable diagnosis remains difficult to achieve. Study Design. The population study was subdivided in 2 groups. Group 1) 52 serum samples from blood donors; group 2) 50 serum samples from 50 patients (23 women, 27 men) affected by atypical pneumonia. The mean age was 29.2 years (1 to 85 years) and 48% was under 20 years.The following commercial products were used: Chorus M. pneumoniae ELISA IgG and IgM, Chorus CFT total Ig (DIESSE, Siena, Italy). Results. Group 1) 67.3% of blood donors resulted positive for IgG and 19.2% positive or equivocal for IgM. Group 2) specific IgG were detected in 70% of the patients and IgM resulted positive or equivocal in 64%. Since the number of IgG positive subjects was similar in the 2 groups, the CFT test was added to better define acute stage of infection.The CFT test resulted positive in 92.3% of the IgG+IgM+, and in 41.7% of the IgG+IgM- serum samples, respectively. Conclusions. High titers of IgG do not necessarily identify acute or recent infection, as previously suggested. The CFT test showed a good correlation with ELISA test in IgG+IgM+ serum samples. Detection of IgM antibodies is still the most reliable test to define acute infection, especially if confirmed by a positive CFT test.

Occult Varicella

Localized varicella has been associated with UV-exposure and skin trauma. Varicella restricted to a pre-existent dermatitis is exceptional. The clinical features, cytohistologic and immunohistochemical results, as well as serologic data of 6 patients with a sudden eruption of vesicular and eroded lesions restricted to a pre-existent dermatitis are presented. All patients (mean age: 8,3 years, range: 3-22) showed crops of a few to numerous vesicular lesions clustered on the restricted sites of posttraumatic wound, perianal streptococcal dermatitis, dermatomycosis, allergic contact dermatitis, lichen sclerosus, and atopic foot dermatitis. All the Tzanck smears and 1 biopsy revealed multinucleated giant cells, consistent with herpes simplex virus (HSV) or varicella zoster virus (VZV) infection. Immunohistochemistry using specific anti-VZV antibodies (IE63 and gE) was positive on all the smears and the biopsy, whereas HSV-I and HSV-II immunolabeling was negative. VZV specific IgM+, IgG- EIA-based serology, and positive VZV-specific IgM complement fixation test suggested primary VZV infection. None had received varicella vaccine. None of the patients presented a history of varicella nor experienced breakthrough varicella. It was decided not to administer antiviral treatment, as the varicella lesions remained localized without any further skin extension and systemic signs. About 2 months later, EIA-serology revealed positive VZV-IgG and negative IgM levels in 5/5 patients. Some patients have varicella infection that remains hidden in a pre-existent infectious and/or inflammatory dermatitis without ever presenting full-blown chickenpox. The sudden occurrence of vesicular and/or ulcerated lesions on a pre-existent dermatitis should prompt searching for a viral infection.

Complement Deposition Is Predictive of a Low Absolute Immature Platelet Fraction in Immune Thrombocytopenic Purpura

The role of platelet-associated complement in the pathophysiology of immune thrombocytopenic purpura (ITP) is not well understood. Although various humoral and cell mediated mechanisms have accounted for the decrease in platelet count, the role of the complement system has not been well defined. To test this, we examined complement fixation on platelets using plasma of 100 ITP patients and 50 healthy volunteers. In situ complement fixation was measured as C1q deposition on heterologous platelets using an ELISA approach. Deposition of C1q was evaluated using specific primary monoclonal antibodies (Quidel, San Diego, CA), and an alkaline phosphatase conjugated goat anti mouse secondary antibody and p-NPP substrate to quantify primary antibody binding. Substrate conversion was measured at 405 nm and was proportional to antigen deposition (complement component) on the platelet surface. Controls for specificity included wells coated with blocking solution only, and platelets exposed to buffer instead of plasma. Results for patient samples were normalized relative to an internal assay control (pooled normal plasma) and expressed as a ratio of C1q deposition. Ratios equal to or greater than 1.9 were considered positive for complement fixation. No significant relationship was observed for complement fixation when samples were stratified by gender, splenectomy status, prior treatment or total platelet count. However, a significant relationship between Absolute Immature Platelet Fraction (A-IPF) (Sysmex, Kobe, Japan) and C1q deposition was observed. The data suggest that a positive complement fixation test defined by C1q deposition is predictive of a low A-IPF (<15) with a positive predictive value and specificity of 100%. The two tailed Fisher exact test gives a p-value of 0.0265. In conclusion, these data suggest that complement fixation in the classical pathway may play a role in reducing the number of immature platelets in patients with ITP, perhaps by a direct effect of complement deposition on megakaryocytes and therefore anti-complement therapy may have clinical utility. Further studies that include an examination of complement fixation in the bone marrow, especially on megakaryocytes, may elucidate the exact mechanism of this destruction. Alernatively, flow cytomety of immature platelets to compare them to mature platelets in regard to complement deposition would be of interest.

Salmonella enterica Serotype Urbana Interference with Brucellosis Serology

Sheep were immunized with killed Salmonella enterica serotype Urbana cells and their sera were tested in various serological tests for antibody to Brucella sp., Yersinia enterocolitica O:9 and Escherichia coli O:157 H:7. Of the eight sheep, all gave a positive agglutination reaction in the brucellosis buffered antigen plate agglutination test (BPAT), seven gave positive brucellosis standard tube agglutination test (TAT) and complement fixation test (CFT) results and four gave slightly positive reactions in a competitive enzyme immunoassay (CELISA). Seven sera were negative in an indirect enzyme immunoassay (IELISA‐SLPS) using B. abortus smooth lipopolysaccharide (SLPS) antigen and all were negative in a fluorescence polarization assay (FPA‐OPS) using B. abortus O‐polysaccharide antigen. Two sheep gave a slight positive reaction in an IELISA using Brucella rough lipopolysaccharide antigen (IELISA‐RLPS) and four sheep were slightly positive in an FPA using Brucella LPS core antigen (FPA‐CORE). All sheep had high antibody responses to S. enterica serotype Urbana, Y. and E. coli O:157 and 7 were positive for antibody to Y. enterocolitica O:9 when tested by IELISA. The sheep were negative when tested in the FPA using OPS from Y. enterocolitica O:9 but all were strongly positive in the FPA using OPS from E. coli O:157 while seven sheep had titers to S. enterica serotype Urbana. The impact on diagnostic serology for brucellosis is discussed.

Characterization of Minaçu virus (Reoviridae: Orbivirus) and pathological changes in experimentally infected newborn mice

Minaçu virus was isolated from Ochlerotatus scapularis (Diptera: Culicidae) in Minaçu, Goiás State, Brazil, in 1996. In attempting characterization of virus serological (hemagluttination inhibition, HI; indirect immunofluorescence assay, IFA), physicochemical [test for deoxycholate acid (DCA) sensitivity; polyacrylamide gel electrophoresis (PAGE)] tests and ultrastructural studies were made. Virus was also assayed in suckling mice after intracerebral inoculation of 0.02 ml and in VERO and C6/36 cells with 0.1 ml of viral suspension containing 10(5) LD50/ml. Inoculated and control systems were observed daily. Every 24 h, one control and two inoculated animals were killed for tissue testing, including histopathological changes by haematoxylin and eosin (HE)-stained sections, which were semi-quantified. Research into viral antigen in the tissues of mice [central nervous system (CNS), liver, heart, lungs, spleen and kidneys] was carried out by the immunohistochemical technique using the peroxidase system. The virus only replicated in VERO cells, with antigen positive by IFA. Positive complement fixation tests were only obtained using antiserum of Minaçu virus. Minaçu virus is DCA resistant; haemagglutinating activity was negative. By electronic microscopy non-enveloped virus particles were 75 nm in diameter. PAGE analysis showed Minaçu virus genome profile with 10 RNA segments. Infected, non-killed animals died 7 days after inoculation. Tissue lesions were observed in all organs, except the lungs. Intense lesions were observed in the CNS and the heart, where neurone and cardiocyte necroses, respectively, were noted. The liver, spleen and kidneys had moderate tissue changes. Viral antigens were more abundant in the CNS and the heart, and absent in the lungs. In conclusion, Minaçu virus belongs to the family Reoviridae, genus Orbivirus.

Predictors of unfavourable prognosis in chronic Chagas' disease.

The aim of this study was to detect clinical predictors of left ventricular dysfunction, left ventricular dilatation and apical aneurysm on echocardiography, all known as independent predictors of lethal outcome for patients with chronic Chagas' disease. Seventy-four patients with a positive complement-fixation test for Chagas' disease participated; 44 (59%) had left ventricular dysfunction, 41 (55%) left ventricular dilatation and 15 (20%) apical aneurysm. A stepwise logistic regression analysis showed that systolic blood pressure (P < 0.001) and male sex (P < 0.001) were independent predictors of left ventricular dilatation on echocardiography. A receiver-operating characteristic curve provided a systolic blood pressure of 120 mmHg with a sensitivity of 70% and a specificity of 63% to predict left ventricular dilatation. The combination of male sex and systolic blood pressure of 120 mmHg had a sensitivity of 56% and a specificity of 91% to predict left ventricular dilatation. In a separate stepwise logistic regression analysis, left ventricular systolic dysfunction was independently predicted by systolic blood pressure (P = 0.006) and New York Heart Association functional class (P = 0.01). Receiver-operating curves provided a blood pressure of 120 mmHg with a sensitivity of 72% and a specificity of 59% to predict left ventricular dysfunction, whereas a New York Heart Association functional score of 2 predicted left ventricular systolic dysfunction with a sensitivity of 78% and a specificity of 50%. The combination of New York Heart Association functional class and a systolic blood pressure of 120 mmHg predicted left ventricular dysfunction with a sensitivity of 59% and a specificity of 77%. The apical aneurysm was independently predicted by myocardial necrosis on the resting ECG, but only with a sensitivity of 20%. Hence, echocardiographic markers of cardiac mortality and sudden cardiac death in Chagas' disease can be independently predicted by clinical examination. This may be useful for screening high-risk chagasic patients.

Evaluation of Anaplasma marginale from tick cell culture as an immunogen for cattle.

Anaplasma marginale has been propagated and continuously passaged in an Ixodes scapularis cell line. Anaplasma development was characterized and cultures with a high density of rickettsiae were harvested at a predictable rate. Culture-derived A. marginale (CAM) remained infective for cattle and was used effectively as antigen in diagnostic tests with the sensitivity to identify bovine carriers of A. marginale. This study presents results of an initial trial using the CAM as an immunogen for cattle. CAM was mechanically disrupted, frozen at -70 degrees C, and inactivated with beta-propiolactone. Two intact yearling cattle were immunized with CAM and Freund's adjuvant, receiving 4 subcutaneous injections at 3-4 week intervals. Two control yearling cattle received adjuvant and PBS. Serum samples were evaluated by competitive ELISA (C-ELISA) using CAM as antigen and the standard complement fixation test (CFT). All cattle were subsequently challenged with A. marginale-infected blood from a carrier cow. An additional intact calf was inoculated with live CAM from the same passage and screened by C-ELISA and CFT. Sera collected from immunized cattle were negative or suspicious by CFT throughout the immunization study. The same sera were strongly positive by C-ELISA two weeks after the first injection and throughout the study. All cattle became infected following challenge-exposure with blood, but immunized cattle exhibited longer prepatent periods as well as lower parasitemias and percent reduction of packed cell volumes as compared with the controls. The calf receiving live CAM became infected and underwent a mild clinical reaction with positive C-ELISA and CFT results and did not become clinically ill following blood challenge. This preliminary study suggests that the CAM antigen is highly immunogenic in cattle. Furthermore, the CFT did not identify immunized animals whereas the C-ELISA (using CAM) was highly sensitive for detection of both immunized and infected animals.

Results of electrophysiologic studies in patients with acute Chagasic myocarditis.

As the acute stage of Chagas' myocarditis is rarely detected, little is known about the electrophysiologic characteristics of that stage. This investigation was undertaken to conduct an electrophysiologic study of the properties of the heart during the acute phase of Chagasic myocarditis. We studied eight patients who had positive xenodiagnosis, positive mice culture, and positive complement fixation test for Chagas' disease. Trypanosoma cruzi were identified in all of the patients' stained blood samples. Right ventricular endomyocardial biopsies were obtained, evidencing a distinct infiltrate of lymphocytes that confirmed the diagnosis of acute myocarditis. The cardiac dimensions and the ventricular systolic and diastolic function were preserved in all patients. The electrocardiogram evidenced conduction defects in two patients. The signal-averaged electrocardiogram displayed late potentials in three patients. In the electrophysiologic study, atrial fibrillation or flutter was induced in four patients. When compared with control patients, Chagasic patients were found to have greater values of atrial threshold, A-H interval, and atrioventricular (AV) nodal effective refractory period. The H-V interval was mildly prolonged in two patients, but the dynamic AV nodal conduction was preserved (1:1 conduction during right atrial stimulation at a cycle length of 400 ms) in all the Chagasic patients. The ventricular parameters were within normal limits, and no sustained ventricular arrhythmia could be induced. Patients with mild acute Chagasic myocarditis may suffer from electrical abnormalities and arrhythmias that are more evident at the supraventricular level and the AV junction.

Intestinal Chlamydia in finishing pigs.

Gut and blood samples from 119 finishing pigs derived from 11 farms were collected during routine slaughter at an abattoir. Sections of formalin-fixed, paraffin-embedded tissues were labeled immunohistochemically using genus-specific, mouse monoclonal antibody against chlamydial lipopolysaccharide; goat polyclonal antiserum against the major outer membrane protein of Chlamydia trachomatis; and mouse monoclonal antibody against the ovine abortion subtype of C. psittaci. Gut samples from 33 of 111 (29.7%) individual pigs stained positive with the genus-specific monoclonal antibody, and of these 30 of 32 (93.7%) also reacted with the C. trachomatis-specific antiserum. Labeled inclusions were restricted to mature enterocytes of the large intestine in 33 of 111 cases. Infection of small intestinal enterocytes was noted in only one of 82 ileal samples. The blood samples were tested for antichlamydial antibodies by enzyme-linked immunosorbent assay (ELISA) and complement fixation test (CFT). With ELISA, 95 of the 115 sera tested (82.6%) yielded positive antichlamydial reactions. With CFT, 34 of the 119 sera tested (28.6%) were unequivocally positive (> or = 1:10, 100% binding), and 10 (7.6%) yielded doubtful positive reactions (1:10, 50-75% binding). Positive ELISA and CFT titers showed poor agreement (kappa = 0.112), whereas the agreement between positive findings by immunohistochemical labeling and CFT was fair (kappa = 0.205).

Predictors of sudden cardiac death for patients with Chagas' disease: a hospital-derived cohort study.

This study was carried out to identify patients with Chagas' disease at risk of sudden cardiac death, inasmuch as such patients have not been recognized thus far. Seventy-four consecutive patients with a positive complement fixation test for Chagas' disease prospectively followed up at the Cardiomyopathy Clinic from January 1990 to June 1993 were entered into the study. Patients underwent medical history, physical examination, serological tests, resting electrocardiography, chest X-ray and two-dimensional echocardiography. Eighteen of 74 (24%) patients died during the study period, 8 (10%) suddenly and 10 (14%) from pump failure. Sudden death comprised 44% of total deaths. In the univariate model, cardiomegaly in the chest X-ray, left ventricular systolic and diastolic dimension, left ventricular ejection fraction, left atrial dimension and apical aneurysm as detected echocardiographically, and systolic blood pressure were associated with sudden cardiac death. In the multivariate model, however, apical aneurysm and left ventricular diastolic dimension were retained as predictors of sudden cardiac death. We conclude that chagasic patients with apical aneurysm and left ventricular dilation are at risk of sudden cardiac death.

EPIDEMIOLOGY AND IMMUNOGENETICS OF INSULIN-DEPENDENT DIABETES MELLITUS IN VENEZUELAN CHILDREN

We evaluated 91 newly diagnosed IDDM children mean age 7.8 ± 4.5 yrs; 56.7% had had an upper respiratory infection prior to diagnosis and 12.7% had had either mumps or varicella. Peak incidence of disease was found in February and March and August to October. Eighty seven percent had HLA-DR3 and/or DR4 vs 37% of the Venezuelan general population; 81.6% were HLA-DQW2 and/or HLA-DQW8. Studies of oligonucieotid hybridization showed the presence of arginine in position 52 of the DQ alpha chain and absence of aspartic acid in position 57 of the DQ beta chain, with an increased prevalence of DR2 and especially with DQB1 0602 which has been associated with protection. We found 55.9% to have positive islet cell antibodies (ICA) with 4 of these having a positive complement fixation test. Three patients (7.9%) were found to have positive insulin autoantibodies. No positive serotypes for enterovirus (Coxsackie-B) were found in our patients, but we detected 11 cases with elevated titers for cytomegalovirus antibodies. Positive antibodies for measles, mumps, herpes and varicella were found in some children. This study contributes to a better understanding of the epidemiology and immunogenetics of insulin dependent diabetes mellitus in Latin-American children.

Noninvasive Predictors of Mortality for Patients with Chagas&amp;rsquo; Heart Disease: A Multivariate Stepwise Logistic Regression Study

This prospective investigation was conducted in an attempt to identify noninvasive predictors of mortality for patients with Chagas' heart disease through a multivariate stepwise logistic regression study. Fifty-six patients with a positive complement fixation test for Chagas' disease were followed up at the Cardiomyopathy Clinic of our institution from April 1990 to April 1992. Patient age was 59 +/- 17 years; 28 (50%) were male. Upon admission, 19 patients (33%) were in the New York Heart Association (NYHA) class III and 8 (14%) in the NYHA class IV. Systolic blood pressure was 125 +/- 23 mm Hg, diastolic blood pressure 76 +/- 11 mm Hg and resting heart rate 77 +/- 11 beats/min. Forty patients (71%) were given digitalis and 39 (69%) angiotensin-converting enzyme inhibitors. Plasma Na+ was 140 +/- 4 mEq/l, K+ was 4.34 +/- 0.73 mEq/l and creatinine level 1.34 +/- 0.31 mg/100 ml. Cardiomegaly was observed in the chest X-ray of 41 of 51 (79%) available patients. Atrial fibrillation was observed in the resting ECG of 24 of 54 (44%) available patients, premature ventricular contractions in 23 (41%), right bundle branch block in 26 (46%) and left anterior hemiblock in 26 (46%) patients. Echocardiography revealed a left ventricular ejection fraction of 0.45 +/- 0.16, left ventricular systolic dimension of 51.23 +/- 13.53 mm and left ventricular diastolic dimension of 62.94 +/- 19 mm. Sixteen (28%) patients died during the 2-year study, 11 of them suddenly.(ABSTRACT TRUNCATED AT 250 WORDS)

An epidemic ofMycoplasma pneumoniaein Manitoba: A Serological Report

To report an epidemic of Mycoplasma pneumoniae in Manitoba and to discuss the limitations of the serodiagnostic tests used. A retrospective analysis of the results of a province-wide serological testing for respiratory infections caused by M pneumoniae, using a complement fixation test and an indirect immunofluorescent antibody test for the detection of immunoglobulin (Ig) M antibodies. From April 1, 1987, to March 31, 1991, 12,804 sera were tested and a serological diagnosis of recent M pneumoniae infections were established in 509 (3.97%). From April 1 to September 30, 1991, an additional 2088 persons were tested; the 158 (7.5%) recent cases of M pneumoniae were subjected to analysis. Compared with the previous three years, an increase in the number of recent cases of M pneumoniae was first noticed in July 1990 which persisted until September 1991. Of 856 single sera tested, 59 (6.8%) were recent M pneumoniae infections and 56 (96.1%) of these were positive for IgM antibodies. Of the 616 persons who submitted paired sera, 99 (16%) were recent infections, but only 46 (46.4%) had IgM antibodies. Primary infections (ie, positive for IgM antibodies) were detected in 102 (64.5%) and reinfections (ie, positive complement fixation test only) in the remaining 56 persons with recent M pneumoniae infections. Primary infections were detected more frequently in the 'under 16' than in the 'over 16' year age group (75% versus 55.8% of the recent cases of M pneumoniae in each age group). Reinfections were more common in the older age group. Of the 158 recent cases of M pneumoniae, 30.3% had a pneumonia; of these, 21 (55.2%) were under the age of 16 years. M pneumoniae is an important cause of morbidity. Serological tests are used for the diagnosis despite their limitations. The detection of IgM antibodies in acute serum establishes a diagnosis of primary M pneumoniae; however, their absence does not exclude M pneumoniae. A second (convalescent) blood test is required to diagnose all primary infections. To diagnose all reinfections, paired sera should be tested by complement fixation. Manitoba experienced an epidemic of M pneumoniae in 1990-91. Properly selected serological tests can provide a specific and rapid diagnosis.