Comparison of the latex agglutination test and the ergosterol assay for the detection of moulds in foods and feedstuffs

The mould latex agglutination test for the determination of immunogenic extracellular polysaccharides (EPS) produced by moulds was compared with the measurement of ergosterol in foods and feedstuffs with respect to sensitivity and applicability to detection of mould contamination. Both assays were able to detect Penicillium aurantiogriseum and Aspergillus niger at the same stage of growth in liquid and on solid substrates. During incubation, ergosterol and EPS content increased parallel to mould colony count and mycelial dry weight. Growth of Fusaria was detected by the ergosterol assay earlier than by the latex agglutination test. Applicability of the two assays was proved by testing 26 naturally contaminated foods and feedstuffs. From all samples positive results with agglutination titres ranging from 100 to 100 000 and ergosterol contents ranging from 0.6 to 56 mg kg^‐1 were obtained.     

Comparison of an in-house latex agglutination test with IgM ELISA and MAT in the diagnosis of leptospirosis

The laboratory diagnosis of leptospirosis is fraught with several problems. Isolation of Leptospira by culture has a low sensitivity and the microscopic agglutination test (MAT) is time consuming To overcome these problems, a rapid latex agglutination test (LAT) has been standardized for the detection of antileptospiral antibodies in serum samples from suspected cases of leptospirosis. We compared the efficiency of the LAT to a commercially available IgM ELISA and MAT. A total of 150 serum samples were tested by LAT, IgM ELISA, and MAT. The positivity was 26.7%, 26% and 24% respectively. The sensitivity and specificity of LAT as compared to MAT was 90.62 and 91.96% respectively. Even though LAT and ELISA showed similar results, its rapidity and simplicity made latex agglutination test more suitable as a rapid screening test.     

Simple latex agglutination assay for rapid serodiagnosis of human leptospirosis

A newly developed latex agglutination assay for the detection of genus-specific Leptospira antibodies in human sera was evaluated. The assay is performed by mixing, on an agglutination card, serum with equal volumes of stabilized antigen-coated, dyed test and control latex beads and is read within 2 min. The latex agglutination test was evaluated with groups of serum samples from patients with leptospirosis and control patients from Hawaii, the Seychelles, Thailand, and The Netherlands. The mean overall sensitivity was 82.3%, and the mean overall specificity was 94.6%. The assay is easy to perform and does not require special skills or equipment. The reagents have a long shelf life, even at tropical temperatures. Together, these factors make the assay suitable for use even at the peripheral level of a health care system as a rapid screening test for leptospirosis.     

Detection of antibodies to opioid and glutamate receptors by latex agglutination and enzyme immunoassay

We studied adsorption capacity of 5 latexes to synthetic peptide fragments of μ- and δ-opioid receptors and to GluR1 and NR2A subunits of glutamate receptor. Levels of autoantibodies to opioid receptors in the latex agglutination test and enzyme immunoassay were in good correlation. The level of autoantibodies to opioid receptors measured by these methods was increased in patients with opium narcomania, while the content of autoantibodies to the glutamate receptor subunits was increased in epileptics.__________This revised version was published online in July 2005 with the addition of the issue titleTranslated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 139, No. 1, pp. 94–97, January, 2005     

A comparative study on microscopic agglutination test and counterimmunoelectrophoresis for early detection of human leptospirosis

Background and Objectives: Leptospirosis is a potentially fatal bacterial disease that mimics many diseases; therefore, laboratory confirmation is pivotal. Though microscopic agglutination test (MAT) is accepted as World Health Organisation (WHO) reference test, it has got many pitfalls such as being hazardous, tedious, cumbersome and expensive. Counterimmunoelectrophoresis (CIE) is popularly used for diagnosing many infectious diseases but rarely for Leptospirosis. The aim of this study is to find suitability of CIE for the routine laboratory diagnostic purposes. Materials and Methods: Repeat sampling (paired sera) was possible from 401 subjects of which 181 were in-patients of Salem Government General and Private Hospitals and the remaining 220 MAT negative healthy College students gave their consent for the study. All the 802 sera samples were collected from January 2009 to November 2012 and subjected to the present study. After carrying out MAT and CIE on the suspected and control samples, a comparative evaluation was conducted. McNemars test method was used to find out the significant difference between the two tests in the early diagnosis. Result: The sensitivity, specificity, Positive Predictive value (PPV), Negative Predictive value (NPV) and Efficiency test for CIE were 96.80%, 89.28%, 95.23%, 92.59% and 94.47%, respectively. The corresponding values for MAT were 95.90%, 89.83%, 95.08%, 91.37% and 93.92%, respectively. There was no significant difference between MAT and CIE at 95% and 99% confidence intervals according to McNemars test. P value in the early stage of illness was greater for CIE than MAT when Polymerase Chain Reaction (PCR) was used as Gold Standard of diagnosis. Interpretation and conclusion: It was concluded that the CIE could be advantageous over MAT due to its safety, rapidity, simplicity, economic and easy for large number of samples. It can answer little earlier than MAT and found as reliable as that of MAT. Since both the tests had shown similar efficacies in the later stage of the illness, the importance could be given to CIE due to early diagnosis.     

Development and preliminary evaluation of a slide latex agglutination assay for detection of Clostridium perfringens type A enterotoxin

A slide latex agglutination (SLA) assay was developed for rapid screening for Clostridium perfringens type A enterotoxin (CPE). SLA specifically detected CPE added to buffer or normal feces (sensitivity limit of 1 μg CPE/g feces). Using clinical fecal samples from C. perfringens food poisoning cases, a strong correlation was shown between (1) SLA results and results from other CPE assays and (2) between SLA results and illness status.     

A reverse passive latex agglutination test for the diagnosis of systemic candidosis

A new reverse passive latex agglutination test for the detection of serum antigen in systemic Candida albicans infection is reported. 1700 sera were examined from 91 patients who had either proven or suspected systemic candidosis, 183 patients who were colonized and 636 patients with no evidence of candidal infection. Thirty of the systemically infected patients had lymphoproliferative disorders and the rest a variety of surgical or medical diseases with no underlying neutropenia. The latex particles were sensitised with an antiserum raised in rabbits against a pressate of Candida albicans. The degree of antigenaemia was proportional to the likelihood of invasive disease such that a diagnostic cut-off point of 1 in 8 produced a test for systemic candidosis with a sensitivity of 90% and specificity of 80.4% in patients with lymphoproliferative disorders. In the remaining medical and surgical patients a diagnostic cut-off point of 1 in 10 produced a test with a sensitivity of 96.7% and specificity of 98.8%. The patients with lymphoproliferative disorders tended to produce lower serum antigen levels. The sera were also assayed for antibody using latex particles sensitised with pressate.     

Rapid detection of rotavirus in stool by latex agglutination: comparison with radioimmunoassay and electron microscopy and clinical evaluation of the test

A latex agglutination test (LX) using antisera prepared against Nebraska calf diarrhea virus (NCDV) is described for the detection of rotavirus in stool of children with acute gastroenteritis. The test was compared with electron microscopy (EM) and radioimmunoassay (RIA) with 100 stools positive or negative for rotavirus. Out of 53 stools positive in RIA or EM, 49 were positive in LX and 4 were negative. Two specimens negative in EM and RIA were falsely positive in LX. The method was also tested in two clinical series with 115 stools from 101 children. Altogether 67/115 stools were positive in RIA, and 62/115 in LX. Out of 7 stools with contradictory results, 6 were negative in LX but positive in RIA, and 1 was positive in LX but negative in RIA. The results indicate that the LX is suitable for rapid screening of rotavirus gastroenteritis in clinical practice.     

Suitability of dyed latex bead agglutination test for immunodiagnosis of Karnal bunt (Tilletia indica) teliospores in a single seed of wheat

The immunodiagnosticum for this test was prepared extempore by mixing blue color dyed latex beads (1% suspension) with equal volume of diluted anti-teliospore serum. This test was considered to be better for the detection of solubilized teliosporic antigens over intact teliospores of Karnal bunt. The teliosporic antigens solubilized using sonication and detergent extraction were used for the standardization of the test by optimizing the dilution of latex bead suspension and determining the detection limits. For determining the sensitivity of test, antigen concentration kinetics analysis was performed by adding 15 µl of antibodies sensitized latex beads to 15 µl of different concentrations of solubilized antigens on glass slide. The detection limit of this test was 7.5 µg solubilized teliosporic antigens equivalent to 750 teliospores and suitable for single seed analysis. Small agglutinin formation with solubilized antigen of Puccinia recondita and T. barclayana interpreted on the basis of partial cross reactivity of immunodignosticum with these pathogens. However, no cross reactivity was found with teliosporic antigen(s) of spores of Curvularia lunata, Ustilaga tritici, Helminthosporium sativum, Ustilaginoidea vircns and Alternaria triticina.     

Latex agglutination test for adenovirus diagnosis in diarrheal disease

A commercial latex agglutination test for diagnosis of adenovirus in diarrheal disease (Adenolex, Orion Diagnostica, Finland) was evaluated by comparison with the results obtained by ELISA, electron microscopy (EM), and virus isolation. Fifty specimens originated from the diagnostic routine, and 50 were selected from a previous epidemiological study on the etiology of diarrheal disease in children. Thirteen of the 100 specimens reacted with the latex control, impairing interpretation of the results. Although the ELISA detected adenovirus antigen in 10(2) higher dilutions than the latex agglutination test, a total agreement was obtained between results by the two tests for 87 specimens including 42 positives. The two additional positives found by EM and virus isolation could not be diagnosed by the latex agglutination test. Of 37 specimens containing enteric adenoviruses (types 40 and 41), the agglutination test diagnosed all but 4 specimens containing type 41 virus. These four specimens were negative also by ELISA and adenovirus had been detected by virus isolation on the 293 cell line. The latex agglutination test gave positive results with nine specimens containing adenovirus types other than the enteric types 40 and 41. The latex agglutination test was found to be a rapid and simple method for the detection of adenovirus in diarrheal disease. Compared to ELISA and EM, the sensitivity was 100% and 95% respectively, and the specificity 100%.     

A critical analysis of commercially available latex particle reagents for C-reactive protein (CRP) slide agglutination tests

C-reactive protein (CRP) was assessed in pediatric serum samples using different commercial latex reagents, which were analyzed for species origin of the coating antibodies, homogeneity and density of the latex particles, and prozone agglutinating capacity. All reagents correctly agglutinated the positive and negative control sera. The antibodies coating the particles differed with regard to species origin: one was coated with rabbit, one with horse and goat, one with horse, goat, rabbit and swine, while the reference reagent had horse, goat and rabbit antibodies.Only the monospecies specific antibody-coated latex showed obvious prozoning; this reagent also had the smallest and most homogenous latex particles and showed the most clear-cut reactions. False agglutination was observed at 7–26% according to quantitation with the spot immunoprecipitate assay, which compared favorably with radial immunodiffusion measurements. The lowest percentage of false readings was noted for the rabbit antibody-coated particles; the highest for the reagent with particles coated using antibodies from 4 different species.No reagent had satisfactory precision for the low positive sera between 10 and 40 mg CRP/1.     

Rapid typing of the human neutrophil antigen 1a by the particle gel agglutination assay

The human neutrophil antigen 1a (HNA-1a) plays a major role in immune neutropenias and transfusion-associated lung injury. In this study, we describe a simple and rapid particle gel agglutination assay (PaGIA) for HNA-1a phenotyping. A commercially available monoclonal antibody (MoAb) to HNA-1a was biotinylated and coupled onto superparamagnetic streptavidin particles. Diluted anticoagulated whole blood samples from healthy blood donors ( n  = 147) were incubated with MoAb-coated particles, washed, transferred into an ID-gel card, and, subsequently, centrifuged. HNA-1a-positive samples resulted in a visible agglutination of the particles on top of the gel column and could be evaluated macroscopically. The results obtained by the new test were identical with those obtained by the polymerase chain reaction–sequence-specific priming technique that was performed in parallel. Seventy-four (50.3%) of the 147 samples were found to be HNA-1a positive. The HNA-1a PaGIA is both simple and safe and can be implemented in various laboratory settings.     

Performance of commercial latex agglutination tests for the differentiation of Candida dubliniensis and Candida albicans in routine diagnostics

Candida dubliniensis is phenotypically similar to Candida albicans and may therefore be underdiagnosed in the clinical microbiology laboratory. The performance of Bichro-Dubli latex agglutination test for rapid species identification of C. dubliniensis was prospectively evaluated on 111 vaginal and 118 respiratory isolates. These had presumptively been identified as C. albicans/C. dubliniensis by their green colonies on CHROMagar Candida plates. Bichro-Dubli test identifed 2 (1.8%) vaginal and 6 (5.1%) respiratory isolates as C. dubliniensis. The test was also positive for 37 C. dubliniensis control strains characterised by 18S-28S DNA-sequencing. Bichro-Dubli test is thus a sensitive and accurate tool for rapid diagnostics in routine laboratories.     

Evaluation of recombinant leptospiral surface antigen (Lsa27) lipoprotein for serodiagnosis of human leptospirosis by latex agglutination test

PurposeLeptospirosis has wide clinical presentations often mimicking other illnesses, thus rapid and simple diagnostics will have facilitated the initial patient management and therapy compared to other inaccessible and laborious tests/assays.MethodIn this study, the sensitized latex beads coated with purified recombinant outer membrane (OM)-leptospiral surface antigen (Lsa27) lipoprotein of pathogenic Leptospira was evaluated as a diagnostic antigen in latex agglutination test (LAT) for the detection of anti-leptospiral antibodies in the human sera. The prepared rLsa27 latex beads were evaluated with the confirmed microscopic agglutination test (MAT) reactive (at 1:50) Leptospira-specific positive (n = 42) and non-reactive negative (n = 80) sera from human cases suspected of leptospirosis with the history of pyrexia of unknown origin.ResultThe results revealed the relative diagnostic sensitivity of 90.48 % (confidence interval (CI) at 95 % : 77.4–97.3 %) and diagnostic specificity of 91.35 % (CI at 95 %: 82.8–96.4 %), with an accuracy of 90.98 % (CI at 95 %: 84.44–95.41 %), and the kappa value of 0.8036 ± 0.056 SE (CI at 95 %: 0.69–0.91) with a substantial agreement against gold standard serological MAT.ConclusionThe findings suggest that the rLsa27 protein-based LAT can be useful as a simple rapid screening diagnostic test for the detection of anti-leptospiral antibodies in the sera of humans. This rapid test can be complemented by other confirmatory diagnostics for the early detection of Leptospira antibodies which may in turn help in the prompt treatment and mitigates the public health problem at primary health care level.     

A latex agglutination test using a recombinant nucleoprotein for detection of antibodies against avian influenza virus

A latex agglutination test (LAT) was developed for detecting antibodies against avian influenza virus. The recombinant avian influenza virus nucleoprotein expressed in Escherichia coli was purified, coupled with latex beads, and used as an antigen for the LAT. The LAT was capable of detecting anti-avian influenza virus antibodies irrespective of the avian-influenza subtype, and in most cases, the results correlated with the results of an agar gel precipitation test (AGPT). However, in comparison with the AGPT, the LAT could detect the anti-avian influenza virus antibodies for a longer period of time after the infection. The nonspecific agglutination observed in uninfected chicken sera was resolved by pretreating the sera with dried chicken-liver powder for 1 h. The LAT is easy to perform, and even after considering the time required for pretreatment of the serum, the total time required for obtaining the results is reduced in comparison to the time required in the case of the AGPT. This easy and rapid LAT is considered to be useful for monitoring avian influenza virus infection in the field.     

Latex particle agglutination test as an adjunct to the diagnosis of bacterial meningitis

The present study aimed to review the results of microscopic examination, routine culture and antigen detection by latex particle agglutination test (LPAT), in order to evaluate the diagnostic value of the LPAT in establishing the aetiological diagnosis of bacterial meningitis. LPAT was done in 65 clinically suspected meningitis cases ranging from 5 days to 60 years of age and was compared with culture and Gram stain. Using LPAT, an aetiological diagnosis could be done in 10 out of 65 (15.4%) cases of bacterial meningitis. In contrast, Gram stain and culture showed 16.9 and 23.1% positivity, respectively. LPAT correlated well with Gram stain and culture and can be recommended as an adjunct laboratory test for rapid aetiological diagnosis of bacterial meningitis for prompt institution of proper antibiotics.     

Latex Test System for Rapid Diagnosis of Leptospira Infection

A diagnostic test system based on polymer latex carriers sensitized by IgG to Canicola and Icterohaemorrhagiae serogroup Leptospira was developed and tried.__________Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 139, No. 5, pp. 544–549, May, 2005     

Rapid identification of Burkholderia pseudomallei in blood culture supernatants by a coagglutination assay

In total, 309 blood culture supernatants were tested for the presence of Burkholderia pseudomallei antigen using an in-house coagglutination test prepared by sensitising Cowan I staphylococcal cells with B. pseudomallei polyclonal antiserum. The coagglutination test gave a sensitivity, specificity, positive predictive value and negative predictive value of 100% in comparison with blood culture. A subset of 102 supernatants was also tested for B. pseudomallei antigen using a monoclonal antibody-based latex agglutination test. The sensitivity, specificity, positive predictive value and negative predictive values of this test were 100%, 90%, 75% and 100%, respectively.     

Development and evaluation of a latex agglutination test for the serodiagnosis of paracoccidioidomycosis

Paracoccidioidomycosis (PCM) is the most prevalent systemic mycosis in Latin America. It is caused by the dimorphic fungus Paracoccidioides brasiliensis. The immunodiffusion (ID) test is one of the most widely used techniques for PCM serologic diagnosis due to the simplicity and low costs of its execution. However, it requires trained and qualified people to execute it. The purpose of this study was to evaluate a latex particle agglutination (LA) test for the detection of anti-P. brasiliensis antibodies by using pooled crude exoantigens from the fungus. Fifty-one serum samples obtained from patients with PCM were tested. Positivity was observed in 84% (43/51) of these patients, and the agglutination patterns varied from small clumps with a cloudy background to large clumps with a clear background. The antibody titer reactivity ranged from 1:2 to 1:64. Cross-reactivity was observed in sera from patients with aspergillosis, histoplasmosis, and nonfungal disease. Serum samples obtained from healthy donors were not reactive. The sensitivity and specificity of the LA test were 84% and 81%, respectively. When comparing the LA test with the double-immunodiffusion test, we found an agreement of 92%. Further work is needed to improve the performance of the LA assay before it can be proposed as a reliable diagnostic tool, mainly in laboratories with little infrastructure.     

Rapid and reliable identification of Staphylococcus aureus by a latex agglutination test

A latex slide agglutination test detecting clumping factor and protein A simultaneously is recommended for rapid and reliable routine identification of Staphylococcus aureus. Strains (836) of staphylococci isolated from clinical specimens were examined, all S. aureus strains identified by conventional methods were correctly differentiated by the latex test, and no false-positive results occurred with other staphylococci. The reagent is easy to prepare since plasma is the coating material.