Latex Agglutination Test For Detection Research Articles

Comparative analysis of diagnostic methods for the detection of Cryptococcus neoformans meningitis.

Cryptococcosis is a devastating opportunistic infection in immunocompromised individuals, primarily in people living with HIV/AIDS. This study evaluated a protocol for the early diagnosis of meningitis due to C. neoformans, utilizing established molecular techniques from serum and CSF samples. The 18S and 5.8S (rDNA-ITS) sequence-specific nested PCR assays were compared with direct India ink staining and the latex agglutination test for detection of C. neoformans in serum and cerebrospinal fluid (CSF) from 49 Brazilian suspected meningitis patients. Results were validated with samples obtained from 10 patients negative for cryptococcosis and HIV, and by analysis of standard C. neoformans strains. The 5.8S DNA-ITS PCR was more sensitive (89-100%) and specific (100%) than the 18S rDNA PCR and conventional tests (India ink staining and latex agglutination) for identification of C. neoformans. While the 18S PCR exhibited a sensitivity (72%) similar to that of the latex agglutination assay in serum samples, it was superior to the latex agglutination assay when testing CSF, with a sensitivity of 84%. However, the latex agglutination was superior to the 18SrDNA PCR in specificity in CSF (92%). The 5.8S DNA-ITS PCR yielded the highest levels of accuracy (96-100%) of any test for detection (serological and mycological) of C. neoformans in both serum and CSF. Use of the nested 5.8S PCR was superior to other techniques for the diagnosis of cryptococcosis. The possibility of using serum, a non-invasively collected material, in a targeted 5.8S PCR analysis to identify Cryptococcus spp. is recommended, especially in immunosuppressed patients. Our results indicate that nested 5.8S PCR can increase the diagnostic capability of cryptococcosis, and we suggest its use to monitor patients in the future.

Evaluation the latex agglutination test for detection of the causative agents of bacterial mastitis in milk samples

Mastitis is the main disease in dairy farms that causes serious losses. The early diagnosis and specific treatment can prevent the spread of the disease and the economic losses. The aim of this study was to evaluate the accuracy of the latex agglutination assay for detection of the main bacterial mastitis agents. The antiserum against Staphylococcus aureus, Trueperella pyogenes, Streptococcus agalactiae and Escherichia coli were prepared from immunized rabbits. The couplings of antibodies to latex particles were optimized and after that, the limit of detection (LOD) of latex agglutination test was evaluated for detection of the mentioned bacteria. The detection limit for the Streptococcus agalactiae, E. coli, Staphylococcus aureus and T. pyogenes were respectively 1.3×103, 2×107, 1.58×104 and 5.4×104 colony-forming unit per each milliliter of the bacterial suspensions. The prepared latex test has more sensitivity in the setting of phosphate buffered saline than in contaminated milk samples. This method can be used for the fast detection of the mentioned bacteria in bacterial cultures and milk samples. The latex agglutination test could be evaluated as a fast, cost benefit, and practical method in dairy farms.

Sensitivity and specificity of a latex agglutination test for detection of calf enterotoxigenic Escherichia coli isolates in comparison with PCR

Latex agglutination test is a very fast, accurate, and specific method that is used to diagnose antigens and antibodies which can be carried out in any place without need for any specific devices. In the present study, a single chain (scFv) recombinant monoclonal anti-K99 antibody was used in designing and producing a latex agglutination kit for the detection of enterotoxigenic Escherichia coli of calves colibacillosis. The purpose of this research was to primarily evaluate the sensitivity and specificity of the mentioned latex agglutination kit in the detection of the considered bacteria and to compare it with the results of PCR method. To carry out latex agglutination method, carboxyl latex particles were covered by the recombinant monoclonal antibodies of anti-K99 scFv. Then, these latex particles were mixed with the bacterial suspension purified from the diarrhea samples of the calves on the black cards of kit to observe agglutination. Sensitivity and specificity of the latex agglutination kit in the diagnosis of this colonization factor was evaluated and compared with the results of PCR test. Comparison of the PCR test results with those of the kit indicated that, under the laboratory conditions and on the purified bacteria, sensitivity and specificity levels of the latex agglutination kit were 100 and 96 %, respectively. Primary evaluation showed that the new latex agglutination kit was able to quickly diagnose the K99+ bacteria and can be used for the detection of calves colibacillosis.

Evaluation of different methods to detect methicillin resistance in Staphylococcus aureus (MRSA)

The studies suggest that dogs living with human are potential risk of becoming MRSA carrier and increased risk of infections caused by MRSA. Phenotypic methods to detect methicillin resistance in Staphylococcus aureus (MRSA) are inadequate. The objective of the present study was to determine methicillin resistance in S. aureus by phenotypic susceptibility test (oxacillin disk diffusion, cefoxitin disk diffusion, oxacillin screen agar) and molecular methods (PCR as a gold standard) and the latex agglutination test for the detection of PBP2a and to evaluate the results of these tests for its sensitivity and specificity. A total of 100 swab samples were taken from muzzle site, in more contact with human, of dogs and MRSA were isolated. Oxacillin (1 μg), cefoxitin (30 μg) disk diffusion and oxacillin screen agar method were used. The isolates were also subjected to latex agglutination test for detection of PBP2a and PCR to detect mecA gene. By PCR 37% of isolates show the presence of mecA. Latex agglutination was found to be the most sensitive (97.29%) and cefoxitin disk diffusion to be the most specific (96.82%) tests for detection of MRSA. Our finding showed that combining oxacillin screen agar or cefoxitin disk diffusion with latex agglutination improves sensitivity and specificity to detect methicillin resistance S. aureus (MRSA) isolates.

The rise and fall of epidemic Neisseria meningitidis from a tertiary care hospital in Delhi, January 2005–June 2007

Meningococcal meningitis is endemic in India. There has been a sudden surge of cases of meningococcal meningitis in 2005 in Delhi. Present study was undertaken to find out changing trends in incidence of this disease from a tertiary care hospital in New Delhi over a period of two and half years. All samples from suspected cases of meningococcal meningitis were subjected to Gram staining, culture and latex agglutination test for detection of Neisseria meningitidis (N.meningitidis). Antimicrobial susceptibility of all isolates was performed using the disc diffusion test. 78.6%, 71.4% and 100% of the samples were positive for N.meningitidis by smear examination, culture and latex agglutination test respectively. Except for resistance to Penicillin and Erythromycin in 8.8% and 5.9%, the isolates were sensitive to the commonly used antibiotics. Using simple, rapid and reliable methods for diagnosis, defining risk factors and continuing surveillance remain important public health goals for the control of meningococcal disease.

Seropositivity rates for Bartonella henselae, Toxocara canis and Toxoplasma gondii in New Zealand blood donors

Bartonella henselae, Toxocara canis and Toxoplasma gondii organisms can all cause vision-threatening posterior segment disease. Diagnosis relies heavily on clinical findings, but detection of antibodies in the patient's serum may be helpful in some cases. The significance of a positive serology result depends on the seroprevalence in the general population. Seroprevalence rates for these organisms vary widely around the world and this study aimed to determine the rates for a New Zealand population. One hundred and forty healthy blood donors from the Waikato region in the North Island of New Zealand had their serum tested using an indirect latex agglutination test for detection of T. gondii antibodies, an indirect immunofluorescent assay for B. henselae antibodies and an enzyme-linked immunosorbent assay test for T. canis antibodies. Seropositivity rates for T. canis, T. gondii and B. henselae in this New Zealand population were 0.7 +/- 1.65%, 42.9 +/- 8.12% and 5 +/- 3.61%, respectively. Seropositivity rates for T. gondii and B. henselae in New Zealand are similar to rates reported in some other countries; however, T. canis seroprevalence may be lower than reported elsewhere in the world.

Serum and plasma latex agglutination tests for detection of fibrin(ogen) degradation products in clinically ill dogs.

An increased concentration of fibrin(ogen) degradation products (FDPs) commonly is used in conjunction with other hemostatic test abnormalities to identify patients with disseminated intravascular coagulation (DIC). Positive FDP results, however, have been observed in dogs without clinical evidence of DIC. The purpose of this study was to evaluate FDP concentrations in a group of clinically ill dogs with a variety of disorders. Dogs included in the study had the following hemostatic parameters evaluated: prothrombin time, activated partial thromboplastin time, fibrinogen concentration, platelet count, and FDP concentration. Two rapid latex agglutination methods were compared for detecting FDP in serum samples (Thrombo-Wellcotest, International Murex Technologies Corp) and plasma samples (FDP Plasma, American Bioproducts Inc). Results of the serum FDP method were positive in 8% (4/50) of the dogs tested: 3 with DIC and 1 with immune-mediated hemolytic anemia and liver disease. Results of the plasma FDP test were positive in 60% (30/50) of the animals tested: 6 with DIC, 3 with confirmed thrombosis, and 21 with a variety of conditions, including neoplasia, immune-mediated hemolytic anemia, pancreatitis, gastric dilatation-volvulus, heat stroke, severe trauma, sepsis, protein-losing nephropathy, liver disease, hyperadrenocorticism, and chronic heart failure. Because the plasma FDP test was positive more frequently than the serum FDP test in ill dogs, it may be more sensitive for the detection of canine FDP.

Lack of sensitivity of the latex agglutination test to detect bacterial antigen in the cerebrospinal fluid of patients with culture-negative meningitis.

For culture-negative meningitis, use of the latex agglutination test for detection of bacterial antigen in the CSF has a sensitivity of only 7%. Routine use of the latex agglutination test may not contribute to the management of suspected acute bacterial meningitis, since patients are treated on the basis of their clinical presentations and CSF findings.

A rapid latex agglutination test for detection of leptospiral antibodies

A rapid semi-quantitative latex agglutination test (LAT) has been standardized for the detection of leptospiral antibodies in serum samples of man and animals. The efficacy of the LAT was compared with the plate enzyme linked immunosorbent assay (ELISA). A total of 276 human serum samples were analyzed by both LAT and ELISA and percentage positives were 84.8 and 85.9%, respectively. Similarly, of 65 animal samples tested, 63.1 and 69.2% positivity were observed in LAT and ELISA, respectively. Even though the ELISA test was slightly more sensitive than LAT, the rapidity, simplicity and economics of the LAT were found to fulfill the requirements of a screening test for leptospiral antibodies.

Improved latex agglutination test for detection of antibodies in serum and cerebrospinal fluid of Trypanosoma brucei gambiense infected patients

A rapid latex agglutination test (LATEX/ T. b. gambiense) for detection of antibodies in patients infected with Trypanosoma brucei gambiense is presented. The reagent is coated with a mixture of three variable surface antigens of bloodstream form trypanosomes. Two hundred and forty sera and 79 CSF samples from patients with parasitologically confirmed trypanosome infection along with 173 sera and 38 CSF samples from non-trypanosomiasis patients have been tested. At 1:16 serum dilution, test specificity was 99%, while sensitivity ranged from 83.8 to 100% depending on the geographical origin of the samples. Undiluted CSF samples from non-trypanosomiasis and from first stage patients scored negative while 42 out of 66 CSF samples from second stage patients were positive. Stability and reproducibility of the lyophilized reagent were excellent.

Detection of Trypanosoma brucei, T. congolense and T. vivax infections in cattle, sheep and goats using latex agglutination

A monoclonal antibody-based latex agglutination test for detection of circulating trypanosome antigens in animal serum was evaluated for the ability to detect natural T. brucei, T. congolense and T. vivax infections in cattle, sheep and goats in Ghana. The test detected antigens in 180 422 (42.7%) of cattle, 27 131 (20.6%) of sheep and 14 79 (17.7%) of the goats. By comparison, the microplate-based antigen-ELISA gave similar results ( P>0.01), detecting trypanosome antigens in 41.7% of the cattle, 19.8% of the sheep and 17.7% of the goats. Trypanosomes were demonstrated in the blood of 30 (7.2%) cattle, 7 (5.3%) sheep and 3 (3.8%) goats using the buffy coat technique (BCT). Of these, 26 cattle (86.7%), 6 sheep (85.7%) and all 3 goats (100%) were antigenaemic. The most prevalent single infection in all 3 animal species involved T. vivax, and the most common mixed infection involved all 3 trypanosome species in cattle and sheep. There was no mixed infection in goats. Compared with the antigen-ELISA, the sensitivity of the latex agglutination test was 98.3% in cattle and 100% in both sheep and goats, whilst the specificity was 97.2% in cattle, 99% in sheep and 100% in goats. False positivity with the latex agglutination test was 3.9% in cattle and 3.7% in sheep. There were no false-positive reactions with the test in goats. The latex agglutination assay promises to be ideal for testing small numbers of animals under field conditions.

Evaluation of new monoclonal antibody-based latex agglutination test for detection of cryptococcal polysaccharide antigen in serum and cerebrospinal fluid

We evaluated the performance of CRYPTO-LEX (Trinity Laboratories, Inc., Raleigh, N. C.), a new mouse immunoglobulin M monoclonal antibody latex agglutination reagent which reacts with the capsular polysaccharide of the four serogroups of Cryptococcus neoformans. This test was compared with CALAS (Meridian Diagnostics, Cincinnati, Ohio) for the ability to detect cryptococcal antigen in serum and cerebrospinal fluid (CSF). A total of 580 clinical specimens (327 serum and 253 CSF samples), primarily from human immunodeficiency virus-infected patients, were tested in this study. Sixty-seven specimens (44 serum and 23 CSF samples) were positive for cryptococcal antigen with both tests, and 511 (282 serum and 229 CSF samples) were negative. The two latex reagents agreed for 326 of 327 serum specimens (44 positives and 282 negatives). One serum specimen with a titer of 1:2 was CALAS positive but CRYPTO-LEX negative. The titer correlation coefficient for the two tests was 0.884 when two highly discordant serum specimens were eliminated from analysis of the data. The two latex tests agreed for 252 of 253 CSF specimens (23 positives and 229 negatives). One specimen with a titer of 1:2 was positive with CALAS and negative by CRYPTO-LEX. The correlation coefficient of the two tests for CSF titers was 0.886. The sensitivity and specificity of CRYPTO-LEX were 97 and 100%, respectively, with a 99.6% correlation with CALAS. These data show that the performance of CRYPTO-LEX is comparable to that of CALAS for detection of cryptococcal antigen in serum and CSF.

Evaluation of new monoclonal antibody-based latex agglutination test for detection of cryptococcal polysaccharide antigen in serum and cerebrospinal fluid.

Evaluation of new monoclonal antibody-based latex agglutination test for detection of cryptococcal polysaccharide antigen in serum and cerebrospinal fluid.

Comparison of Enzyme Immunoassay and Latex Agglutination Test for Detection of Cryptococcal Antigens.

Comparison of Enzyme Immunoassay and Latex Agglutination Test for Detection of Cryptococcal Antigens.

Evaluation of a commercial latex agglutination test for rapid detection of salmonella in fecal samples

A latex agglutination test for the detection of salmonella in feces was evaluated in comparison to direct culture and enriched culture using both artificially inoculated samples and clinical samples. In the samples inoculated artificially with different concentrations of salmonella (10(1) to 10(5) per gram) the enriched culture performed better only at the 10(2) level in 0.4 g samples, whereas the latex test performed as well as the enriched culture at all levels in 4 g samples. In the tests using clinical samples, there was no significant difference between results of the latex test performed in 2283 samples and the enriched culture performed in 2072 samples. The sensitivity, specificity and negative and positive predictive values of the latex test were 88.2%, 98%, 97.5% and 63% respectively. The test provided results rapidly but yielded a number of false positive results.

Latex agglutination test for detection of mutans streptococci in relation to dental caries in children

A simple and rapid system based on a latex agglutination (LA) reaction was devised for the detection of mutans streptococci in dental plaque. Latex particles were sensitized with antibodies against whole cells of Streptococcus mutans strains MT8148 (serotype c), MT703R ( e) and OMZ175 ( f) and Strep. sobrinus strains B13 ( d) and 6715 ( g). These sensitized particles were agglutinated within a few minutes after addition of 1.0–10ng serotype-specific antigen from the homologous organisms or the nitrous acid extract of whole cells at 10 5–10 6c.f.u. The LA test specifically differentiated not only mutans streptococci from the other oral streptococci but also Strep. sobrinus from Strep. mutans. The LA test was also applicable to extracts of plaque from 206 human subjects who harboured mutans streptococci. In clinical trials, the outcome of the LA test correlated significantly with the number of mutans streptococci found in plaque ( p < 0.0001), which was quantified by the selective cultivation of mutans streptococci. Furthermore, the LA test discriminated between Strep. mutans and Strep. sobrinus from human dental plaque. The sensitivity and the specificity of the LA test for detection of mutans streptococci were 78.9 and 100%. The degree of reactivity in the LA test correlated significantly with the number of decayed tooth surfaces ( p < 0.0001) and decayed and filled tooth surfaces ( p < 0.0001). These results suggest that the LA test could be useful clinically for the detection of mutans streptococci in dental plaque as well as serving as a caries-activity test.

A Rapid Latex Agglutination Test for Detection of Antibodies in Tuberculosis and Hansen's Disease

Antigens of Mycobacterium w, a saprophytic fast growing organism having antigenic epitopes cross-reactive with Mycobacterium leprae and Mycobacterium tuberculosis, were coated on to latex beads (0.33 micron Zn size), and the reactivity tested with sera of tuberculosis and Hansen's disease (HD) patients. Seventy nine percent of lepromatous leprosy (LL) and eighty five percent of pulmonary tuberculosis (TB) patients sera showed an agglutination reaction easily read by naked eye. Specificity of the test was further checked by testing sera of non-mycobacterial infection cases and all of them were found negative. Among apparently healthy controls, 4.3% were found positive from non-endemic and 8.8% from endemic area. The sensitivity of the assay is further enhanced from 78.7% to 90.4% and 85.7% to 91.6% in both LL HD and pulmonary tuberculosis respectively, by using immune complexes extracted from the patients sera. Potential of these antigen coated beads to detect the two major human mycobacterial disease, LL HD and pulmonary TB was also put evidence in a double blind study on coded sera samples obtained from various hospitals in India. The antigen coated beads are stable for upto 6 months at 4 degrees C. The latex slide agglutination test reported here, is simple, rapid, easy to perform and can be used even in rural areas of developing countries.

Evaluation of a new tube latex agglutination test for detection of type-specific pneumococcal antigens in urine

A modified tube agglutination test using type-specific latex reagents for detection of pneumococcal capsular polysaccharide antigens in alkalinized, unconcentrated urine samples was evaluated in reconstituted urine samples and in groups consisting of 26 children with clinical and roentgenographic evidence of acute lower respiratory tract infection, six patients with blood culture-proven infection of nonpneumococcal etiology, and 30 healthy individuals. The sensitivity of the tube latex agglutination method for pneumococcal polysaccharides was 2 to 10 times higher than that of the slide agglutination method. Positive antigen findings were obtained for 42% of urine samples from patients with acute lower respiratory tract infection but in neither patients with nonpneumococcal septicemia nor healthy controls. Fifty-five percent of the antigen-positive patients also showed evidence of pneumococcal involvement by pneumococcal antibody assay or antigen detection in acute-phase serum.

The Lack of Utility of the Latex Agglutination Test for Detection of Candida Antigen in the Diagnosis of Systemic Candidiasis

The Ramco latex agglutination test in the diagnosis of systemic candidiasis was utilized for 11 serum samples from 10 patients with systemic candidiasis, 21 serum samples from patients colonized with Candida species, and 20 control serum samples from patients with stable medical problems and no evidence of Candida albicans infection. This study was double-blind and the results of the latex agglutination test did not influence the decision for antifungal therapy. Nine of 10 patients with systemic candidiasis had positive titers (greater than or equal to 1:4); however, these were determined only 1 to 5 days before culture positivity. Nine of 21 (43%) of colonized patients were falsely positive (greater than or equal to 1:4) and all of the control samples were negative. The Ramco latex agglutination test was unreliable and inconsistent in this small sample group to establish an early diagnosis of systemic candidiasis.

Evaluation of a new latex agglutination test for detection of streptolysin O antibodies

Acute- and convalescent-phase serum specimens were collected from 50 patients with group A streptococcal pharyngitis. The anti-streptolysin O (ASO) titer for each serum specimen was determined by using both the standard neutralization assay and the latex agglutination (LA) test (Rheumagen ASO; Biokit Inc., New Britain, Conn.). When the ASO titers derived by the two methods were compared, the correlation coefficient was 0.93. When the ability of the LA test to demonstrate a significant ASO titer rise (greater than or equal to 2 dilutions) was compared with that of the standard neutralization assay, the LA test had a sensitivity of 91%, a specificity of 86%, a positive predictive value of 83%, and a negative predictive value of 92%. Triplicate LA test determinations were performed on a subset of 31 serum specimens, and for 29 (94%), the repeated ASO titers were all within 1 dilution of each other; the width of the 95% confidence interval for the triplicate measurements of each serum specimen was +/- 32.8 IU. We found the Rheumagen ASO to be a simple, rapid LA procedure for measuring ASO titers that produces results that are highly reproducible, show little lot-to-lot variability, and are comparable to the ASO titers obtained with the standard neutralization assay.