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Detection of enterotoxigenicity of Staphylococcus aureus strains: a comparative use of the modified Ouchterlony precipitation test, reversed passive latex agglutination test, and avidin-biotin ELISA.

The avidin-biotin enzyme-linked immunosorbent assay (ELISA), reversed passive latex agglutination (RPLA) test, and the modified Ouchterlony precipitation test (MOPT) were compared in detecting enterotoxin production by Staphylococcus aureus strains. A total of 1015 strains isolated from human beings, animals, and foods were tested for staphylococcal enterotoxins A (SEA), B (SEB), and C (SEC). Of these, 495 (48.8%), 467 (46.0%), and 204 (20.1%) were classified as enterotoxigenic by the ELISA, RPLA test, and MOPT, respectively. The difference in the number of strains classified as enterotoxigenic by the ELISA and RPLA test was not significant (P > or = 0.05; chi 2), but both tests detected significantly (P < 0.001; chi 2) more enterotoxigenic strains than the MOPT. The combined use of the three assay systems classified 258 (25.4%), 278 (27.4%), and 263 (25.9%) of 1015 strains tested as positive for SEA, SEB, and SEC, respectively. However, the three systems were all positive in only 29.1% of SEA-producing strains, 32.0% of SEB-producing strains, and 25.1% of SEC-producing strains. The MOPT was negative when the corresponding ELISA and RPLA test were positive (46.9% for SEA, 43.5% for SEB, and 40% for SEC); the RPLA test was negative when the corresponding ELISA was positive (10.5% for SEA, 15.5% for SEB, and 25.5% for SEC); and the ELISA was negative when the RPLA test was positive (13.6% for SEA, 9.0% for SEB, and 9.5% for SEC). All factors considered, the RPLA test appears most suitable for quantitatively screening large numbers of strains for staphylococcal enterotoxins.

Animals↗

Impact of proficiency testing on results of the microscopic agglutination test for diagnosis of leptospirosis.

A proficiency testing scheme for the leptospirosis microscopic agglutination test was provided to 37 laboratories in 23 countries in 2002 (round 1) and to 60 laboratories in 34 countries in 2003 (round 2). Thirty-four laboratories participated in both rounds. Each panel consisted of five rabbit serum samples, four of which were antisera raised against pathogenic serovars of Leptospira. One of these samples was a mixture of two different antisera. The rates of false-negative results, calculated on the basis of the assumption that serovars within a serogroup will cross-react, were 11% for round 1 and 14% for round 2. There were regional differences in the rates of false-negative results. The titers reported by laboratories testing for the same sample with the same serovar varied widely. Laboratories that had previously participated in round 1 reported fewer false-negative results in round 2 than new participants (10 and 21%, respectively [P = 0.002]) and reported 0.56 false-negative results per participant, whereas new participants reported 1.23 false-negative results per participant (P = 0.041). Laboratories that had previously participated also reported fewer false-negative results in round 2 than in round 1 when samples common to both rounds were tested (5 and 15%, respectively [P = 0.028]). The titers reported by the new participants were, on average, lower than those reported by the laboratories that had participated previously (P = 0.019) and were significantly more variable (P = 0.001). Analysis of these results suggests a positive impact of proficiency testing on the testing performance of the participating laboratories.

Agglutination Tests↗

[Meaning of serotype Patoc (biflexa complex) for the diagnosis of leptospirosis by microscopic agglutination test (author's transl)].

Agglutination with serotype patoc (Patoc 1) was found in 72 of 125 cases of leptospirosis. Patoc-agglutination occured frequently in leptospirosis icterohaemorrhagiae, less frequently in leptospirosis grippotyphosa and rarely in leptospirosis tarassovi. 53 cases of leptospirosis were not diagnosed when using Patoc 1 as single antigen. So we cannot recommend to use serotype patoc as the sole antigen for microscopic agglutination test. We observed 1 case in which the reaction with Patoc 1 happened earlier than the reaction with the pathogen serotypes. For this reason the battery of antigens for carrying out microscopic agglutination test should include serotype patoc, too.

Agglutination Tests↗

Use of beef extract as a diluent in direct agglutination test for visceral leishmaniasis.

Direct Agglutination Tests (DAT) have been developed for sero-diagnosis of visceral leishmaniasis (VL). The objective of this study was to find a more suitable diluent for serum dilution in a Direct Agglutination Test. 1% of beef extract (BEX) was used as a diluent in the Direct Agglutination Test; 1% foetal bovine serum (FBS) and 0.2% gelatine (Gel) were included for comparison as alternative diluents. Serum from VL patients, individuals suffering from hydatidosis, syphilis and from healthy adult Kenyans was used as control. Beef extract was found to be easy to handle, less expensive and results comparable to those obtained from the other diluents.

Agglutination Tests↗

Rapid detection of contagious bovine pleuropneumonia by a Mycoplasma mycoides subsp. mycoides SC capsular polysaccharide-specific antigen detection latex agglutination test.

A latex agglutination test (LAT) has been developed for the diagnosis of contagious bovine pleuropneumonia (CBPP). The latex microspheres were coated with MmmSC polyclonal immunoglobulin G antiserum and detected MmmSC antigen in the serum of cattle infected with CBPP and in growth medium containing MmmSC. The specific antigen recognized by this test appeared to be the capsular polysaccharide (CPS). The LAT recognized all 23 strains of MmmSC examined in this study, with a sensitivity level of 2 ng of CPS, or the equivalent of 5 x 10(3) CFU, in a reaction volume of 0.03 ml. Therefore, rapid identification of MmmSC cultures should be possible. Agglutination was also observed with the related goat pathogens and "Mycoplasma mycoides" cluster members Mycoplasma mycoides subsp. mycoides large colony biotype (four of six strains positive) and Mycoplasma mycoides subsp. capri (three of six strains positive), in agreement with the suggestion that these latter two mycoplasmas may in fact represent a single species (although collectively exhibiting two capsular serotypes). Comparisons in diagnosis with the complement fixation test (CFT) were made by using African field sera from CBPP-infected cattle. After 2 (or 3) min of incubation, the test detected 55% (or 61%) of CFT-positive sera and 29% (or 40%) of CFT-negative sera, with an overall correlation in diagnosis of 62% (or 61%). The rates for false-positive diagnoses made by using "known" CBPP-negative sera from the United Kingdom were 3 or 13% after 2 or 3 min of incubation, respectively. The data agree with previous findings that some CBPP CFT-negative misdiagnoses may occur due to "antibody eclipsing" by excess circulating antigen. The LAT combines low cost and high specificity with ease of application in the field, without the need for any specialist training or equipment.

Animals↗

Rapid detection of methicillin resistance in Staphylococcus aureus isolates by the MRSA-screen latex agglutination test.

The slide agglutination test MRSA-Screen (Denka Seiken Co., Niigata, Japan) was compared with the mecA PCR ("gold standard") for the detection of methicillin resistance in Staphylococcus aureus. The MRSA-Screen test detected the penicillin-binding protein 2a (PBP2a) antigen in 87 of 90 genetically diverse methicillin-resistant S. aureus (MRSA) stock culture strains, leading to a sensitivity of 97%. The three discrepant MRSA strains displayed positive results only after induction of the mecA gene by exposure to methicillin. Both mecA PCR and MRSA-Screen displayed negative results among the methicillin-susceptible S. aureus strains (n = 106), as well as for Micrococcus spp. (n = 10), members of the family Enterobacteriaceae (n = 10), Streptococcus pneumoniae (n = 10), and Enterococcus spp. (n = 10) (specificity = 100%). Producing the same PBP2a antigen, all 10 methicillin-resistant Staphylococcus epidermidis strains score positived in both the latex test and the mecA PCR. Consequently, the MRSA-Screen test should be applied only after identification of the MRSA strain to the species level to rule out coagulase-negative staphylococci. In conclusion, due to excellent specificity and sensitivity the MRSA-Screen latex test has the potential to be successfully used for routine applications in the microbiology laboratory.

Latex Fixation Tests↗

IgG anti-gamma-globulin factor in rheumatoid arthritis sera detected by mixed agglutination test.

In mixed agglutination tests with patient's sera and sensitized sheep erythrocytes on a glass slide, IgG rheumatoid factor was dected in 15 of 30 rheumatoid arthritis, 3 of 4 progressive systemic sclerosis and 1 of 3 systemic lupus erythematosus sera as well as in 3 of 4 synovial fluids of rheumatoid patients but in none of 10 normal sera. The IgG nature of this factor was confirmed by demonstrating this factor in IgG fractions of positive sera eluted from DEAE-cellulose and its insensitivity to mercaptoethanol.

Arthritis, Rheumatoid↗

A microtitration agglutination test for detecting group E streptococcus infection in swine.

A microtitration agglutination test was developed and evaluated for detecting infection of swine with group E streptococci type IV, the most common causative agent of streptococcic lymphadenitis of swine. Whole cell agglutinogens representing group and type antigens of group E streptococci were tested in the microtitration agglutination test against reference antisera to Streptococcus groups A, B, C, D, E, F, G. H, K, L, M, N, O, P, Q, R, S and U, as well as specific antisera to types II, IV and V of group E. Group E specific agglutinogens were unsatisfactory in the microtitration agglutination test because of cross reactions with group P and U antisera and because of poor reproducibility of the test. Type specific agglutinogens of group E streptococci reacted only with their respective homologous antisera and not with any heterologous group antisera. None of the group E streptococci agglutinogens reacted with 52 normal swine sera. Agglutinogen made from group E streptococci type IV was selected for further evaluation in the microtitration agglutination test because group E streptococci types II and V are considered to be of minor importance in the etiology of streptococcic lymphadenitis of swine. Swine experimentally infected with a type IV strain developed significant titers in the microtitration agglutination test. All swine tested negative before exposure and seroconverted (titer >/=4) two to six weeks postexposure.The microtitration agglutination test was used by two different laboratories to test 187 duplicate samples of serum from infected swine. A total of 94.1% of the tests were read at either the same titer (48.1%) or a difference of not more than one dilution (46.0%) at the two laboratories. There was disagreement between the two laboratories in the test-positive test-negative status of 19 of the sera (10.2%). Titers of two of the sera differed by two dilutions (<4 at one laboratory and 8 at the other). The remaining 17 sera differed in titer by only one dilution (<4 at one laboratory and 4 at the other).

Agglutination Tests↗

[Comparative evaluation of a latex agglutination test, two Elisa tests and a Western blot test for the serodiagnosis of human trichinellosis].

Serology is a helpful test for the diagnosis of human trichinellosis because clinical signs of this disease (fever and myalgias) are non specific. A lot of techniques have been studied but very few are commercialized and have been comparatively evaluated. We report here the performances of 4 commercially available kits: two Elisa tests, one western blot test & one latex agglutination test. The specificity and sensitivity of the different tests were assayed on 60 sera from patients with a proven trichinellosis and on 70 controls. The four tests had a 100% sensitivity. The specificity was of 98.6% for the western blot, of 93% for the latex agglutination test and of 87 & 77% for the two Elisa tests. Cross reactions are mainly observed in patients with other helminthic infections.

Blotting, Western↗

Use of the Pastorex aspergillus antigen latex agglutination test for the diagnosis of invasive aspergillosis.

AIMS: To evaluate the Pastorex aspergillus antigen latex agglutination test for the diagnosis of invasive aspergillosis in patients undergoing liver or bone marrow transplantation. METHODS: Serum samples were taken at least twice weekly post-transplant and tested for Aspergillus antigen. Latex agglutination test results were compared with microbiological examination of respiratory, urine and bile specimens. Serum samples from liver transplant patients were also tested for antibodies to Aspergillus fumigatus by counter immunoelectrophoresis. RESULTS: Eight of the 91 patients studied developed invasive aspergillosis. Positive latex agglutination tests were obtained in eight of 187 (4.3%) serum samples from four of these eight patients. The other four patients with invasive aspergillosis gave consistently negative latex agglutination tests. A positive latex agglutination test was the first indication of invasive aspergillosis in two patients; these patients were already on amphotericin B. Positive latex agglutination tests were the only evidence of invasive aspergillosis in one patient who subsequently died of the infection. False positive latex agglutination tests were obtained in five of 83 (6%) patients with no evidence of invasive aspergillosis and misleading positive cultures seen in nine of 83 (10.8%). No antibodies were detected in three of four liver transplant patients with invasive aspergillosis. Conversely, antibodies were detected in 63 of 262 (24%) serum samples from 43 liver transplant patients with no evidence of invasive aspergillosis; one of these patients had an antibody titre of 1:2 on four separate occasions. CONCLUSIONS: The Pastorex aspergillus antigen latex agglutination test, when used alone, lacks sensitivity and specificity for the early diagnosis of invasive aspergillosis. A diagnosis was made in all patients with invasive aspergillosis when both culture and antigen tests were performed although using these criteria a false positive diagnosis would have been made in 13 of 83 (15.6%) patients. Microbiological and serial serological investigations for antigen should both be performed and the results considered in conjunction with radiological and clinical evidence.

Aspergillosis↗

Identification of 22 Legionella species and 33 serogroups with the slide agglutination test.

We used the slide agglutination test to determine the serologic relationships of 22 Legionella spp. representing 33 serogroups. Antisera prepared against 14 of the Legionella spp. contained cross-reactive antibodies (1+ or greater) at their working dilutions. Numerous cross-reactions were observed for the blue-white fluorescing Legionella spp. With only three exceptions in the latter group, cross-reactive antibodies were removed by absorption, thereby producing serogroup-specific antisera. For screening tests or for identification only to the genus level, nine polyvalent antiserum pools were prepared. Routine use of slide agglutination test reagents should expand the number of Legionella spp. that can be identified in the clinical laboratory and, at the same time, provide a simpler, less costly test procedure.

Agglutination Tests↗

Detection of porcine rotavirus in stools by a latex agglutination test.

We developed a simple agglutination test for the detection of porcine rotavirus in stools from pigs with diarrhea. The virus was detected with high sensitivity and specificity by a slide agglutination test using latex particles coated with antibody against the porcine rotavirus strain OSU (LA-antiOSU). The agglutination of LA-antiOSU with OSU on a glass slide was evident macroscopically within 2 min. The sensitivity of this latex agglutination (LA) test was four times higher than that of the electron microscope method. The LA test is available for the rapid diagnosis of porcine rotavirus infections.

Animals↗

Direct agglutination test and other assays for measuring antibodies to Toxoplasma gondii.

The performance of a direct agglutination test for the detection of toxoplasma specific IgG immunoglobulin was compared with that of the latex agglutination test. The direct agglutination test was less sensitive but more specific than the latex agglutination test. Quantitative results were not directly comparable, reflecting the different antibody profiles detected in each assay. The direct agglutination test represents an alternative to the latex agglutination test as a screening test for toxoplasmosis. Patients at risk of life threatening infection require detailed serological examination using additional assays.

Agglutination Tests↗

Direct agglutination test for serologic diagnosis of Neospora caninum infection.

A direct agglutination test was evaluated for the detection and quantitation of IgG antibodies to Neospora caninum in both experimental and natural infections in various animal species. As compared with results obtained by the indirect fluorescent antibody test, the direct agglutination test appeared reliable for the serologic diagnosis of neosporosis in a variety of animal species. The direct agglutination test should provide easily available and inexpensive tools for serologic testing for antibodies to N. caninum in many host species.

Abortion, Veterinary↗

Improving agglutination tests by working in microfluidic channels.

Latex agglutination tests are used for the diagnosis of diseases in man and animals. They are generally simple, cheap, and do not require sophisticated equipment, nor highly specialized skills. In this Technical Note, we put latex agglutination tests in a microfluidic format. The experiment is performed in PDMS (polydimethylsiloxane) microchannels, using streptavidin-coated superparamagnetic beads and a magnetic field. The target molecule is biotinylated protein A. By taking full advantage of the microfluidic conditions (scaling down of the detection volume and controlled action of the shear flow), we achieved an analytical sensitivity of 10 fmol l(-1)(several hundreds of fg ml(-1)) and a fast response (a few minutes) ; the test is also quantitative. Performances of agglutination tests can thus be improved by orders of magnitude by adapting them to a microfluidic format; this comes in addition to the usual advantages offered by this technology (integration, high throughput etc.).

Agglutination Tests↗

Antibodies to spermatozoa. XII. The critical performance of the Gelatin Agglutination Test (GAT).

The Gelatin Agglutination Test for detection of sperm antibodies was critically studied and evaluated. This fundamental technique for the detection of sperm antibodies was now modified in a number of details. The new procedure, termed GAT-II, is more convenient, economical, and reliable than the older form of this procedure; the volumes used are half as much, thus using less serum and less antigen, the mixtures are prepared within each Kibrick tube, thus requiring fewer transfer steps, and the foam problem is prevented, thus making observation more accurate. Secondly, an extensive study was made of the effect of the time of incubation in this procedure, comparing 30, 60, and 120 minutes for each test mixture. It was found that only 7 of the 50 tested sera (14%) showed a positive result at 30 minutes, although all 50 were positive at 120 minutes. Various details of this sort must be carefully considered, in order to make this test fulfill its potential and have maximum reliability for clinical significance.

Agglutination Tests↗