Polymacron enzyme immunoassay system for detection of naturally contaminating Salmonella in foods, feeds, and environmental samples

A simple dot blot enzyme immunoassay was developed to screen enrichment broth cultures for the presence of Salmonella. This unique system utilizes macroporous polyester cloth (Polymacron) with an inexpensive hemoglobin coating to provide a high-affinity adsorbent for lipopolysaccharide (LPS) antigens in test samples. Bound LPS antigens are then detected using a monoclonal antibody conjugate recognizing a core oligosaccharide epitope common to all salmonellae frequently found in foods and related samples. The entire test (not including enrichment culture) could be completed in less than 1 h. The performance of this assay was evaluated in the analysis of enrichment broth cultures from a variety of egg and dairy products, chicken carcasses, animal feeds, and food-processing plant environmental samples for the presence of Salmonella.     

Detection of Salmonella in dry foods using refrigerated pre-enrichment and enrichment broth cultures: interlaboratory study

An interlaboratory study was performed in 11 laboratories to validate the use of pre-enrichment and tetrathionate brilliant green (TBG35) and selenite cystine (SC35) enrichment cultures refrigerated 72 h at 2-5 degrees C for greater analytical flexibility in the detection of Salmonella in dry foods. Productivities of refrigerated pre-enrichment and enrichment cultures were compared with that of the AOAC/Bacteriological Analytical Manual (BAM) procedure using 4 food types: whole egg powder, milk chocolate, animal feed, and instantized skim milk powder. Uninoculated and inoculated samples were included in each food group. There was complete agreement between the results obtained by the standard AOAC/BAM procedure and the 2 refrigeration procedures. Of 660 samples tested, the AOAC/BAM procedure identified 393 contaminated samples that were readily detected from the corresponding refrigerated pre-enrichment cultures and from the combined productivity of homologous refrigerated TBG35 and SC35 cultures. Refrigeration (72 h) of pre-enrichment or enrichment cultures for greater analytical flexibility and laboratory productivity in the examination of dry foods is under review for adoption by AOAC International.     

Detection of Salmonella in dry foods using refrigerated pre-enrichment and enrichment broth cultures: summary of collaborative study

A collaborative study was conducted to compare the productivity of refrigerated pre-enrichment and enrichment broth cultures with the U.S. Food and Drug Administration culture methods for detection of Salmonella. The refrigerated pre-enrichment and selective enrichment broth culture methods for detection of Salmonella in dry foods have been adopted first action by AOAC INTERNATIONAL.     

A collaborative study on the detection of staphylococcal enterotoxins in foods by an enzyme immunoassay kit (RIDASCREEN)

The RIDASCREEN SET kit (R-Biopharm GmbH, Darmstadt, Germany), a commercial staphylococcal enterotoxin (SE) immunoassay kit, utilizes monovalent capture antibodies against SE types A to E (SEA to SEE); therefore, it simultaneously detects and identifies the enterotoxin types. A collaborative study was conducted to ascertain whether the specificity, sensitivity, repeatability and reproducibility of the kits would meet food safety criteria. Twelve Canadian laboratories participated in this study to analyze various foods to which 1.0 to 2.0 ng of SE/g had been added and negative control samples. The results indicate that the sensitivity and specificity of the kit were excellent; all collaborators were able to detect the minimum toxin levels of 1.0 ng SEA/g in ham and cheese, 1.0 ng SEB/g in salami and turkey, and 2.0 ng SED/g in other samples without any false-negative results. With regard to negative control samples, all analysts obtained correct results except for one analyst who recorded weak false-positive results with several foods detecting SEC or SEA. The overall rate of false-positive results was 0.7% for 600 triplicate assays. In addition, it was confirmed that the RIDASCREEN kit did not yield false-positive results with mussels in contrast to some other EIA kits. Overall repeatability and reproducibility of the kit were in the range of 11.69-42.57% and 17.25-68.05%, respectively.     

Occurrence of aflatoxins, fumonisin B1, and zearalenone in foods and feeds in Botswana

Sorghum and maize form the main dietary staple foods in Botswana. Other products such as peanuts, peanut butter, phane (an edible larval stage of an emperor moth Imbrasia belina Westwood), and pulses (cowpeas and beans) are also widely used as food and for the manufacture of feeds. These important food and feed commodities were analyzed for the presence of aflatoxins, fumonisin B1, and zearalenone. Aflatoxins were detected in 40% of the samples analyzed. The concentration of total aflatoxins ranged from 0.1 to 64 microg/kg. The mean concentration ranged from 0.3 microg/kg in sorghum to 23 microg/kg in peanut butter. Peanut butter samples were the most contaminated (71%). No aflatoxins were detected in maize. Fumonisin B1 was detected in 36% of the samples. Maize samples were the most contaminated (85% of the samples) with the concentration ranging from 20 to 1,270 microg/kg. No fumonisin B1 was detected in peanuts, phane, and beans. Zearalenone was only found in 2.6% of the samples analyzed at 40 microg/kg. Aflatoxins were the most common toxins detected in foods and feeds in Botswana. However, fumonisin B1 was more prevalent in maize than aflatoxins or zearalenone.     

Evaluation of an antigen-capture enzyme immunoassay for detection of Entamoeba histolytica in stool samples

In order to identify the prevalence of Entamoeba histolytica in tourists with diarrhoea returning from countries of the developing world, sensitivity and specificity of a commercially available enzyme immunoassay (EIA) kit for the detection of Entamoeba histolytica coproantigen in stool were evaluated. Five hundred seventy-seven specimens from 469 patients were examined by microscopy and EIA. Sixty-two specimens from 49 patients were considered positive for Entamoeba histolytica. Compared with microscopic examination of stool samples, the EIA was found to be slightly more sensitive (90.3% vs. 87.1%) and was 97.7% specific for Entamoeba histolytica.     

Determination of total fat in foods and feeds by the caviezel method, based on a gas chromatographic technique

This peer-verified method specifies a fast, easy, and reliable quantitative method to determine total fat in foods and feeds in compliance with the new definition of fat from the U.S. Food and Drug Administration. The method takes into consideration all fatty acids, from C4 to C24, and when fat is present at 0.3-100%. The validation study included 9 matrixes, with fat levels ranging from 1 to 79%. Sample and internal standard (IS; tridecanoic acid) are added to solvent (n-butyl alcohol). Fat is extracted and simultaneously saponified by potassium hydroxide. The fatty acid potassium salts are converted to fatty acids by adding an acidic aqueous salt solution, which produces a 2-phase system. The upper phase, containing the fatty acids and IS, is injected into the fat determination system. After gas chromatographic separation, the fat content is calculated from IS and fatty acid peak areas. The fat content is automatically converted to triglyceride content with a pre-determined factor. Ten replicates of 9 different food samples, which cover the whole range of different contents in fat, proteins, and carbohydrates, were analyzed by the submitting and the peer laboratories. Repeatability relative standard deviation (RSDr) values ranged from 0.47 to 4.62%. Reproducibility relative standard deviation (RSDR) values ranged from 0.85 to 9.52%. These estimates include between-run variability. The method shows good accuracy. Values for standard reference materials (SRMs) are in agreement with certified values. Regression analysis of the correlation between observed fat and certified value over all matrixes and fat levels indicated good precision and absence of method bias (5 SRMs; 1-30% fat; correlation coefficient, R2 = 99.98%).     

Detection of Chlamydia trachomatis in urine samples by nucleic acid tests: comparison with culture and enzyme immunoassay of genital swab specimens

Two commercially available nucleic acid-based tests, ligase chain reaction (LCR; Abbott Laboratories) and PCR (Roche Diagnostics), for the detection of Chlamydia trachomatis in male and female urine samples were compared with culture and enzyme immunoassay (EIA) (Microtrak; Syva) for C. trachomatis detection in genital samples. The samples were collected from 1,005 patients who attended a sexually transmitted disease clinic. In this study population, the prevalence of the infection was 4%. Specimens which were reactive in any of the tests were retested with a different PCR test using primers directed against the major outer membrane protein gene. With a "gold standard" of a positive culture, or any other positive test result if it was confirmed by an independent test, the Roche PCR (95% sensitive, 99.9% specific) was more sensitive than the LCR (75% sensitive, 100% specific) (chi2, P < 0.0001) while both tests were more sensitive than culture (58% sensitive, 100% specific) or EIA (45% sensitive, 100% specific) (chi2, P < 0.001). The Roche PCR and Abbott LCR tests of urine identified 65% and 30% more positive patients, respectively, than did testing by culture of urethral or cervical specimens. Nucleic acid testing of urine specimens for C. trachomatis is a more sensitive and convenient method for the detection of genital infection.     

Assay of thiamine in foods, using manual and semiautomated fluorometric and microbiological methods

Three methods for the determination of thiamine in foods were evaluated for accuracy, recovery, and precision: a manual fluorescent method, a semiautomated fluorescent method, and a Lactobacillus viridescens microbiological assay. Thiamine in the samples was destroyed with clam tissue thiaminase; a known amount of thiamine hydrochloride was then added to the extract; and the thiamine recovery was determined. For 14 commerically processed food products analyzed by the manual and semiautomated methods, the mean per cent recovery values and standard deviations were 91.2 +/- 8.92 and 99.3 +/- 3.13%, respectively. Eight of these products were analyzed by all 3 methods. The mean per cent recoveries and standard deviations for these 8 samples were 90.7 +/- 8.97, 101 +/- 2.52, and 99.9 +/- 1.03%, respectively, for the manual, semiautomated, and microbiological methods. The microbiological method with L. viridescens gave the best results for the products tested. The concentration of vitamin which can be measured is such that samples of low label declaration present no problems. The semiautomated method offers a rapid and accurate method of thiamine assay. The chemical reactions are identical to those of the official method. The major difference between the methods is in the sample cleanup. It is postulated that the low recovery observed for the manual method is due to incomplete elution of thiamine in the column purification step.     

Detection of Helicobacter pylori in stool specimens by PCR and antigen enzyme immunoassay

A highly sensitive seminested PCR assay to detect Helicobacter pylori DNA in feces was developed. PCR with stool specimens and a novel antigen enzyme immunoassay (EIA) for H. pylori detection in feces were evaluated as diagnostic tools and in follow-up with samples from 63 infected and 37 noninfected persons. Infected individuals received eradication therapy followed by endoscopic follow-up 35 days after the start of treatment. At that time, a second stool specimen was obtained from 55 of these patients. Before eradication, the sensitivity of PCR was 93.7% and that of EIA 88.9%. Specificities were 100 and 94.6%, respectively. Of the 55 follow-up specimens, 41 originated from patients from whom H. pylori had been eradicated. Of these, 21 were still positive by PCR and 13 were positive by EIA, indicating that 1 month may be too short a period for follow-up evaluation of stool specimens by these tests.     

共沉淀富集分离-ICP—MS法测定地球化学勘探样品中的超痕量金、铂、钯

建立了碲作为共沉淀剂分离富集,采用ICP—MS测定地球化学勘探样品中超痕量金、铂、钯的方法,并研究了共沉淀时各种因素的影响;确定了采用盐酸和氯酸钾分解试样,以2mg碲对金、铂、钯进行共沉淀分离富集,抽滤,残渣用王水溶解,采用电感耦合等离子体质谱法测定的条件。该方法检出限分别为：Au0．062ng／g、Pt0．041ng／g、Pd0．043ng／g,相对标准偏差（n=12）：Au4．81％、R5．46％、Pd3．50％。采用该方法测定了国家一级地球化学标准物质中的痕量Au,Pt,Pd,测定值与标准值相符合。     

Interaction of environmental enrichment and genotype.

Assessed the effects of exposure to an enriched environment, from birth-38 days of age, using 3 behavioral tests: open field, exploration, and running wheels. 144 inbred mice from 3 strains (A/J, C3H/HeJ, and C57BL/10J) were used as Ss in a 3 * 2 * 2 factorial design: 3 strains, enriched and control treatment, and males and females. Significant main effects due to strain, treatment, and trials were found in open-field activity, exploration, and running-wheel activity. Main effects due to strain and trials were found in open-field defecation. Genotype interacted with treatment on 3 of the 5 dependent measures and interacted with trials on all measures. Coefficients of genetic determination for the various dependent measures were between .08 and .43. Results support the hypothesis that environmental enrichment increased activity and decreased exploration. (28 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Predominant serovars of Salmonella in humans and foods from Thailand

During the period from 1993 to 1996, a total of 27,497 Salmonella isolates from humans, chicken meat, ready-to-eat Thai foods and shrimps were serotyped to know the predominant serovars of Salmonella in humans and foods in Thailand. Seventy-two and 81 serovars of Salmonella were identified in human and food samples, respectively. The significance of foods as a vehicle for human salmonellosis was discussed from an epidemiological viewpoint.     

Quantitative determination of serum anti ribosomal-P protein antibody by enzyme immunoassay

An enzyme immunoassay for serum anti-ribosomal P protein antibodies (anti-P) is developed, using highly purified synthetic ribosomal P peptides of the carboxyl terminal 22 amino acid sequence conjugated to human serum albumin (HSA) as an antigen. Anti-P levels were determined by subtracting the nonspecific binding activities to HSA. The concentration of anti-P which produced half of the maximal absorbance at 492 nm (OD492) given by saturating concentrations of anti-P in the ELISA plate was defined as 1 U/ml. The anti-P values in the samples were determined by referring to a standard curve made from a standard serum containing anti-P. Serum anti-P levels in 34 normal individuals were 5.52 +/- 8.39 U/ml (mean +/- SD). Anti-P in sera from 45 patients with systemic lupus erythematosus (SLE), 24 patients with rheumatoid arthritis (RA) and 27 patients with Beh?et's disease were also analyzed. The values for serum anti-P in SLE, RA and Beh?et's disease groups were 251.04 +/- 843.07 U/ml, 5.97 +/- 15.18 U/ml, and 2.62 +/- 3.35 U/ml (mean +/- SD) respectively. The positive ratio for serum anti-P in SLE patients was significantly higher than that in patients with RA or Beh?et's disease (p < 0.05 as determined by chi-square test). These results indicate that quantitative determination of serum anti-P by our enzyme immunoassay is a successful tool for the diagnosis of SLE.     

Assay of 222Rn in water samples by a modified integral counting method

22Rn activity concentrations in water collected from 163 private wells and 14 springs in Tokyo were measured with a liquid scintillation spectrometer using a modified integral counting method. The activity concentrations of 222Rn range from 0.2 to 22.9 Bq/L and average 4.8 Bq/L. The errors due to the air luminescence counts and the interferences from 220Rn and 219Rn are discussed and evaluated. 222Rn samples of 0.2 Bq/L can be assayed within an overall uncertainty of 3.1%. The liquid scintillation method involving agitation of the sample water directly with a liquid scintillation cocktail was compared with the present method and evaluated.     

Determination of cereal herbicide residues in environmental samples by gas chromatography

Gas chromatographic analysis of cereal herbicide residues in water, soil, plant and air is reviewed. Herbicides widely used in spring and winter cereals, i.e., phenoxyacids, benzonitriles, ureas, triazines, dinitroanilines, chloroacetamides and thiocarbamates, are considered. The main procedures used in the residue analysis, extraction, clean-up, derivatization and gas chromatographic determination are summarized and discussed.     

Sensitivity of microscopy versus enzyme immunoassay in the laboratory diagnosis of giardiasis

The substitution of enzyme immunoassay (EIA) techniques for microscopy as a screening tool for Giardia lamblia infection was assessed. Paired stool samples obtained within a ten-day period from 366 patients with persistent diarrhea were examined by microscopy. In addition, two commercially available Giardia lamblia-specific EIAs were performed. Compared with microscopy, EIA for copro-antigen detection was more sensitive, based on examination of either one or two stool samples. Repeated examinations increased the number of cases detected, more so for microscopy than EIA. The negative predictive values of the two EIAs performed on the first stool sample were 98.7% and 97.8%. The results show that EIA for detection of copro-antigens in a single stool sample may be almost as sensitive for identifying Giardia infection as repeated microscopy on two sequential stool samples.     

Recombinant mono- and polyantigens to detect cytomegalovirus-specific immunoglobulin M in human sera by enzyme immunoassay

Serological detection of human cytomegalovirus (HCMV)-specific antibody varies greatly because of antigen composition and the lack of antigen standardization. Antigenic materials composed of single well-characterized viral proteins or portions of them, produced via molecular biology, have proven to be promising tools in improving serodiagnosis. We constructed a recombinant protein containing two regions of ppUL32 (p150) and half of ppUL44 (p52) and compared the immunoglobulin M (IgM) reactivity of this triple-antigen fusion protein with that of a double-antigen fusion protein containing the two ppUL32 fragments and that of a monoantigen fusion protein containing half of ppUL44. We also constructed and tested two other monoantigen fusion proteins containing a large fraction of ppUL80a and a fraction of ppUL83. More than 700 serum samples from different groups of immunocompetent and immunosuppressed subjects were tested for the presence of HCMV IgM by recombinant enzyme immunoassay (rec-EIA) and by a commercially available EIA. Western blotting (immunoblotting) and (in the case of immunosuppressed individuals) antigenemia tests by immunofluorescence and PCR of polymorphonuclear leukocytes were also carried out. The results obtained demonstrate that (i) the triple-antigen fusion protein can replace the individual proteins; (ii) the triple-antigen fusion protein cannot be used alone to replace the virus or infected cells in the serological detection of anti-CMV IgM; (iii) the addition of the fusion proteins containing portions of ppUL83 and ppUL80a is essential for the formation of an antigenic mixture that can replace the virus for the search of HCMV-specific IgM; (iv) rec-EIA is very specific and is more sensitive than the commercially available EIA, and the results obtained are consistent with those obtained by Western blotting; and (v) rec-EIA can reliably be used to detect HCMV-specific IgM in different groups of patients with active HCMV infection.     

巯基葡聚糖凝胶分离富集—氢化物发生原子荧光法测定地球化学样品中锑

建立了采用巯基葡聚糖凝胶分离富集,氢化物发生原子荧光法测定地球化学样品中锑的方法。以微波消解分解样品,缩短了样品处理时间,避免了挥发组分的损失。经巯基葡聚糖凝胶吸附柱分离富集锑,用6.0 mol/L HCl洗脱,氢化物发生原子荧光法测定。通过试验确定了仪器最佳工作条件,吸附和洗脱条件,氢化物发生最佳条件及微波消解程序,并对共存干扰元素的允许量进行了研究。在此条件下测定锑,得出该方法的检出限为0.25μg/L,线性范围0.001～0.20 mg/L,相对标准偏差(n=6)为2.9%～5.1%,加标回收率99     

Epidemiological studies on Salmonella in a certain area ("Walcheren project"). I. The presence of Salmonella in man, pigs, insects, seagulls and in foods and effluents

During a certain period various materials (pigs, foods, insects, seagull droppings, chopping-block scrapings from butcher's shops, effluents of sewage treatment plants and stools of patients) were examined for the presence of Salmonella at the same time in a relatively small area (Walcheren). Certain types of Salmonella (S. typhi murium type II 505, S. panama, S. infantis and S. brandenburg) were frequently isolated from almost all materials examined. This may indicate the existence of Salmonella contamination cycles: one may think of the cycle: slaughter animal (infected from the environment and/or by meal) - meat - consumer - patient or healthy carrier - effluent and surface water - insects, birds and rodents - slaughter animal or meat and possibly other foods - consumer.