Use of a new rapid bioluminescence method for screening organophosphate and N-Methylcarbamate insecticides in processed baby foods.

An enzyme with high specific affinity for organophosphate and N-methylcarbamate insecticides has been incorporated into a new test for detection of these insecticides at the level of parts per billion (ppb) (commercially available as the Charm Pesticide Test). To measure the extent of insecticide inhibition of the enzyme, a specific bioluminescent substrate is used. The signal is counterproportional to the amount of insecticides. Random sampling of four baby food brands and testing for the cumulative levels of organophosphate and N-methylcarbamate insecticides found carbaryl to be the most common residue. Out of the 155 samples tested there were 132 negative samples (85.2%) and 23 suspected positive samples (14.2%). The suspected positive samples were further analyzed by high-performance liquid chromatography (HPLC) and gas chromatography/mass spectrometry (GC/MS). Carbaryl was confirmed in 18 of the samples. One of the samples contained an active metabolite of tetrachlorvinphos and in 3 of the positive samples an insecticide could not be identified by GC/MS. One positive sample was not processed for confirmation due to high fat content.

High-temperature short-time heat inactivation of HIV and other viruses in human blood plasma.

An ultra-short-time heating system was used to process blood plasma spiked with various viruses (HIV, vesicular stomatitis virus, encephalomyocarditis virus). Virus reduction and recovery of plasma proteins were measured at various temperatures from 65 to 85 degrees C. Processing at 77 degrees C and 0.006 s resulted in a high level of virus kill, including greater than or equal to 4.4 log10 HIV, while maintaining protein structure and activity essentially intact.

Microbial receptor assay for rapid detection and identification of seven families of antimicrobial drugs in milk: collaborative study.

A microbial competitive receptor assay for detecting residues of antibiotic families in milk was studied collaboratively by 13 laboratories. The drugs and levels (ppb) tested in this study include penicillin G, 4.8; cephapirin, 5.0; cloxacillin, 100; tetracycline, 2000; chlortetracycline, 2000; oxytetracycline, 2000; erythromycin, 200; lincomycin, 400; clindamycin, 400; sulfamethazine, 75; sulfamethoxazole, 50; sulfisoxazole, 50; streptomycin, 1000; novobiocin, 50; and chloramphenicol, 800. In this method, microbial cells added to a milk sample provide specific binding sites for which 14C or 3H labeled drug competes with drug residues in the sample. The 14C or 3H binding to the specific binding sites is measured in a scintillation counter and compared with a zero standard milk. If the sample is statistically different from the zero standard, it is positive. The assay takes about 15 min. The binding reaction occurs between the receptor site and the drug functional group, so all members of a drug family are detected. In this case, beta-lactams, tetracyclines, macrolides, aminoglycosides, novobiocin, chloramphenicol, and sulfonamides, including p-aminobenzoic acid (PABA) and its other analogs, are detectable. The incidence of false negative determinations among samples is about 1%; the incidence of false positives is about 3%. For negative cases, the relative standard deviations for repeatability ranged from 0 to 5% and for reproducibility from 0 to 6%. For positive cases, relative standard deviations ranged from 0 to 13% for repeatability and from 0 to 14% for reproducibility. The method has been adopted official first action.

Rapid screening assay for beta-lactam antibiotics in milk: collaborative study.

A 15 min assay for beta-lactam antibiotics has been used by dairies for several years as a screening procedure for testing milk tankers before they unload. The test is based on a competition between 14C-penicillin and beta-lactam antibiotics in the milk samples for sites on a microbial cell wall that specifically binds beta-lactam. In a collaborative study, 11 laboratories correctly distinguished 10 coded zero penicillin G samples and 10 coded 0.01 IU/mL samples. The proposed test is qualitative, positive or negative, and can detect the presence of beta-lactam antibiotics at the 0.01 IU/mL level. The control point for determining positive or negative samples is more than 3 standard deviations from the mean of 0.01 IU/mL. The method has been adopted official first action.

Method for continuous purification of biological material using immunosorbent.

A mechanical device for the continuous purification of biological material using immunosorbent was developed. The system consists of heat-sealed nylon pouches containing agarose-bound antibody, attached to an endless 35 mm wide Mylar belt that passes through four chambers sequentially. The biological material is bound and dissociated, and the immobilized antibody is regenerated for repeated isolation and purification of antigen. The belt design incorporates features to minimize carry-over between chambers and prevent damage to the agarose-bound antibody in repeated passes through the system. An existing batch method for the purification of human placental alkaline phosphatase using immobilized rabbit antisera was adapted to continuous purification in the device. The belt contained a low affinity immunosorbent and made five complete passes through the system. A decrease in antigen binding capacity between free immunosorbent suspensions and belt immunosorbent in pouches was observed. This was shown to be the result of the diffusion resistance offered by the pouch and the short exposure times of each pouch in the chambers. A decrease in antigen binding capacity between successive belt passes was also observed, and resulted from the inability of the agarose in the pouches to resuspend completely after each pass. The low efficiency of the agitation method and the roller device used to squeeze the pouches were the reasons for this deficiency.

The derivatization of oxidized polysaccharides for protein immobilization and affinity chromatography.

The present report describes the preparation of modified polysaccharides matrices useful for the synthesis of affinity adsorbents and immobilized proteins. Hydrazido-matrices were synthesized by condensing an excess of the bifunctional reagent, adipic acid dihydrazide, with periodate oxidized cellulose paper, Sephadex, or Sepharose matrices. Ribonucleotide dialdehyde cofactors, glyceraldehyde 3-phosphate, pyridoxal 5'-phosphate and oxidized DNAase B were separately bound to the hydrazido-polymers. Azido-matrices obtained by modification of the hydrazido-derivatives were coupled to specific amino ligands such as amino acids and proteins. Several adsorbents were prepared and used as models for affinity chromatography.