Detection of immunoglobulin G (IgG) and IgM antibodies to Toxoplasma gondii: evaluation of four commercial immunoassay systems.

A comparative evaluation of the following commercial immunoassays for the determination of antibodies to Toxoplasma gondii was performed: Behring Diagnostics OPUS Toxo G and Toxo M, Abbott Diagnostics IMX Toxo-IgG 2.0 and Toxo-IgM, Sanofi Diagnostics Pasteur Platelia Toxo IgG and Toxo IgM, and bioMérieux Vitek VIDAS Toxo IgG and IgM. Of 676 specimens that were tested for Toxoplasma-specific immunoglobulin G (IgG) antibodies, 26% were reactive by all methods while 8% displayed some discrepancy. Of 718 specimens that were tested for Toxoplasma-specific IgM antibodies, 3% were reactive by all methods while 10% displayed some discrepancy. Analysis of discrepant specimens revealed performance shortcomings with all IgM-specific assays. The impact of such shortcomings is magnified in a population with a low prevalence of toxoplasmosis.

Helicobacter pylori--in vitro susceptibility to garlic (Allium sativum) extract.

Gastric cancer is the major cancer in the developing world and one of the top two worldwide. Helicobacter pylori is a bacterium implicated in the etiology of stomach cancer. The incidence of stomach cancer is lower in individuals and populations with high Allium vegetable intakes. Allium vegetables, particularly garlic, have antibiotic activity. Standard antibiotic regimens against H. pylori are frequently ineffective in high-risk populations. As part of our study of the role of Allium vegetable intake on cancer prevention, we wished to investigate its antimicrobial activity against H. pylori. An aqueous extract of garlic cloves was standardized for its thiosulfinate concentration and tested for its antimicrobial activity on H. pylori grown on chocolate agar plates. Minimum inhibitory concentration was 40 micrograms thiosulfinate per milliliter. Staphylococcus aureus tested under the same conditions was not susceptible to garlic extract up to the maximum thiosulfinate concentration tested (160 micrograms/ml). To our knowledge, this is the first report of H. pylori's susceptibility to garlic extract of known thiosulfinate concentration. It is plausible that the sensitivity of H. pylori to garlic extract at such low concentration may be related to the reported lower risk of stomach cancer in those with a high Allium vegetable intake. Furthermore, it may identify a strategy for a low-cost intervention, with few side effects, in populations at high risk for stomach cancer, particularly where antibiotic resistance and the risk of reinfection are high.

Inhibition of acetylating activity in an enzymatic assay for aminoglycoside antibiotics.

The radioenzymatic technique using aminoglycoside-6'-acetyltransferase is suitable for determining serum concentrations of aminoglycoside antibiotics that have a 6'-amino group. Standard curves constructed for each drug in normal human serum are generally satisfactory, but we encountered a pool of human serum (designated IN pool) that inhibited the acetylating activity of the assay. Standard curves for amikacin, kanamycin, gentamicin, and tobramycin in the acetylating assay were all abnormal with standards prepared in the IN pool. Acetylating activity was also inhibited with amikacin standards prepared in a filtrate of this serum pool. Heat inactivation (56 degrees C for 30 min) of the IN pool did not eliminate the problem. When the IN pool was diluted 1:10 in normal human serum, the standard curve obtained with amikacin was comparable to the curve with standards prepared in normal human serum. With amikacin standards prepared in a 1:2 dilution of the IN pool in normal human serum, an intermediate level of acetylating activity was observed. When this IN pool was used for the preparation of gentamicin and amikacin standards in a bioassay with Klebsiella pneumoniae ATCC 27799 as the test strain, valid standard curves and concentrations were obtained. Furthermore, no differences in the biological activity of amikacin were observed with Pseudomonas aeruginosa or Bacillus subtilis as the test strain. Excellent agreement between the microbial assay and the enzymatic assay was obtained with serum specimens tested for gentamicin (r = 0.89), tobramycin (r = 0.96), and amikacin (r = 0.96). The results obtained with the IN pool illustrate the need for regular use of check samples of known performance, independent from the standards, when determining antibiotic levels in serum.