Quantitative determination of recombinant bovine somatotropin in commercial shrimp feed using a competitive enzyme-linked immunosorbent assay.

Recombinant bovine somatotropin (rbST), also known as growth hormone, is used to enhance production and development of animals within the agriculture and aquaculture industries. Its use is controversial because of its potential effects on human and animal health. To screen for rbST in shrimp feed, a competitive enzyme-linked immunosorbent assay (ELISA) with an inhibition step was developed. Sample and rbST antibody (rabbit anti-rbST) were incubated at room temperature for 30 min. Subsequently, this competitive reaction was transferred to a microplate coated with rbST, using goat antirabbit IgG linked with horseradish peroxidise as the secondary antibody. Substrates for peroxidise were added, and the absorbance at 410 nm was determined. The applicability of the method was assessed using rbST extracted from "spiked" shrimp feed samples. The assay was reproducible and linear with R(2) values greater than 0.98 over the standard curve range of 20-500 microg/g. The intra- and interday precisions expressed as relative standard deviations were 3.4 and 5.3%, respectively. The mean recovery from 15 spiked feed samples was 105%. This assay will be a valuable tool for quantitative detection of rbST by both governments and commercial companies and can be modified for other types of feed.

Seroreactivity against streptococcal DRS (distantly related to SIC) protein is a predictor for end-stage renal failure.

We hypothesized that immunoreactivity against antigens from nephritic strains of Streptococcus pyogenes may be elevated in patients with end-stage renal failure (ESRF). Additionally, we investigated whether a difference in seroreactivity exists between nonindigenous and indigenous (Aboriginal/Torres Strait Islander) patients. To examine these possibilities, antibodies against potentially nephritogenic proteins, streptokinase (Ska1) (from M1), streptococcal pyrogenic exotoxin type B (SpeB) (from M1), the streptococcal inhibitor of complement-mediated cell lysis (SIC) (from M1) and its two variants, closely related to SIC (CRS) (from M57) and distantly related to SIC (DRS) (from M12) were determined in 66 patients and 31 healthy controls by enzyme-linked immunosorbent assays. A significantly higher proportion of patients compared to controls were seropositive to Ska1 (P = 0.004), DRS (P = 0.0003), CRS (P = 0.001), and SIC (P = 0.018). Regression analysis showed that seroreactivity to DRS (r(2) = 0.85, P = 0.001) predicted the development of ESRF and that being diabetic was positively associated with being an ESRF patient (r(2) = 0.37, P < 0.0001) and being indigenous (r(2) = 0.47, P < 0.0001). These results suggest that these ESRF patients were exposed to strains of S. pyogenes that secrete Ska1, DRS, CRS, and SIC and may have pathological significance. No significant difference was observed between the indigenous patients and nonindigenous patients.