Influence of ionizing radiation on the antimicrobial activity of the antibiotics sulfamethoxazole and trimethoprim.

The response of the antimicrobial compounds sulfamethoxazole (SMX) and trimethoprim (TMP) - individually and in mixtures - to ionizing radiation was investigated using laboratory prepared mixtures and a commercial pharmaceutical formulation. The residual antibacterial activity of the solutions was monitored using Staphylococcus aureus and Escherichia coli test strains. Based on antibacterial activity, SMX was more susceptible to ionizing radiation as compared to TMP. The antibacterial activity of SMX and TMP was completely eliminated at 0.2 kGy and 0.8 kGy, respectively. However, when SMX and TMP were in a mixture, the dose required to eliminate the antibacterial activity was 10 kGy, implying a synergistic antibacterial activity when these are present in mixtures. Only when the antibiotic concentration was below the Minimum Inhibitory Concentration of TMP (i.e., 2 µmol dm-3) did the antibacterial activity of the SMX and TMP mixture disappear. These results imply that the synergistic antimicrobial activity of antimicrobial compounds in pharmaceutical waste streams is a strong possibility. Therefore, antimicrobial activity assays should be included when evaluating the use of ionizing radiation technology for the remediation of pharmaceutical or municipal waste streams.

Preliminary study for evaluation of avian influenza virus inactivation in contaminated poultry products using electron beam irradiation.

Spread of avian influenza is associated with movement of infected poultry and poultry products, and, as a result, strict international trade restrictions are in place. In addition, the possibility of transmission of avian influenza virus (AIV) strains to mammalian species by the consumption or handling of infected poultry, although a rare occurrence, is an important trade concern. Traditional methods for poultry product decontamination, such as thermal processing, are effective in inactivating AIV. However, alternative technologies such as electron beam (E-beam) irradiation offer some advantages in maintaining organoleptic properties of fresh poultry products. This study was designed to evaluate the applicability of high-energy (10 MeV) E-beam irradiation to inactivate AIV and reduce virus loads in egg products and poultry meat. Commercially available egg-white and ground turkey meat samples were spiked with the low-pathogenic A/chicken/TX/2002 H5N3 AIV and exposed to varying doses of high-energy E-beam irradiation in increments ranging from 0 kGy to 8 kGy. The viral titres in irradiated samples showed a linear dose-dependent reduction. The dose required to achieve 90% reduction (i.e. the D (10) value) of viable AIV loads was 2.3 kGy in phosphate buffer, 1.6 kGy in egg-white and 2.6 kGy in ground turkey meat samples. The effectiveness of E-beam irradiation to inactivate AIV was similar to the previously reported effectiveness of the E-beam against poliovirus and rotavirus. These results illustrate the potential applicability of high-energy (10 MeV) E-beam irradiation as a poultry product decontamination technology to inactivate AIV.

A rapid viability assay for Cryptosporidium oocysts and Giardia cysts for use in conjunction with indirect fluorescent antibody detection.

There is an urgent need to develop rapid methods to determine the viability of Cryptosporidium oocysts and Giardia cysts in environmental samples, especially water. The inclusion of the vital dye propidium iodide (PI) by oocysts and cysts has been previously shown to correlate well with nonviability. The ability of nonviable oocysts and cysts to include PI has been employed to develop a rapid viability determination method that could be used in conjunction with the current indirect fluorescent antibody (IFA) method for detecting oocysts and cysts. The efficacy of this PI-IFA method to detect and determine the viability status of oocysts/cysts has been tested using oocyst samples inactivated by three different approaches. The ability to incorporate PI staining with IFA detection provides the advantage of both detection and viability determination at the same time, using the same sample.