ABSTRACT
A modification of the Blood Products Laboratory radioimmunoassay for hepatitis B surface antigen which allows simultaneous assay of both hepatitis B surface antigen and antibody is described. The sensitivity of the method has been assessed and its performance as a screening test in over 2,500 routine samples has been evaluated.
Subject(s)
Hepatitis B Antibodies/analysis , Hepatitis B Surface Antigens/analysis , Evaluation Studies as Topic , Hemagglutination Inhibition Tests , Hemagglutination Tests , Humans , Radioimmunoassay , Reagent Kits, DiagnosticABSTRACT
AIMS: To provide data on the survival of Cryptosporidium oocysts in a range of conditions relevant to foods and beverages. METHODS AND RESULTS: Cryptosporidium parvum and C. hominis oocysts were stored in buffered media at different pH values and with various acids. In addition, neutral solutions with high salt (4.5% w/v), glycerol (20% v/v), sucrose (50% w/v) or ethanol (9 and 40% v/v) were used to determine their effects on survival. After storage periods of between 1 h and 14 days, viability was assessed using sporozoite ratio or infection of MRC-5 cell monolayers (not previously reported for culture of this organism). With all treatments, and with both assay techniques, viable oocysts were found at the end of the storage periods. However, treatments with one of the following additions: high salt, glycerol, sucrose or ethanol showed a negative and statistically significant effect on survival. Decline was noted after 1 day or even 1 h of treatment. CONCLUSIONS: MRC-5 cells are suitable for infection by C. parvum and C. hominis. Both tissue culture and sporozoite ratio gave broadly similar survival results and the greatest effects were seen with addition of components which reduced water activity. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has provided useful additional information to the food industry when considering the risk posed by this organism.