Susceptibility of human rotavirus to ozone, high pressure, and pulsed electric field.

The rotavirus causes a food-transmitted gastroenteritis that affects mainly children. Currently, the food industry is interested in alternative food-processing technologies, but research on the control of food-transmitted viruses by these technologies is limited. In this study, the human rotavirus was cultured on MA104 cells, and suspensions of the virus were prepared and treated with ozone, high pressure, and pulsed electric field (PEF). Virus viability was quantified as 50% tissue culture infectious doses (TCID50) per milliliter. Ozone at 25 microg/ml decreased rotavirus infectivity by 8 to 9 log10 TCID50/ml. High pressure was extremely effective against the rotavirus; treatment with 300 MPa for 2 min at 25 degrees C inactivated approximately 8 log10 TCID50/ml. A small fraction of the virus population, however, remained resistant to pressure treatments of up to 800 MPa for 10 min. Viruses surviving these extreme pressures showed a cytopathic effect different from that of the untreated viruses. The rotavirus was found to be resistant to PEF treatment at 20 to 29 kV/cm, for which no appreciable reductions in virus titer were observed.

Immunoassay method for quantitative determination of nisin in solution and on polymeric films.

AIMS: To develop a non-competitive direct immunoassay method for quantifying nisin in solution or adsorbed to surfaces. METHODS AND RESULTS: The developed method differs from traditional ELISA in pre-forming a complex of the nisin antibodies and the secondary antibody conjugate before addition to the nisin-coated solid phase. The modifications may help decrease interference from the nisin degradation molecules and reduce non-specific adsorption of secondary antibody conjugate. The new method has a detection limit of 65 ng nisin and correlates well (r=0.982) with the agar diffusion bioassay. CONCLUSIONS: A new sensitivity method was developed to determine the amounts of nisin adsorbed to a polymeric surface. SIGNIFICANCE AND IMPACT OF THE STUDY: The new technique can provide a reproducible and accurate method to quantitate nisin molecules in solutions and those bound on polymeric surfaces, and it is free of the limitations of the traditional agar diffusion bioassay.

Prevalence of antibodies against measles virus in Tripoli, The Socialist People's Libyan Arab Jamahiriya.

A compulsory immunization policy against measles was introduced in the Socialist People's Libyan Arab Jamahiriya in 1972. Data are presented to show that a decreased incidence of measles followed this programme. Nevertheless, measles epidemics still occur and the serological status of the population has, therefore, been examined. In the area of Tripoli, measles haemagglutination-inhibiting (HI) antibodies were found at a titre of greater than or equal to 1:10 in 97% of the adult population, and in 78%, 100% and 97.1% of schoolchildren of primary, preparatory and secondary schools respectively. The relatively high HI titres observed, particularly in adults, imply that antigenic restimulation of antibody against measles occurs and thus that coverage by immunization remains inadequate. Increased efforts to improve immunization coverage at an early age are recommended.

Analysis of neutralizing antibody responses against poliovirus types 1, 2 and 3 in the Tripoli area of the Socialist People's Libyan Arab Jamahiriya.

Analysis of the records available show that the introduction in Libya of a compulsory immunization programme against poliomyelitis was followed by a substantial decrease in the incidence of paralytic poliomyelitis. Nevertheless, the annual incidence is still higher than in many western industrialized countries. We have conducted a survey of neutralizing poliovirus antibodies in human sera. In the group aged 19 years and upwards, i.e., those born before compulsory immunization, 65% had detectable neutralizing antibodies against the 3 viruses, and on average 73% were positive for 2 of the 3 virus serotypes and 85% for only one. The overall proportions in schoolchildren 6-18 years old were lower than in adults. In adults and schoolchildren from 6-18 years old, the highest proportion of positives was against type 2 poliovirus. For infants up to 5 years old the figures overall were higher but the type 2 serotype did not predominate. Surprisingly, the anticipated increase in proportions of positive antisera in 7 year olds, following a booster immunization at the time of school entry, was not apparent, implying inadequate coverage. The results appear to show that stricter measures to control the rate of coverage of immunization are required to reduce the relatively high incidence of paralytic poliomyelitis in Libya.

Serological survey for toxoplasmosis in Tripoli, S.P.L.A.J. Libya.

Toxoplasma antibodies were found at a titre of 1:16 or above in 51.6% of 2000 adult males, in 43.4% of 300 adult females, and in 43.7% of 1980 schoolchildren (7-18 years of age) from the area of Tripoli (Libya). However, 69.4% of a group of 1921 female patients with a history of abortion and clinically suspected of being infected with T. gondii had Toxoplasma antibodies, and 18.6% of them exhibited serological evidence of recent infection (4-fold or greater increase in antibody titre over 2-3 weeks).