Atypical rotavirus identified from young children with diarrhoea in South Africa.

The study was undertaken for antigenic characterization of rotavirus strains isolated from South African children. During July 1996-July 1997, an epidemiological surveillance of rotavirus-associated gastroenteritis was carried out in Pretoria and Gauteng provinces. In total, 1,229 diarrhoeal faecal samples were collected from a pathology laboratory. Of 389 (32%) rotavirus strains detected, most (97%) were group A rotaviruses by serological assay. However, 12 rotavirus strains identified did not apparently carry the common group A-specific antigen as determined by both commercial and monoclonal antibody-based ELISAs. Electrophoretic analysis of the viral RNA genome revealed that these strains shared a common electropherotype and that this resembled the group A rotavirus constellation of RNA segments. Furthermore, the conserved terminal sequences of the group A VP6 and VP7 genes could not be targeted by standard reverse transcriptase-polymerase chain reaction with a routine set of primers to the VP6 or VP7 genes. These strains present an interesting phenotypic variation of the recognized rotaviruses and warrant further characterization.

Thermo-labile stability of sigmaH (Spo0H) in temperature-sensitive spo0H mutants of Bacillus subtilis can be suppressed by mutations in RNA polymerase beta subunit.

We isolated novel temperature-sensitive mutants of spo0H, spo0H1 and spo0H5, having E61K and G30E amino-acid substitutions within the sigmaH protein, respectively, and located in the highly conserved region, "2", among prokaryotic sigma factors that participates in binding to core enzyme of RNA polymerase. These mutants showed a sporulation-deficient phenotype at 43 degrees C. Moreover, we successfully isolated suppressor mutants that were spontaneously generated from the spo0H mutants. Our genetic analysis of these suppressor mutations revealed that the suppressor mutations are within the rpoB gene coding for the beta subunit of RNA polymerase. The mutations caused single amino-acid substitutions, E857A and P1055S, in rpoB18 and rpoB532 mutants that were generated from spo0H1 and spo0H5, respectively. Whereas the sigmaH-dependent expression of a spo0A-bgaB fusion was greatly reduced in both spo0H mutants, their expression was partially restored in the suppressor mutants at 43 degrees C. Western blot analysis showed that the level of sigmaH protein in the wild type increased between T0 and T2 and decreased after T3, while the level of sigmaH protein in spo0H mutants was greatly reduced throughout growth, indicating that the mutant sigmaH proteins were rapidly degraded by some unknown proteolytic enzyme(s). The analysis of the half-life of sigmaH protein showed that the short life of sigmaH in spo0H mutants is prolonged in the suppressor mutants. These findings suggest that, at least to some extent, the process of E-sigmaH formation may be involved in stabilization of sigmaH at the onset of sporulation.

Group B and C porcine rotaviruses identified for the first time in South Africa.

The incidence of rotavirus at a pig farm in Gauteng was determined by polyacrylamide gel electrophoresis (PAGE). Faecal specimens were collected from 172 litters over a 6-month period. Rotavirus was detected in 37.8% of piglets exhibiting signs of scouring. When these PAGE patterns were examined, 84.6% group A, 4.6% group B and 10.8% group C rotaviruses were observed. A few specimens subsequently collected from other farms in the Gauteng. North-West and Northern Provinces also contained group B and C electropherotypes. This is the first report of group B and group C rotaviruses in the South African pig population.

A molecular epidemiological study of porcine rotaviruses.

Diarrhoea in the piglet can lead to stunted growth and neonatal death, with important implications for the pig farmer. During 1993, a pilot study was initiated to monitor the epidemiology of rotavirus infection in piglets with diarrhoea. Bimonthly diarrhoeal faecal specimens were collected from scouring piglets less than 6 weeks of age on a pig farm in the Northern Transvaal. The stool specimens were examined by a commercial enzyme-linked immunosorbent assay (Rotavirus EIA, IDL, Jerusalem). In total, rotavirus antigen was detected in 24% of the litters by the ELISA, which is directed at the group A rotavirus antigen. Rotavirus was found to occur throughout the year and predominantly in piglets 4 weeks old. Polyacrylamide electrophoretic analysis of the viral RNA genomes showed the presence of four distinct strains of Group A rotaviruses circulating on this farm. This study highlights the natural diversity of rotavirus strains circulating on a single farm and may indicate the importance of rotavirus infection in piglets with diarrhoea in South Africa.