An immunoassay for the rapid and specific detection of three sialidase-producing clostridia causing gas gangrene.

A rapid and methodologically unusual diagnostic test was developed for the specific detection of Clostridium perfringens, C. septicum and C. sordellii, which cause clostridial myonecrosis. Sialidases (EC 3.2.1.18) secreted by these bacterial species were bound to polyclonal antibodies raised against the respective enzyme and immobilized onto microtiter plates. The activity of bound sialidase was determined with the fluorogenic substrate 4-methylumbelliferyl-alpha-D-N-acetylneuraminic acid. The assay permits the detection of a minimum sialidase activity of about 0.1-1 mU/ml of sample solution within 2 h. The sensitivity of the test was reduced by about three-fold for sialidase activities in samples containing 50% serum. Only a few, low cross-reactivities, which never exceeded 10% of the homologous reaction, were observed with 12 sialidases from other bacterial sources. Clinical isolates of the three clostridial species were analysed by this assay and gave positive signals in the homologous test. The assay for the detection of C. perfringens was applied to nine samples from patients suspected to be suffering from clostridial myonecrosis. There was a high correlation between the results of the immunoassay and the bacteriological analysis of infection.

Early Changes in Gene Expression during the Transition from Vegetative to Generative Growth in the Long-Day Plant Sinapis alba.

Changes in gene expression during flower formation were studied in the long-day plant Sinapis alba. The day length dependence was exploited to synchronize flower formation in a large population of mustard plants. After an inductive light treatment, apices were harvested after different lengths of time, and changes in gene expression were analyzed. Two major groups of genes were identified whose expression was affected during flower formation. Transcripts of the first group (group I) were present at low concentration in the apex of noninduced plants. They began to accumulate strongly after the end of the inductive light period. They reached a maximum 2 days to 10 days after flower induction and then declined slowly. Transcripts of the second group of genes (group II) could be detected for the first time 10 days after flower induction. Within a very short time, these transcripts accumulated dramatically and reached a maximum 15 days after flower induction before beginning to decline. They dropped beyond the limit of detection before the flower reached maturity.