The serology of Pseudomonas aeruginosa analysed by means of quantitative immunoelectrophoretic methods. V. Thermostability, resistance to degradation by plasmin activity and storage conditions of a polyvalent P. aeruginosa reference standard-antigen.

The stability of a polyvalent Pseudomonas aeruginosa antigen (St-Ag) was analysed under different experimental conditions by quantitative immunoelectrophoretic methods. St-Ag did not undergo proteolytic degradation by plasmin which is present in the corresponding polyvalent rabbit antiserum (St-Ab) against St-Ag. Storage at -30 degrees C for up to 4 years caused no qualitative changes in St-Ag and, after 1 year, only minor quantitative changes could be revealed. Repeated thawing and freezing caused no changes in St-Ag whereas storage at 4 degrees C, or at room temperature, caused gradual degradation of most of the antigens of St-Ag, beginning after 1 week. Heating up to 40 degrees C for 2 min did not change St-Ag, but heating for longer periods of time or at higher temperatures gradually destroyed most of the antigens of St-Ag. The most thermostable antigen in St-Ag was number 37 which is related to the group specific O antigens.