Phases of the serological response in Pseudomonas aeruginosa infections

Sixty-four infections due to Pseudomonas aeruginosa in patients of a respiratory intensive care unit were studied. The length of serologically latent period following the appearance of P. aeruginosa decreased with the growing severity of the infection, however, the longest latent period occurred in lethal cases. As the phase of development of peak anti-LPS antibody titres was constant in each group, in fatal infections the serological response developed too late when sepsis had already started. The duration of the persistence of peak titres was also stable. In consequence of a close negative correlation between these two latter parameters, the period from the onset of antibody increase till the beginning of decrease was especially constant, independent of the severity of infection, the duration of the antigenic stimulus and the intensity of the serological response. The rate of decrease was an another stable value. All these refer to an endogenous, time-dependent regulation which, despite existing clinical symptoms and the presence of P. aeruginosa, starts anti-LPS antibody level to decline. Pseudomonas carrier state in convalescence was observed in cases with prolonged persistence of peak titre and with a lower rate of titre decrease.