[Permanence and parellelism of serogroups of Pseudomonas aeruginosa in hospitalized patients (author's transl)].

The determination of O-antigens of 248 serial isolates of Ps. aeruginosa from 50 patients with respiratory, urinary tract or wound infections reveals that over a period of 41 (8-178) days in 12% of cases a change, in 88% no variation of serogroup at the infection site occurs. Simultaneous incidence of different serogroups in the same specimen is not observed. 55 parallel isolates from the various lesions of 26 multiinfected patients have in 46% of cases different serogroups, in 54% the same serogroup. The striking permanence of serogroups at a particular infection site indicates that the O-antigens of Ps. aeruginosa remain constant under natural infection conditions. A change in serogroup suggests--considering the frequent parallelism of different serogroups--reinfection by a new strain.