Serotyping Pseudomonas aeruginosa was effectuated in 833 strains isolated from pacients of various hospital Centers and of normal population. To the determination of the antigenic O groups (Habs classifications), we used a technic of agglutination in slides OMS, putting in contact the alive germen with the 15 serums anti-O (Pasteur Institut, Paris). The most frequent serogroups in decreasing order of importance, spread among the whole population are: 0:11, 0:3, 0:6, 0:1, 0:4, 0:5, 0:7, 0:10, 0:13, 0:2, 0:12, 0:9, 0:8, 0:14, and 0:15. The serogroup 0:11 is clearly dominant among hospital population (31,54 %). In respect to the normal population, the sequence is the following : 0:6, 0:1, 0:3, 0:11, 0:5, 0:2, 0:9, 0:7, 0:13, 0;10, O;4, 0;8, 0;12, 0;14, 0;15, and the serogroups 0:6 and 0:1 are the most frequent (31,05 %). This simple and quick method of determination of the serogroups of Pseudomonas aeruginosa can be very helpful in the epidemiological study on the Pseudomonas pyocyanea. The knowledge of the most common serogroups among portuguese population, wether hospitable or not hospitable, brought an important contribute to our study on: 1 — The ecology of the pyocyanic bacillus in the hospital circle. 2 — lhe mislead of exogenous or endogen infections of Ps. aeruginosa in the Intensive Care Centers, with tracheatomy (Reanimation Center). 3 — The serodiagnostic of the hospital strains made in order to establish the bases of an eventual anti-pyocyanic vaccination of the pacients with a great danger of infection. 4 — The confrontation of the results of the serotyping with the others two epidemiological «markers»: the lysotyping and the pyocynotyping. This work led us to a greater exactness in the epidemiological inquests about Pseudomonas aeruginosa made in Portugal, and allow us to compare our results with other countries’ ones.

Trabalho original publicado no Vol. 25, 1975. O aparecimento de certas gralhas determinou a sua reimpressão