Characterization of Pseudomonas aeruginosa isolated from drinking water by serogrouping, phage sensitivity and pyocin pattern.

Pseudomonas aeruginosa strains isolated in the years 1977-1981 from drinking water samples fell into a large number of epidemiological units determined on the basis of serogroups, phage sensitivity and pyocin pattern. Strains isolated from water were, as a rule, sensitive to more phages than strains cultured from clinical material. The 427 water isolates fell into 8 serogroups and 31 pyocin patterns; 25.1% were untypable by the pyocin method. The frequency of isolation of different phage patterns varied annually. The most frequent epidemiological unit, comprising 9.1% of the isolates, was (serogroup: phage pattern: pyocin pattern) O1: 2/7/16/21/44/68/73/F7/F8/109/119x/352/1214/M4/C11/C18/C21:12 3567; 73.8% of the strains belonged to epidemiological units each represented by less than 4 strains. The large number of epidemiological units indicated that the distribution system had frequently been polluted with P. aeruginosa at different sites, but the organism was unable to invade the whole water supply system.