The serotypes of 88 nonreplicate nosocomial Pseudomonas aeruginosa
isolates from 11 Greek hospitals were studied in relation to their
antibiotic susceptibilities. Rates of resistance to beta-lactams,
aminoglycosides, and quinolones ranged from 31 to 65%, except for those
to ceftazidime (15%) and imipenem (21%). Four serotypes were dominant:
O:12 (25% of isolates), O:1 (17%), O:11 (16%), and O:6 (10%),
Multidrug resistance rates in the major serogroups O:12 (91%) and O:11
(79%) were higher than those in serogroups O:1 (40%) and O:6 (43%).
Further typing with respect to pulsed-field gel electrophoresis patterns
following XbaI digestion of genomic DNA discriminated the isolates into
74 types, Pulsed-field gel electrophoresis revealed that the ubiquitous
O:12 group was genetically homogeneous, since 95% of strains belonged
to two clusters of genotypic similarity, while the O:11 strains, present
in 8 of the 11 hospitals, were distributed among five such clusters.
Therefore, apart from the already reported O:12 multidrug-resistant
European clone, an O:11 population, characterized by a serotype known to
be dominant in the environment and the hospital in several parts of the
world, but previously not associated,vith multidrug resistance to
antibiotics, has progressed to a multidrug-resistant state
