Nosocomial outbreaks caused by multidrug-resistant (MDR) Pseudomonas aeruginosa have been associated to fibrocystic patients and isolates harboring metallo-beta-lactamase (MBL) genes. Genotyping is an important tool for interpreting bacterial nosocomial outbreaks and implementing adequate control strategies. The aim of this study was to evaluate whether an outbreak of MDR P. aeruginosa occurring in different hospitals was due to a unique clone or independent isolates. From 2000 to 2003, 108 P. aeruginosa were recovered from colonized/infected inpatients in hospitals of São Luís, Maranhão, Brazil. The susceptibility test was performed with antipseudomonal drugs, and the presence of MBL genes were verified by PCR. Isolates were genotyped by pulsed-field gel electrophoresis (PFGE). The majority of strains was multiresistant including a great number presenting the colistin-only-sensitive (COS) profile. PFGE analysis revealed 54 genotypes, with predominance of three major COS clones (A, C, and E) coexisting at different moments and hospitals. Clone A harbored the bla(SPM) gene. Eight unique genotypes also had the COS profile. Other eight MDR genotypes presented isolates with differences in resistance profiles. Here we detected, for the first time, the coexistence of COS P.aeruginosa genotypes disseminated in several hospitals during long periods, attacking patients under various clinical conditions.