[Pseudomonas aeruginosa isolated in immunocompromised patients: antimicrobial resistance, serotyping, and molecular typing].

OBJECTIVE

Our study dealt with antibiotic resistance and serotypes of Pseudomonas aeruginosa strains isolated from immunocompromised patients in the National Bone Marrow Transplant Center of Tunis as well as molecular typing of ceftazidime resistant strains (CAZ-R).

DESIGN

We studied a total of 87 non-replicate P. aeruginosa isolates from 36 patients (84 strains) or the hospital environment (3 strains).

RESULTS

Rates of antimicrobial resistance were 36% for ceftazidime, 16% for imipenem, 38% for amikacin, and 57% for ciprofloxacin. The 31 CAZ-R strains were associated with O:11 serotype in 84% of the cases. Genetically characterization of CAZ-R strains by Pulsed Field Gel Electrophoresis (PFGE) after digestion of genomic DNA with SpeI revealed 2 genotypic groups. The first was composed of strains isolated from one outpatient between November 1998 and April 1999. Resistance phenotypes of these strains varied after use of antimicrobial drugs. The second was predominant (18/31 CAZ-R strains) in both hematology and graft units and persisted from June 1998 to June 2000 among 5/8 patients. These strains had O:11 serotype in 78% of the cases. The strains of this group were not isolated on patient admission and were isolated from 2 washbasins in the graft unit in May 1999.

CONCLUSION

These results suggest the spread of multidrug-resistant O:11 P. aeruginosa clone from a tap water among hospitalized patients in our center, emphasizing the need of standard control of washbasins to eradicate this reservoir.