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Outbreak caused by tobramycin-resistant Pseudomonas aeruginosa in a bone marrow transplantation unit
O Lyytikäinen1, V Golovanova, E Kolho
1Department of Infectious Disease Epidemiology, National Public Health Institute, Helsinki, Finland.
Abstract:
Between May and August 1995, 5 patients in a bone marrow transplantation (BMT) ward developed bacteremia caused by Pseudomonas aeruginosa resistant to tobramycin (TRPA). Previously, isolates of TRPA had been limited to patients who were treated in 1 intensive care unit (ICU) of this tertiary care teaching hospital in Helsinki, Finland. To study whether the outbreak was caused by a single or multiple strains of P. aeruginosa, 102 isolates of TRPA from clinical samples obtained from different hospital units and 22 isolates obtained from the hospital environment were characterized by pulsed-field gel electrophoresis. All isolates from hematological patients produced 1 unique fragment pattern, which was also isolated from 3 ICU patients before the BMT ward outbreak began as well as from 5 shower heads in the BMT ward. The outbreak in the BMT ward was successfully controlled by eradicating the probable environmental source--contaminated hand showers--but the endemic infections continued in the ICU.
Insights
A Pseudomonas aeruginosa outbreak in a bone marrow transplant ward was traced to contaminated shower heads. Eradicating the source controlled the outbreak, but infections persisted in the intensive care unit.
Area of Science:
- Infectious Diseases
- Microbiology
- Hospital Epidemiology
Background:
- Tobramycin-resistant Pseudomonas aeruginosa (TRPA) infections previously occurred in an intensive care unit (ICU).
- An outbreak of TRPA bacteremia occurred in a bone marrow transplantation (BMT) ward between May and August 1995.
Purpose of the Study:
- To investigate the source and strain relatedness of TRPA isolates during the BMT ward outbreak.
- To determine if the outbreak was caused by a single or multiple strains of P. aeruginosa.
Main Methods:
- Pulsed-field gel electrophoresis (PFGE) was used to characterize 102 clinical TRPA isolates and 22 environmental isolates.
- Isolates were obtained from clinical samples across different hospital units and from the hospital environment, including shower heads.
Main Results:
- A unique P. aeruginosa fragment pattern was identified in all hematological patients during the BMT ward outbreak.
- This unique strain was also found in 3 ICU patients prior to the BMT outbreak and in 5 BMT ward shower heads.
- Control measures targeting the contaminated showers successfully halted the BMT ward outbreak.
Conclusions:
- Contaminated hospital showers served as the probable environmental source of the TRPA outbreak in the BMT ward.
- While the BMT outbreak was controlled, endemic TRPA infections continued in the ICU, suggesting a broader or persistent issue.