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Cross-colonisation with Pseudomonas aeruginosa of patients in an intensive care unit
D C Bergmans1, M J Bonten, F H van Tiel
1Department of Internal Medicine, University Hospital Maastricht, The Netherlands.
Background:
Ventilator-associated pneumonia (VAP) caused by Pseudomonas aeruginosa is usually preceded by colonisation of the respiratory tract. During outbreaks, colonisation with P aeruginosa is mainly derived from exogenous sources. The relative importance of different pathways of colonisation of P aeruginosa has rarely been determined in non-epidemic settings.
Methods:
In order to determine the importance of exogenous colonisation, all isolates of P aeruginosa obtained by surveillance and clinical cultures from two identical intensive care units (ICUs) were genotyped with pulsed field gel electrophoresis.
Results:
A total of 100 patients were studied, 44 in ICU 1 and 56 in ICU 2. Twenty three patients were colonised with P aeruginosa, seven at the start of the study or on admission and 16 of the remaining 93 patients became colonised during the study. Eight patients developed VAP due to P aeruginosa. The incidence of respiratory tract colonisation and VAP with P aeruginosa in our ICU was similar to that before and after the study period, and therefore represents an endemic situation. Genotyping of 118 isolates yielded 11 strain types: eight in one patient each, two in three patients each, and one type in eight patients. Based on chronological evaluation and genotypical identity of isolates, eight cases of cross-colonisation were identified. Eight (50%) of 16 episodes of acquired colonisation and two (25%) of eight cases of VAP due to P aeruginosa seemed to be the result of cross-colonisation.
Conclusions:
Even in non-epidemic settings cross-colonisation seems to play an important part in the epidemiology of colonisation and infection with P aeruginosa.
Insights
Cross-colonisation by Pseudomonas aeruginosa is a significant factor in respiratory tract colonisation and ventilator-associated pneumonia (VAP) even in non-outbreak settings. This highlights the importance of infection control measures to prevent patient-to-patient transmission in intensive care units (ICUs).
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Critical Care Medicine
Background:
- Ventilator-associated pneumonia (VAP) caused by Pseudomonas aeruginosa often follows respiratory tract colonization.
- In outbreaks, P. aeruginosa colonization is typically exogenous, but its role in endemic settings is less understood.
Purpose of the Study:
- To determine the significance of exogenous sources in P. aeruginosa colonization and VAP in non-epidemic intensive care unit (ICU) settings.
- To evaluate the contribution of cross-colonization to the epidemiology of P. aeruginosa.
Main Methods:
- Genotyping of P. aeruginosa isolates from surveillance and clinical cultures in two ICUs using pulsed field gel electrophoresis.
- Chronological evaluation of genotypically identical isolates to identify cross-colonization events.
Main Results:
- 100 patients were studied; 23 became colonized with P. aeruginosa, and 8 developed VAP.
- Genotyping identified 11 P. aeruginosa strain types, with one type found in 8 patients.
- Eight cases of cross-colonization were identified, contributing to 50% of acquired colonizations and 25% of VAP cases.
Conclusions:
- Cross-colonization plays a substantial role in the epidemiology of P. aeruginosa colonization and VAP, even in endemic ICU settings.
- Findings underscore the need for vigilance and infection control strategies to mitigate transmission.