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Pseudomonas aeruginosa infection in hospital: a comparison between 'infective' and 'environmental' strains
Abstract:
One hundred and fifty-six infections or episodes of infection associated with Pseudomonas aeruginosa in six hospitals over 14 months were investigated. Pyocine typing and serotyping suggested that 145 distinct episodes had occurred, caused by 78 different strains. During this period 15 distinct strains were isolated from the environment at one of the hospitals; 12 of these were apparently unassociated with infection in the same ward during the period, and 4 were of types not encountered in infective processes at any hospital. There appeared to be a rather higher proportion of unclassifiable pyocine inhibition patterns among the environmental strains; in general these strains also produced smaller amounts of haemolysin. If failure to produce haemolysin in vitro is correlated with lack of virulence in vivo, this may partially explain the sporadic nature of hospital infection with Ps. aeruginosa, despite the prevalence of strains of this species in the environment.
Insights
Pseudomonas aeruginosa strains in hospitals were studied. Environmental strains showed lower virulence, potentially explaining the sporadic nature of hospital infections despite their prevalence.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Environmental Microbiology
Background:
- Pseudomonas aeruginosa is a common cause of hospital-acquired infections.
- Understanding the sources and characteristics of circulating strains is crucial for infection control.
Purpose of the Study:
- To investigate the diversity of Pseudomonas aeruginosa strains causing infections in hospitals.
- To compare clinical isolates with environmental strains to understand transmission dynamics.
Main Methods:
- Pyocine typing and serotyping were used to differentiate bacterial strains.
- Infections and environmental samples were collected over 14 months across six hospitals.
- Haemolysin production and pyocine inhibition patterns were analyzed.
Main Results:
- 156 infection episodes were linked to 78 distinct Pseudomonas aeruginosa strains.
- 15 distinct environmental strains were identified at one hospital.
- Many environmental strains were not associated with infections and showed reduced haemolysin production.
Conclusions:
- Environmental Pseudomonas aeruginosa strains may have lower virulence.
- Reduced haemolysin production in vitro could correlate with decreased in vivo virulence.
- This difference may explain the sporadic nature of hospital infections despite environmental prevalence.