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Epidemiology of Pseudomonas aeruginosa infections: determination by pyocin typing
Abstract:
The epidemiology of hospital infections due to Pseudomonas aeruginosa was investigated by pyocin typing. The typing method, which determined the pyocin activity of clinical isolates of P. aeruginosa on 27 indicator strains, was 43.7% reproducible, but elimination of 9 indicator strains doubled the reproducibility and yielded more readable pyocin inhibition zones. Seventy-eight of 1,084 isolates (7.2%) were untypable. In the second part of the study, P. aeruginosa was isolated from 110 patients (5.4% of all admissions) in a 3-month period and typed with the revised method. Twenty pyocin types were identified, 10 of which were obtained from five or more patients. P. aeruginosa was isolated from 45 of 353 environmental samples, including water fountains, ice machines, bar soaps, and germicide solutions for toilet brushes. Twenty percent of the environmental samples were untypable but, among typable strains, the five most common environmental strains were the same as the strains most frequently isolated from patients. The organism was frequently isolated from noses (39%), throats (39%), and stools (29%) of patients with P. aeruginosa infections or colonizations in urine, sputum, surgical wounds, or skin lesions. Six of eight patients had P. aeruginosa in their tracheostomy wounds. Autoinfections by strains already acquired on carrier sites may be significant.
Insights
Hospital infections caused by Pseudomonas aeruginosa were studied using pyocin typing. A revised method improved reproducibility, revealing common environmental strains matching patient isolates, suggesting autoinfection is a significant factor.
Area of Science:
- Medical Microbiology
- Infectious Diseases Epidemiology
Background:
- Pseudomonas aeruginosa is a significant cause of hospital-acquired infections.
- Effective epidemiological surveillance requires reliable methods for strain differentiation.
Purpose of the Study:
- To investigate the epidemiology of Pseudomonas aeruginosa hospital infections using pyocin typing.
- To refine the pyocin typing method for improved reproducibility and clarity.
Main Methods:
- Pyocin typing of clinical and environmental Pseudomonas aeruginosa isolates using 27 indicator strains.
- Revision of the typing method by reducing indicator strains to enhance reproducibility.
- Isolation and typing of P. aeruginosa from patients and environmental sources over a 3-month period.
Main Results:
- The initial pyocin typing method had 43.7% reproducibility; revision doubled this and improved zone readability.
- Twenty distinct pyocin types of P. aeruginosa were identified from 110 patient isolates.
- Common environmental P. aeruginosa strains, isolated from water, ice, and soaps, matched frequently isolated patient strains.
Conclusions:
- A revised pyocin typing method enhances the epidemiological investigation of Pseudomonas aeruginosa.
- Environmental contamination likely contributes to patient P. aeruginosa infections.
- Autoinfection from patient carrier sites (nose, throat, stool) is a significant factor in P. aeruginosa infections.