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Survival of Pseudomonas aeruginosa in modified Romanowsky staining solutions
Richard Duffield1, Hui-San Wong1, Darren J Trott1
1School of Animal and Veterinary Sciences, University of Adelaide, Roseworthy Campus, Roseworthy, SA, 5371, Australia.
Background:
Anecdotal reports suggest that rapid staining solutions can become contaminated with micro-organisms, especially Pseudomonas aeruginosa.
Hypothesis/Objectives:
To determine whether inoculation of rapid Romanowsky-type stains with P. aeruginosa results in viable bacterial contamination, which could lead to cross-contamination of slides during cytological staining.
Methods:
Pseudomonas aeruginosa was inoculated into clean and organically contaminated staining solutions (fixative, eosin and methylene blue) and positive (broth) and negative (bleach) control solutions. Subsequent viability and survival were detected by measuring colony-forming units per millilitre at various time points up to 2 weeks. Each sample was stained and microscopically examined to determine whether bacteria were visible.
Results:
No bacteria could be cultured at any time point from the bleach or fixative solution. In clean eosin and methylene blue staining solutions, viable bacteria were recovered for up to 1 h, but by 24 h all bacteria were dead. In staining solutions contaminated with hair and dead skin cells, bacteria survived in methylene blue for up to 1 h, and viable bacteria persisted in the eosin stain for 2 weeks. In solutions containing viable organisms, the bacteria could be observed by microscopic examination; no bacteria were visible when the solutions contained no viable organisms.
Conclusions And Clinical Importance:
Pseudomonas aeruginosa can survive in commonly used staining solutions for variable periods of time, but is unable to proliferate. Although theoretically this might complicate cytological interpretation and subsequent diagnosis, the likelihood of this in clinical practice appears remote when the correct staining technique is used.
Insights
Pseudomonas aeruginosa can survive in some rapid staining solutions but cannot proliferate. Bacterial contamination of cytological slides is unlikely with proper staining techniques.
Area of Science:
- Microbiology
- Cytology
- Laboratory Science
Background:
- Anecdotal evidence suggests rapid staining solutions may harbor microorganisms.
- Pseudomonas aeruginosa is a common contaminant of laboratory reagents.
Purpose of the Study:
- To investigate the viability of Pseudomonas aeruginosa in rapid Romanowsky-type stains.
- To assess the risk of cross-contamination in cytological staining.
Main Methods:
- Inoculation of staining solutions (fixative, eosin, methylene blue) with P. aeruginosa.
- Monitoring bacterial viability using colony-forming units over 2 weeks.
- Microscopic examination of stained slides.
Main Results:
- No bacterial growth in fixative or bleach controls.
- P. aeruginosa survived up to 1 hour in clean eosin and methylene blue.
- In contaminated solutions, bacteria persisted for 2 weeks in eosin and 1 hour in methylene blue.
- Viable bacteria were microscopically visible.
Conclusions:
- Pseudomonas aeruginosa can survive but not proliferate in common staining solutions.
- The risk of clinically significant contamination is low with correct staining techniques.
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