Investigation of microbial contamination of commercial Romanowsky stain variant solutions used in veterinary clinics

Diff-Quik (DQ) staining is widely used in clinical practice for its ease of use and rapid results. However, its potential contamination remains a concern.

This study aimed to investigate DQ solution contamination in veterinary hospitals and identify factors affecting it through a questionnaire on stain usage practices.

A survey was conducted to assess the use of DQ staining in local animal clinics. Samples of DQ solution II collected from each hospital participating in the survey were cultured and analysed microscopically for contamination.

A total of 67 DQ stain samples were collected from veterinary hospitals, of which 10 (14.92%) were found to be contaminated with pathogens. Bacterial cultures were positive in six of the samples (8.95%); four were contaminated with Staphylococcus pseudintermedius, one with Stenotrophomonas maltophilia and one with Bacillus haynesii. Malassezia pachydermatis was found in the remaining contaminated samples (n = 4, 5.97%). Statistical analysis revealed that the significant factors associated with DQ stain contamination were the use of a dropper, direct immersion of slides in the dye, average weekly usage and periodic replacement of the solution (p < 0.05).

This study confirms DQ solution contamination in general veterinary practice. To minimise contamination risk, using a dropper for stain application instead of direct specimen immersion in the stain is recommended. Furthermore, in hospitals where DQ solutions are frequently employed, the stain should be periodically replaced or examined under a microscope.