[Risk of contamination of trypan blue dye after first use].

Purpose: To determine the potential risk of contamination of a trypan blue bottle (TB) after first use and after being stored under different temperature and humidity conditions, as well as to identify possible contamination factors, most frequently involved microorganisms and simultaneously evaluate bacteriostatic and bactericide properties of the dye.

Methods: An experimental and prospective study was carried out, in which 30 TB bottles were divided into 3 groups (A: control, B: refrigerator storage and C: cabinet storage). The dye was suctioned and cultivated in agar blood plates and Sabouraud agar tube. In group A, TB was cultivated immediately after the opening of the bottles (temperature zero - T0), in groups B and C cultivation occurred in T0, T1 (1 day), T2 (2 days), T7 (7 days) and T10 (10 days) after the opening of the bottles. On the 10th day, groups B and C bottles were also submitted to scraping of their inner walls after opening. Concurrently, the inhibitory action measurement test was conducted on the TB dye for the study of bacteriostatic and bactericidal activity.

Results: Cultivation procedures conducted in T0 presented no contamination. Among T1 and T10, added to the scraping there was only one contaminated bottle stored in the refrigerator. The encountered microorganism was Aspergillus niger. It has been proven that the dye does not show bactericide and bacteriostatic properties against the bacteria which were tested.

Conclusions: Under this study's conditions there was no contamination of the bottles stored in cabinets and 1 bottle (10%) stored in the refrigerator showed contamination after opening and initial use. The source of contamination may possibly be the outer part of the product. TB does not show bactericidal and bacteriostatic properties against the tested bacteria and in the applied concentration.