"persistent stain" is a correct and usable phrase in written English.
It can be used when describing something that is difficult to remove or get rid of, either physically or metaphorically. Example: Despite my best efforts, the wine spill left a persistent stain on my white shirt.
Suspicious glances were shot in Hermitage's direction, threatening to leave a persistent stain on her reputation.
He called the problem "a persistent stain on the Fire Department's record".
In his decision, the judge highlighted how "black and other minority firefighters have been severely underrepresented," characterizing that as a "persistent stain on the Fire Department's record".
Calling the practice a "persistent stain on the Fire Department's record," Judge Garaufis ordered the city to give 300 minority applicants priority hiring status and retroactive seniority and to financial compensate 7,400 more who had taken the test, payments that the Justice Department estimates will total $63.5 million.
Affirmative action is a necessary and still insufficient remedy for the persistent stain of American racism.
Mayor Bloomberg seems to be falling in with a long line of elected and appointed officials who have failed to correct what Judge Garaufis described as "a persistent stain on the Fire Department's record".
Repeat steps for a persistent grease stain.
There was high background staining of the adipocytes in these paraffin-embedded samples, demonstrated by a persistent staining pattern in these cells in Lrp5−/− glands, where the specific basal cell-associated stain is absent.
Of the remaining tumours, we performed mutational analysis on 330 tumours, and assessed persistent staining and staining intensity in 356 tumours.
Both the early-stage tumours lacking persistent staining and those cancers with p53 staining may later undergo p53 mutation and become aggressive and invasive.
Persistent staining alone was far more prevalent than intense staining, although there was a significant correlation between the two measures (Table 2 (b)).
