I usually have a glass of wine every night and have to have a drug and alcohol screening for a new job. will this affect the results of the screening?

Probably not: But this depends on when you had the glass of wine relative to when the testing was done and whether you indicated to your potential employer that you usually have this in the evening. The probability is that your blood will no longer contain alcohol 8 hours after one glass of wine. You could also forego the wine the night before the test.