Is a urinary tract infection with two plus white blood cells serious? The severity of urinary tract infection is determined by the number of white blood cells in the urine routine. Leukocytes equal to two plus sign proves that it is a moderate urinary tract infection, you can use the second generation of cephalosporins, quinolones antibiotics for anti-infective treatment, usually use cefuroxime or colestipol. Urine white blood cells less than a plus sign proved to be a mild urinary tract infection, greater than or equal to three plus sign is a severe urinary tract infection, so urine white blood cells two plus sign belongs to a moderate urinary tract infection, not too serious.