Leukocyte esterase test, Nitrite test

Leukocyte esterase + = presence of neutrophils (Bacterial infection)

Nitrite + = Gram- negative Most enterobacteria (gram-negative enteric rods) are able to form nitrite from nitrate

Easy enough! It gets trick when the patient is Leukocyte esterase positive and Nitrite negative.

So you know it is going to be Gram positive bacteria causing the infection. Most likely would be Staph. saprophyticus (2nd most common cause of UTI in sexually active females). The other possibility which is not as common is Enterococcus faecalis (gram positive, catalase-negative)