Midstream voided urine collection from an apparently healthy

As part of a routine physical examination, a urinalysis is performed on a midstream voided urine collection from an apparently healthy (asymptomatic) 8-year-old girl. The following results are obtained on a fresh specimen:

 

Physical Appearance
Color Yellow
Transparency Hazy
Chemical Screening
pH 6.0
Specific Gravity 1.010
Protein (strip) 30mg/dL (1+) (SSA) 1+
Blood Neg
Nitrate Neg
Leukocyte esterase Pos
Glucose Neg
Ketones Neg
Bilirubin Neg
Urobilinogen Norm
Microscopic examination of urinary sediment
RBC’s 0-3/hpf
WBC’s 10-25/hpf
epithelial cells few (squamous)
bacteria moderate (2+)

After reviewing the results of the urinalysis the attending physician requests a gram stain and urine culture

Microbiology Results:
Gram Stain Gram-positive cocci
Urine Culture >100,000 CFU/mL of Enterobacter species

1. Of the above results, which urinalysis findings are abnormal?

2. This lab does not perform a microscopic examination on all routine urinalysis tests.  Explain why the microscopic examination of the urine sediment was performed in this case.

3. Can the urine collection already tested be gram stained and cultured? Why?

4. Explain the negative nitrate results and the presence of bacteria in the urine sediment.

5. Would these results be more likely to represent an upper or lower urinary tract infection? Why?