Question

Crystal hasn't been feeling well for the past day. She has frequent urges to urinate and when she does she feels pain urinating and only urinates a few drops. She visits her family physician and the physician asks her to go to the lab and have a urine culture done.

Crystal does this immediately.
The lab gets her sample and does a urine culture and antibiotic sensitivity test on the bacterium that is found in her urine in significant numbers.
The results from the lab are as follows:
Growth of >100,000/ml E. coli per ml urine.
Sensitivity testing by Kirby Bauer test:
Ampicillin R
Nitrofurantoin I
Tetracycline I
Trimethoprim-sulfa S
Why does the report call the findings a significant number? What does this have to do with the management of this infection?
A.Only cultures showing >100,000/ml of E.coli will be treated
B.Only cultures showing < 100,000/ml of E. coli will be treated
C.Only cultures showing growth of several bacteria in large numbers will be treated
D.Only cultures with >100,000/ml of S. saphrophyticus will be treated

Answer 1

Option A is correct as only urine cultures showing >100,000/ml of E. coli indicate a significant infection and will be treated accordingly. This threshold helps differentiate true infection from contamination, and antibiotic sensitivity informs effective treatment.

Step-by-step explanation:

When a urine culture shows a growth of >100,000/ml of E. coli, it indicates a significant number, which suggests an active urinary tract infection (UTI). This threshold is used to differentiate between contamination and true infection; lower counts might represent contamination. Therefore, option A is correct: Only cultures showing >100,000/ml of E.coli will be treated. This is critical for the management of the infection because it ensures that antibiotics are prescribed when there is a high likelihood of an actual infection rather than treating non-significant bacterial presence that may not cause symptoms. The antibiotic sensitivity results inform the clinician which medications are likely to be effective in treating the infection. In Crystal's case, Trimethoprim-sulfa being sensitive (S) suggests it would be an effective treatment for her UTI.