E. Coli

[oneillg]

My dog has just been diagnosed with a high load of E. Coli present in a bladder culture that was done last week. (She has no symptoms of any infection, but a serial urinalysis showed that the specific gravity of her urine was out of the normal range for all but 1 out of the 6 samples), so the DVM performed the bladder culture, fearing the start of kidney malfunction. (My dog is a 7 year old Chocolate Lab mix.)

My questions are:

1. How could she have contracted this infection?
2. Is it normal for her to not present any symptoms at all (my reading on this suggests that diarrhea would be common)?
3. Are my other dog, myself, and my family at risk of infection?
4. The doctor is recommending a long-term course of antibiotics - is this the best treatment?

Any information you could provide on the subject would be greatly appreciated!

Regards,
Gigi Kolt