When you take a urine sample it is sent for an MC&S (microscopy, culture and sensitivities). So they culture it and the result will be returned to the doctor with antibiotics listed and whether they are sensitive or resistant to them. It takes about 48 hours to get a result but often once the specimen is received the doctor will commence on a broad spectrum antibiotic as a cover until the result is received. They will do this if the infection is producing troublesome symptoms.
I don't know your circumstances GJ but this is a general outline of possible causes and tips to possibly avoid UTI's...
Ural, or something similar, can be very helpful at reducing the pain and burning associated with UTI's
Unfortunately some women are prone to recurrent/chronic UTI's for no obvious reason and they can run in families. It is also unfortunate that the urethra in a woman is only about 4cm long, so very easy for bacteria to travel up to the bladder.
Cranberry capsules are quite effective for many women as a long term way of reducing the amount of UTI's you get.
Also Ural sachets, when you first get that feeling that a UTI is starting, can stop one in it's tracks.
Nylon underpants or pantyhose without a gusset can cause issues for some women, probably more so with thrush but also UTI's. Stick to cotton underwear and gusseted stockings. I know it sounds like an old wives tale but tight clothing can cause UTI's for the same reasons as nylon stockings can...it creates a warm, moist, non breathable environment.
If you wear pads then that also creates a warm moist environment that is ideal for fungal infections.
Perfumed soaps and powders can cause irritation and external infection which track up into the bladder and cause infection.
I know when you have a UTI and are going to the toilet frequently, and it feeling like you are passing razor blades, the temptation is to drink less but the more concentrated your urine becomes the more irritant it is to the bladder.
The contraceptive pill can cause UTI's in some women due to the hormonal changes it causes.
Urinating shortly after sex helps to flush away any bacteria that may have entered the urethra during sex.
Dusty.