Any chance she's getting any milk in her diet? Some cats react this way when they get any dairy products.

Or it could be food, most pet food is garbage... and its basically anything the food industry deems for us as unfit for our food-treated with toxions to prevent it from ever going into human feed lines, livestock probably eat better then most pets do- because there going to be fed to people..

Innova EVO, Instincts, Ziwi peak, Orijen, are better then most of what is out there.

First, whatever the reason, you must get the diarrhea under control. Cats get dehydrated with diarrhea. Make sure you add plenty of water to her wet food.

Did a culture show her first positive and then negative of campylobacter?

How did the vet propose to treat the diarrhea?

Was she ever wormed? Sometimes eggs do not show up in fecals, so kittens should be wormed as a matter of course.

I had a similar problem with a babykitten I was fostering last summer. My friend, a vet, wrote this when I asked for help:

I presume a fecal was done and no protozoans (Giardia, coccidia, Trictrichomonas) were seen.
An enterovirus is a good possibility (rotavirus, coronavirus, etc.) which would be eliminated by the immune defenses with time.
Bacterial infection (Campylobacter, etc.) is possible also.
We can't rule out food intolerance.

I would give a probiotic (e.g., FortiFlora) + small amounts (half tsp.at the time) of kaopectate (adsorbs toxins) and GRADUALLY switch to another diet that may be better tolerated. Canned food is O.K.
(i think cats do better on canned food; less problems with obesity, diabetes, etc.).
I agree that it's probably not due to the canned food --but I have seen kittens over the years where we had to try several brands before we found one that was well tolerated.

The kaopectate worked; pumpkin, and added cooked white rice to the food did not!

Please pursue the cause if you can't get this under control. Diarrhea can be fatal.

Just as with people, antibiotics can kill off the good bacteria in a cat's digestive tract and cause diarrhea. Did your vet suggest anything to treat it? People often supplement with probiotics when they have to administer antibiotics to their pets. I'd check with the vet (standard disclaimer), but it might be worthwhile to give the kitty some probiotics.

Good idea

Acute Diarrhea- large and small bowel
Primary GI
Overeating
Diet change
Toxins/food poisoning
Food sensitivity
Hemorrhagic enteritis
Parvo (dogs)
Rounds, hooks, whips
Bacteria- Camplyobacter, Salmonella, Clostridia
Sharp/traumatic FB
Intussusception

Extra GI
Acute severe pancreatitis
Addisons
Sepsis/toxemias
Drugs- antibiotics especially

Chronic Small Bowel diarrhea
Primary GI
Food insensitivity
IBD
Food responsive diarrhea
Antibiotic responsive diarrhea
Lymphangectasia
Neoplasia- LSA, adenocarcinoma, mastocytosis, leiomyoma, myosarcoma
Rounds, hooks, giardia, coccidia
Chronic intussusception

Extra GI
Exocine pancreatic insufficiency
Liver failure
Renal failure
Addisons
Hyperthyroidism

Chronic Large Bowel Diarrhea
Primary GI
Fiber responsive colitis
Food sensitivity
Irritable bowel syndrome
Fiber responsive diarrhea
Antibiotic responsive diarrhea
Neoplasia- adenocarcinoma, lymphosarcoma (common in FeLV+ cats at young age)
Whips
Chronic intussusception
IBS
Secondary to chronic small bowel diarrhea
Renal failure

This is from my class notes. The easiest way to approach diarrhea is to first classify it as acute vs chronic (your cat has chronic diarrhea), and then to classify it large bowel or small bowel diarrhea, or both. Here's how to tell the difference between large and small bowel diarrhea:

Small bowel diarrhea: Weight loss, polyphagia, vomiting, abdominal distension, halitosis common; normal to increased frequency of defecation; increased volume, no mucus or hematochezia (bright red blood)

Large bowel diarrhea Weight loss, polyphagia, vomiting, abdominal distension, halitosis uncommon; increased frequency of defecation, normal-decreased volume, mucus present, hematochezia present

Then you work through the list of differentials and test for or eliminate each one as a cause for your cat's diarrhea. Some things are easier to diagnose than others- parasites are easy when present, food allergy or irritable bowel syndrome usually requires intestinal biopsy for example.

First thing I'd do is make sure you know your cat is FeLV and FIV negative; those are fatal diseases and may affect your decision to pursue further diagnostics. FeLV can cause GI lymphoma in very young cats, so I would be especially sure you weren't dealing with an FeLV positive cat who frankly has no hope for recovery before allowing the cat to suffer further and for you to waste money on more diagnostics and treatment. Your vet can test for FeLV and FIV with a few drops of blood and a 10 minute SNAP test while you wait.

In any dog or cat with diarrhea, I deworm with 3-5 days of fenbendazole regardless of stool tests. Parasites don't always shed eggs into the sample you get. Sometimes I also treat for coccidia with ponazuril if I have strong suspicions even if I can't get a sample or don't see any in the sample. It doesn't hurt to deworm and may solve the problem.

You can't test for giardia, coccidia, and bacteria by a sample from home. It must be FRESH and examined immediately, because once those bugs stop moving, it's almost impossible to find them. And no bacteria is just as bad as a bacterial overgrowth, but I can't believe anything they say regarding bacteria in an old sample anyway. I always give probiotics to patients with diarrhea to help re-establish normal intestinal flora.

I hope you can get to the bottom of this soon. Diarrhea is no fun for your cat or for you.

To answer some questions- yes she tested postitive for the bacteria (sample taken at vet's office) and then a week later she tested negative (a sample brought from home that was abotu 15 minutes old when I brought it in) No idea what time they tested it that day though as they tested it after I left. They told me to bring in a sample from home and that it could be no more than an hour old (I live 15 minutes from the vet so as soon as I got the sample I took it there). She has been tested for Feline Leukemia (twice at my insistence) and both were negative. And she was also tested for FIV. She was wormed at 8 weeks old. The vet has not suggested anything to treat the diarrhea. THe next step he said would be a different antibiotic "in case we missed something". It is Metra-something. I didn't write it down. But they want me to pick it up and give it to her. I insisted that I make an appoinment for next week and bring her in (they told me to try the antibiotic for a week and then see if she improves) She does not appear to be dehydrated (she urinates several times a day) but this morning she vomitted twice which is a new symptom (she hasn't vomitted for a week and a half. Her diet has not changed at all so I am concerned. She is still eating and playing and seems to feel fine. But I don't think she should still have diarrhea if they say she has no bacteria in her system. None of my other cats have any symptoms.

There are many reasons that lead to diarrhea in your cat. In this case, I think maybe the antibiotics kill all bacteria within the cat’s intestinal tract including the friendly bacteria that keep your cat healthy. You can read this article for more information: http://diarrheaincats.net/can-antibiotics-cause-diarrhea-cats

You can also try some home remedy to treat cat diarrhea, this site may help: http://diarrheaincats.net/home-remedies-for-curing-feline-diarrhea

Here is a link that might be useful: Diarrhea in Cats