Clostridium intestinal infection....???

Essentially they can get gut bacteria from darned near anywhere -- including, but not limited to, drinking out of a puddle or licking your shoe or some grass. 

Now, all those things (stress, etc.) set the gut up to not deal as well with that bacteria -- it can be anything from one incident of something overwhelming to a whole cluster of things all "stressing a bit more" or adding a bit more bacteria. 

 this is not a cop out ... but seriously sometimes it just "happens".  That doesn't sound scientific but it's simply a normal name for a whole chain of events that all conspires against them.

 That IS one of the reasons why I tend to have fecals for my dogs far more often than most folks -- 3 of my 4 tend to be immune-suppressed so they can be sitting targets.  *sigh*

Clostridium is a genus (group) of 100+ species of anaerobic bacteria (bacteria that thrive in the absence of oxygen).  A couple within that genus are among the bacteria that cause basic food poisoning.  Do you know which particular species - Clostridium perfringens, Clostridium botulinum, Clostridium difficile, etc., that your dog has?

Here are some sites that may help you understand a bit about this genus:

• http://www.peteducation.com/article.cfm?c=2+1677&aid=2407
• http://en.wikipedia.org/wiki/Clostridium
• http://www.medterms.com/script/main/art.asp?articlekey=6539
• http://www.textbookofbacteriology.net/clostridia.html

As soon as your dog can keep anything down, I suggest feeding a good probiotic.  Basically you help to defeat the bad bacteria by flooding the system with good bacteria.  If your dog is on antibiotics, give the probiotic 3-4 hours after giving the antibiotic.  Antibiotics kill the good bacteria as well as the bad, so you have to keep giving the probiotics.

Stomach acids (especially those of a dog) are designed to kill bacteria.  In this situation I suggest getting an enteric-coated probiotic to get more of the bacteria into the intestine alive.  Such coatings protect the probiotics from stomach acids and dissolve in the intestine where the probiotics are needed.  Health food store personnel should be able to help you pick a product.

Examples:

• Enzymatic Therapy's Probiotic Pearls
• Nature's Way Primadophilus Bifidus
• Multidophilus 12 from Solaray
• Jarro-Dophilus EPS from Jarrow Formulas

My pick would be the Probiotic Pearls.  I believe the Enzymatic Therapy enteric-coating to be superior to that of competitors.

 Are you feeding a raw diet?  Sometimes, they pick it up from meat.  Therapy dogs have been known to pick up Clostridium difficile on their paws as they travel through hospitals or nursing homes ( all you therapy dogs, bring paw wipes!).