As stated briefly, bee propolis is a natural antibiotic, antifungal, antibacterial and antiviral.
In the past, I would also use a product like garlic juice. Since garlic juice is a little bit expensive, I used this product only when I need to. I used bee propolis in my cat's food when he had the broken leg and I applied some garlic juice topically. I put some of the garlic juice right over my cat's cut, where the stitches were, because garlic is absorbed through the skin. Thus, the garlic juice became a topical natural antibiotic.
During World War 1 though, the doctors and nurses used to stick raw garlic cloves into the wounds of soldiers to prevent gangrene. The garlic has natural antibiotic and antiseptic properties.
Please remember that garlic, like all members of the onion family, is said to be toxic to pets. While garlic may be safe in lower doses, it is questionable in larger doses. As a result, I prefer to not use garlic internally and I only use garlic juice externally in a situations such as my cat's broken leg.
Chinese herbal stores often have some Chinese herbs in capsules that have a natural antibiotic action. Also, some health food stores have products similar to this.
Some people give the homeopathic remedy known as Traumeel
because it stimulates the body's own natural healing ability which can then help fight infections.
While there are many other remedies to use, I personally use bee propolis the most. All I do is put a drop or two onto some meats chunk before feeding.
If you have a serious problem and want to use natural antibiotics, I would suggest contacting a holistic veterinarian to discover other natural antibiotics and how much to use.