Antibiotics are used to fight bacteria and fungus in and on the body. Bacteria are classified according to their ability to cause disease. Pathogenic bacteria are capable of producing a particular illness or infection. Nonpathogenic bacteria live on or within the host but do not cause illness under normal conditions. These bacteria are called normal flora. Some actually produce substances necessary to the well-being of the host. For example, bacteria in the bowel synthesize vitamin K, which is necessary for blood clotting. Rarely, nonpathogenic bacteria will overgrow and cause symptoms due to their sheer numbers.
Antibiotics fall into two categories: Bacteriostatic and fungistatic drugs inhibit the growth of microorganisms but don’t kill them; bactericidal and fungicidal drugs destroy the microorganisms outright.
Rarely diagnosed in cats but one of the most common conditions affecting dogs, mange is a skin disease caused by several species of tiny mites. Some mange mites are normal residents of a cat’s skin and hair follicles, while others are considered parasites. All mites can cause mild to severe skin infections if they proliferate.
Antibiotics are specific for certain bacteria. So, one antibiotic will not be effective against all infections. The large number of antibiotics now available brings with it new possibilities for cats to develop sensitivities and allergies to specific drugs and multiplies the potential hazards of administration.
Antibiotics alter the normal flora that serves as a protective barrier against pathogens. When these normal, beneficial organisms are killed off, harmful bacteria are free to multiply and cause disease. The best example is severe diarrhea that follows the use of certain antibiotics, which change the normal flora of the bowel.
Certain antibiotics can affect the growth and development of unborn or newborn kittens. Tetracycline and griseofulvin are two examples. They should not be used in pregnant queens.
Antibiotics and Steroids
Steroids are often combined with antibiotics, particularly in topical preparations for the eyes and ears, and on the skin. Corticosteroids have anti-inflammatory effects. By reducing swelling, redness, and tenderness, they often give the impression that the cat is getting better when actually, he is not.
Steroids have one other side effect that is undesirable: They depress the normal immune response. This can impair the cat’s ability to fight the infection. Antibiotic medications that contain steroids should be used only under the guidance of a veterinarian. This is particularly true for eye preparations.