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.
The following information isn’t intended to replace regular visits to your veterinarian. If you think your cat may have feline infectious peritonitis, please see your veterinarian immediately. And remember, please do not give any medication to your pet without talking to your veterinarian first.
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
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
Why Antibiotics Fail
Antibiotics may not always be effective, for a number of reasons.
Inadequate Wound Care
Antibiotics enter the bloodstream and are carried to the source of the
infection. Abscesses, wounds that contain devitalized tissue, and wounds with
foreign bodies (dirt or splinters, for example) are resistant areas. Under such
circumstances, antibiotics can’t penetrate the wound completely. Accordingly,
it is essential to drain abscesses, clean dirty wounds, and remove foreign
An antibiotic chosen to treat an infection must be effective against the
specific bacteria that is infecting the body. The best way to determine
susceptibility is to sample the organism, grow it on a culture plate, and
identify it by the way its colony appears and by microscopic characteristics.
Antibiotic discs are then applied to the culture plate to see which discs
inhibit the growth of bacteria colonies. The results are graded according to
whether the bacteria is sensitive, indifferent, or insensitive to the effects
of the antibiotic. Laboratory findings, however, do not always coincide with
results in the patient. Nonetheless, sensitivity testing is the best way to
select the most effective antibiotic.