The optimal duration of therapy required to effectively treat AMP is unknown. Despite the fact that some cats with AMP have
demonstrated lasting complete remissions after just a few weeks of antibiotic therapy1,8 and that spontaneous remissions from cutaneous, atypical mycobacterial infections occur frequently in people,7 current recommendations suggest that cats demonstrating an initial positive response to antibiotic monotherapy receive three
to six months of continuous treatment.1 Another therapeutic regimen advocates that therapy be continued for one month beyond the resolution of all clinical signs.1 As some cases of AMP can be associated with disease that historically waxes and wanes, prolonged therapy is designed to
eliminate clinically dormant organisms, and some cats require indefinite maintenance therapy to maintain remission.1,7,11 Bathing with antimicrobial shampoo and using Elizabethan collars and analgesics may improve a cat's appearance and quality
of life, but they do not seem to substantially affect the disease's clinical course. Do not give affected cats immunosuppressive
agents, such as corticosteroids.
Surgical treatment
Surgery is an often effective but primarily adjunctive (used when single modality treatment fails to resolve clinical disease)
tool for feline AMP. Surgically excising affected tissues without administering appropriate antimicrobial therapy is doomed
to failure. Preoperative and perioperative antimicrobials are advocated to reduce the microbial burden before surgery and
to ensure eradication of any residual mycobacteria. Surgery should be considered and potentially incorporated into the therapeutic
plan in cats with AMP if 1) the cutaneous disease burden is extensive, 2) one or more locally confined, large lesions are
severe or hinder the patient's mobility, or 3) clinical progress has become static after initial improvement with medical
treatment.
Chronic wounds in cats pose a formidable challenge to veterinary surgeons. These chronically affected or infected cats may
have both nonhealing wounds and nodular or ulcerative lesions. In the veterinary literature, the role of surgery in treating
chronic skin lesions in cats is controversial and depends on the nature and extent of the lesion. It is important to remember
that chronic wounds in cats are associated with myriad infectious agents, such as mycobacteria, L-form bacteria, and feline
cowpox, just to list a few. Other causes such as primary immunodeficiency, hyperadrenocorticism, neoplasia, foreign body reaction,
and drug reaction must also be considered and ruled out before surgical intervention is considered.
2. The immediate postoperative appearance of the caudal ventral abdomen of a cat with a chronic draining skin lesion due
to AMP. Aggressive radical excision must be performed to remove all affected tissue.
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The timing of surgery depends directly on the size and extent of the lesions. Patients with lesions that can be easily excised
and closed are excellent candidates for early surgical intervention. The rationale for early surgical intervention is twofold:
1) to obtain adequate surgical margins and, therefore, serve as a possible curative procedure, and 2) to obtain adequate tissue
samples for histologic examination, bacterial culture and antimicrobial sensitivity testing, and special staining procedures.
It is vital to obtain adequate surgical margins in all dimensions. In our experience, in cases in which lesions are on the
flank or abdomen, complete surgical excision must include removing body wall. We have found that less aggressive attempts
at resection have poor results and usually necessitate a second, more aggressive surgery. We have found that in most cases,
closing the body wall can be performed without serious complications (Figure 2). Lesions on the thorax may necessitate the removal of all underlying muscle and fascia to the level of the ribs.
3. An intraoperative photo showing the use of omentum (arrowheads) to enhance healing in the cat shown in Figure 1.
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Extensive lesions that would be difficult to close after surgery should first be treated medically. Multiple skin biopsy samples
for histologic examination, bacterial culture and antimicrobial sensitivity testing, and special staining can be obtained
at this time, followed by four to six weeks of appropriate antibiotic therapy. The patient should then be evaluated to determine
whether surgical excision is possible. If surgical excision can be performed, wide surgical margins must be obtained as previously
mentioned, and antibiotic therapy must be continued for a minimum of four weeks.
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