Treatment of Superficial Bacterial Folliculitis

Treatment of Superficial Bacterial Folliculitis

Andrew Hillier, Columbus, Ohio

Superficial bacterial folliculitis (SBF) is diagnosed frequently in dogs and can develop secondary to almost any primary skin disease. SBF is most commonly encountered as a complication of primary allergic, parasitic, or metabolic disease. Staphylococci, and in particular Staphylococcus pseudintermedius, are the most important pathogens causing SBF (see Chapter 100).

Diagnosis

Clinical Lesions

Common lesions of SBF are papules and pustules, typically arising from a hair follicle. Pustules, which may be transient, are usually small but may on occasion be large, expansile, or flaccid. Crusts and variable alopecia, hypopigmentation and hyperpigmentation, and erythema may be present. Epidermal collarettes and target lesions can be prominent lesions in some patients.

Cytologic Analysis

Cytologic demonstration of cocci is helpful if there is any doubt that lesions represent SBF. However, if classic lesions of SBF are present and if similar lesions have responded to antimicrobial drug (AMD) therapy in the past, then cytologic examination is unnecessary. Cytologic analysis for cocci is never a poor diagnostic test and is mandatory in the following circumstances:

• When typical lesions are not present.

• When typical lesions are present but there has been a poor response to AMDs.

• When bacterial culture is performed (in the case of a negative culture result, a positive cytologic finding would prompt repeated culture, whereas a negative culture and negative cytologic finding would suggest a sterile pustular disease for which biopsy may be indicated).

The absence of bacteria on cytologic analysis does not rule out SBF, and the absence of inflammatory cells does not rule out infection (these cells may be absent in the presence of immunosuppressive diseases or in patients treated with immunosuppressive drugs).

Bacterial Culture and Susceptibility Testing

When to Culture

Bacterial culture is never contraindicated. Culture of SBF lesions is mandatory in the following circumstances:

• When there is less than 50% improvement in lesions after 2 weeks of systemic antibiotic therapy.

• When new lesions emerge 2 weeks or more after the initiation of systemic AMD therapy.

• When residual lesions remain after 6 weeks of AMD treatment.

• If there is a prior history of multidrug-resistant infection in the patient or in a pet from the same household.

What to Culture

Pustules are the preferred lesion because they have the highest reported rate for positive growth. Performing a diligent search, clipping hair with scissors to obtain “windows of the skin,” and using a magnifying lens are encouraged. Do NOT disinfect the pustule surface. Lance the lesion with a sterile needle and apply a culturette to the purulent exudate.

Crusts, especially if fresh with pus on the underneath surface, are also suitable lesions to culture. Do NOT disinfect the surface; lift the edge of the crust with a sterile needle or forceps and touch a culturette to the exposed skin surface.

Epidermal collarettes may be cultured, but this is not as sensitive a technique as pustule culture. Do NOT disinfect; rub a culturette across the center of the lesion and under the leading edge of the collarettes.

Finally, papules also may be cultured; however, the technique is more invasive, time consuming, and expensive. After subcutaneous injection of local anesthesia, wipe the lesion once with 70% alcohol, then collect a tissue sample with a 3-mm sterile punch and submit the sample in a sterile container. Suture the biopsy site.

Antimicrobial Susceptibility Testing

The following AMDs should be tested with all staphylococcal isolates: erythromycin, clindamycin, tetracycline (doxycycline), trimethoprim/sulfamethoxazole, gentamicin, cephalothin (cefazolin), cefpodoxime, cefovecin, cefoxitin, amoxicillin/clavulanic acid, oxacillin (methicillin), enrofloxacin, and marbofloxacin. With the emergence of multidrug-resistant staphylococcal infections as a significant problem in recent years, it is mandatory that all clinical microbiology laboratories test for methicillin resistance using the correct guidelines for assessment of S. pseudintermedius as mandated by the Clinical and Laboratory Standards Institute.

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Jul 18, 2016 | Posted by admin in PHARMACOLOGY, TOXICOLOGY & THERAPEUTICS | Comments Off

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