Page 1523 - Clinical Small Animal Internal Medicine

1461

VetBooks.ir

166

Bacterial Pyodermas
Jennifer R. Schissler, DVM, MS, DACVD

College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA

Etiology/Pathophysiology Pyoderma Classifications
and Presentations
Pyodermas are bacterial infections of the skin and com-
monly involve coagulase‐positive staphylococci. Indeed, Pyodermas are often categorized based on the depth of
staphylococcal pyoderma is one of the most common infection (surface, superficial or deep) and the site
conditions treated in clinical practice. For this reason, involved, particularly when describing a pyoderma
this chapter is focused exclusively on staphylococcal that affects a specific body region (e.g., interdigital
pyodermas. Staphylococcal infection opportunistically pyoderma, nasal pyoderma). These categorizations are
arises secondary to dermatologic or systemic diseases useful, particularly the depth of infection because
that prompt cutaneous physical or immunologic func- it dictates the methods and duration of therapeutic
tion insults. These may include hypersensitivity, endo- interventions.
crine, conformational, and keratinization disorders, as
well as an immunocompromised status. Clinical presen- Surface Pyodermas
tations are diverse, and mimic a multitude of other
dermatopathies. In the current era of antimicrobial Acute Moist Dermatitis
resistance, optimal outcomes for staphylococcal pyo- Acute moist dermatitis, also known as pyotraumatic der-
derma are achieved via correct diagnosis, rational treat- matitis and commonly referred to as a “hot spot,” is charac-
ment and follow‐up, and management of the inciting terized by the rapid development of a focal, erythematous,
cause(s). erosive, and exudative lesion that develops due to intense
Staphylococcus pseudintermedius, previously identi- pruritus and self‐trauma (Figure 166.1).
fied as Staphylococcus intermedius, is the most common Acute moist dermatitis is typically initiated by hyper-
etiologic agent in canine pyoderma. Staphylococcus sensitivity disorders, including cutaneous adverse food
aureus, Staphylococcus schleiferi subsp. coagulans, and reaction, atopic dermatitis, and flea bite hypersensitivity,
coagulase‐negative staphylococci such as Staphylococcus or pruritogenic parasitic diseases such as pediculosis,
schleiferi subsp. schleiferi are isolated at a lesser fre- sarcoptic mange, and cheyletiellosis. Surface staphylo-
quency on healthy or inflamed skin. coccal overgrowth is concurrently present in nearly all
Staphylococcal pyoderma is less prevalent in cats cases of acute moist dermatitis. Cytology of exudate
than dogs. Feline keratinocyte adhesion of S. aureus obtained via surface impression smear reveals neutro-
and S. pseudintermedius is inferior compared to human phils and intracellular and extracellular cocci. Superficial
and dog keratinocytes, perhaps a reflection of inferior bacterial folliculitis lesions (see “Superficial bacterial fol-
host adaptation. S. pseudintermedius, S. schleiferi, and liculitis” section below) observed at the periphery of the
S. aureus are most frequently isolated; S. aureus is iso- self‐trauma suggest a longer duration of staphylococcal
lated at a higher frequency than in dogs. involvement and that the staphylococcal folliculitis itself

Clinical Small Animal Internal Medicine Volume II, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical