Dr. Alberto Martin Cordero received the degree of Doctor in Veterinary Medicine by the University of Guadalajara. He studied Veterinary Dermatology in the European School for Advanced Veterinary Studies, University of Luxembourg. He is a member of the American Academy of Veterinary Dermatology and a founder member of the Latin American Society of Veterinary Dermatology. Is an assistant professor in University of Guadalajara, Department of Veterinary Medicine. He has been a speaker in numerous conferences in Mexico, Latin America and Eastern Europe; and presented articles and clinical cases in Latin America, USA, and Europe. He has been a coordinator in videotoscopy wetlabs and dermatology workshops. He is the coordinator of the dermatology program in Leon Conference (CVDL), currently the second largest veterinary meeting in the world. Dr. Alberto has published articles and clinical cases national and international. He works in private practice and it is the owner of VETDERM: the first veterinary dermatology referral practice the west of Mexico. He has realized visits in the Animal Dermatology Clinics in Southern California and in the Ludwig Maximilian University in Munich and Colorado State University.
Bacterial pyoderma, is one of the most common conditions in veterinary dermatology; a high number of patients with several dermatosis present a secondary bacterial infection. Due to the multiple numbers of presentations and clinical signs related is strictly necessary to perform the correct diagnostic approach in order to rule out the different diagnosis that may resemble lesions of pyoderma.
The skin surface in animals and humans is colonized by bacteria that reside in the superficial epidermis and the infundibulum of the hair follicles. The most common etiologic agent of pyoderma, Staphylococcus pseudointermedius, can frequently isolated from oral, nasal, genital and anal mucocutaneous sites. Normally this sites are reservoirs for bacterial colonization and they may be transported by licking or grooming.
We need to differentiate the organisms found in the skin between resident organisms and transient organisms. Resident organism live as normal inhabitants and are part of the microbiota the puppies obtain from the dam in the neonatal period; this kind of organism become residents and the strain of Staphylococcus pseudointermedius persist through dog's life.
Transient organisms may be cultured from the skin but they lack of significance unless they become involved in a pathologic process as secondary invaders.
Another term we need to understand is colonization versus infection. Colonization means that a potential pathogen is living on the skin or in a lesion but its presence is not causing reaction to the host. However in infections we have a direct reaction from the host and this may be differentiated with the presence of degenerate neutrophils and phagocytosed bacteria. This differentiation may be the guideline of our therapeutic decisions in order to maintain a treatment topical, systemically or both.
There are different presentations for bacterial pyoderma regarding the depth of the lesions, affected region and appearance. The depth of the lesions is classified as surface bacterial infections, superficial bacterial infections and deep bacterial infections.
Surface bacterial infections include intertrigo, pyotraumatic folliculitis and pyotraumatic dermatitis. Intertrigo is a surface irritation and inflammation of the skin due to the rubbing or frictional trauma of the skin, mostly due to skin folds or flaps. Pyotraumatic folliculitis is a deep suppurative folliculitis and pyotraumatic dermatitis is a moist acute inflammatory process caused by trauma. This last dermatitis is one of the most common and underlying causes include allergies, joint pain or stress related conditions.
Superficial bacterial infections include impetigo, superficial bacterial folliculitis, mucocutaneous pyoderma and dermatophilosis. Impetigo is characterized for the appearance of non-follicular subcorneal pustules in sparsely haired areas of the skin. The most common affected site in the ventral abdomen and puppies before puberty are more susceptible. In some cases the lesions regress spontaneously but topical therapy may be enough to control it. Underlying causes of immunosuppression may be look, as viral infections and parasites.
Mucocutaneous pyoderma occurs in dogs and primarily affects the lips and premolar skin; etiology is unknown although some patients with atopic dermatitis may develop it. Crusting and ulcerations observed in mucocutaneous pyoderma may resemble autoimmune conditions. Treatment is a combination of topical therapy with systemic antibacterial therapy, severe cases may be treated 3 to 4 weeks.
Superficial bacterial pyoderma or superficial bacterial folliculitis is the most common bacterial infection present in dogs. Lesions may appear as different presentations leading sometimes to misdiagnosis due to their resemblance to other dermatosis. For example, superficial bacterial folliculitis in short coated breed may appear as "moth eaten" with patchy alopecia and lack of inflammation. In other breeds as English Bulldog patches of alopecia with marked hyperkeratosis is a common presentation of superficial bacterial folliculitis.
Characteristic lesions of superficial bacterial folliculitis include, erythema, inflammation, papules, pustules, epidermal collarette, hyperpigmentation and spreading pyoderma appearance. Some of the lesions before mentioned may show the evolution of bacterial infection; in this manner, lesions that may appear as papules may evolve into pustules and epidermal collarette. Pustules are difficult to find intact in some cases due to their fragile nature; however, they may be crucial in the diagnosis. Cytology of an intact pustule may help us to differentiate among similar dermatosis that may be easily mistaken as pyoderma.
Deep pyoderma can be classified as deep folliculitis, furunculosis and cellulitis. It normally starts as a surface or follicular infection of bacterial, fungal or parasitic origin. If a generalized distribution is present common diagnosis include demodicosis, generalized dermatophytosis, cutaneous drug reactions, endocrine abnormalities and immunosuppression.
With the inflammation of the follicle, rupture occurs causing inflammatory material, microorganisms to disseminate and create draining tracts.
Other clinical presentations of deep pyoderma has been recognized and they may be present limited to certain regions of the body; nasal folliculitis and furunculosis and muzzle folliculitis and furunculosis, pedal folliculitis and furunculosis; breed predisposition is documented on each of the presentations.
Acral lick dermatitis and pyotraumatic dermatitis may lead to folliculitis and furunculosis; causes were previously discussed from allergies to behavioral disorders.
In deep pyoderma, cytology is more useful taking samples for material squeezed from draining tracts, especially if they were intact to prevent secondary bacterial colonization. Intracellular bacteria within phagocytic cells and inflammatory cells is the common finding.
In diagnosis and treatment of pyoderma we may follow 5 steps:
Review of the clinical signs present
Identification of microorganisms
Classification of the pyoderma
Establishment of treatment
Identify underlying cause
Identification of bacteria is performed by cytology; although is only helpful to classify the type of organism present and it is not specific to determine the bacteria. Culture and sensitivity is the gold standard for bacterial identification; however, there are some guidelines we need to follow to avoid secondary contamination of the sample.
Bacterial culture must be performed if therapeutic failure occur, especially if the treatment is focused on cytology findings. Sensitivity results must be interpreted carefully.
Samples for culture and sensitivity must be taken from sites with the less contamination possible and preferably from close tracts or pustules, lesions beneath the crust have potentially less secondary contamination. Even following these guidelines it is common to find transient microorganisms on the result.
The results of the culture should always be interpreted according to cytology findings. The most common species isolated in canine pyoderma is S. pseudintermedius. Finding other staphylococci is not uncommon, but their significance varies depending on species. The other coagulase-positive staphylococci, S. aureus and S. schleiferi coagulans, should be considered pathogenic.
Most bacterial infections in dogs have an underlying condition present; in order to prevent recurrence identifying the underlying cause is mandatory. In this matter we need to differentiate between recurrent or resistance pyoderma.
There are several conditions easily mistaken as pyoderma; however, performing a correct diagnostic approach will minimize the risk of misdiagnose.
Among this conditions we can mention the following:
Immunomodulatory responsive lymphocytic plasmacytic pododermatitis
Pemphigus foliaceus (pemphigus complex)
Subcorneal pustular dermatosis
Superficial pustular drugs reaction
Sterile eosinophilic pustulosis
Nasal eosinophilic folliculitis and furunculosis
Linear IgA pustular dermatosis
Bacterial Resistance: Dealing with Tough Cases
Bacterial resistance is an emerging conditions. The most common resistant organism in veterinary dermatology is the Methicillin resistant Staphylococcus pseudointermedius MRSP. The first report occurred in North America in 1999 and since then several reports have been publish in different parts of the globe. In the author experience, Latin America is experiencing an increase of MRSP in the same rate that has been appearing around the world.
Overuse of antimicrobial agents, interrupted treatments, repetitive treatments especially in recurrent pyoderma, incorrect dose are the most common factors for presentation of MRSP.
The term methicillin resistant has been used to describe organism resistant to beta lactamases; although methicillin is no longer used in bacterial cultures the term prevailed; oxacillin has replaced methicillin on culture and sensitivity tests. MRSP have the mecA gene expression that allows to create PBP2a (penicillin binding protein 2a) which avoid beta lactamases to adhere to the staphylococci preventing death. Normally MRSP are resistant only to penicillins and beta lactamic antibiotics; however there are some organism multi drug resistant to quinolones, aminoglycosides, among others.
In the cases before described, use of topical therapy should be the best choice, and it may be used as daily basis or three to four times a week. Chlorhexidine is among the best therapeutic agents; bleach dilution has been anecdotally reported as useful in the topical treatment of MRSP; although there is no establish dose.
The most effective measure to prevent recurrence is to identify and control the underlying primary disease. Protocols for the use of systemic antimicrobials to aid in the prevention of pyoderma, or to delay recurrence, have been published and advocated in public prior to the widespread emergence of MRSP and have included pulse therapy (intermittent administration of therapeutic doses of antimicrobial drugs) and continuous use of subtherapeutic dosing. However, there is significant concern for the selection of resistance with these protocols. Accordingly, their use is strongly discouraged.
There is evidence of prevalence of MRSP in patients over 6 months and the author have seen patients with a prevalence longer than 4 years, avoiding systemic antibiotics and practice good hygiene are good tools in preventing prevalence of MRSP on affected patients.
1. Hillier A, Lloyd DH, Weese JS, Blondeau JM, Boothe D, Breitschwerdt E, et al. Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis (Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases). Vet Dermatol. 2014. doi:10.1111/vde.12118.
2. Frank LA, Loeffler A. Meticillin-resistant Staphylococcus pseudintermedius: clinical challenge and treatment options. Vet Dermatol. 2012;23(4), 283–e56. doi:10.1111/j.1365-3164.2012.01047.x.
3. Gortel K. Recognizing pyoderma. Vet Clin North Am Small Anim Pract. 2013;43(1):1–18. doi:10.1016/j.cvsm.2012.09.004.
4. Beck KM, Waisglass SE, Dick HLN, Weese JS. Prevalence of meticillin- resistant Staphylococcus pseudintermedius (MRSP) from skin and carriage sites of dogs after treatment of their meticillin-resistant or meticillin-sensitive staphylococcal pyoderma. Vet Dermatol. 2012;23(4):369–e67. doi:10.1111/j.1365-3164.2012.01035.x.
5. Miller WE, Griffin CE, Campbell KL. Muller & Kirk's Small Animal Dermatology. 7th edition. 2012:184–200.