---start---- derm 10/30 note: some handouts were given out in class, others are in your mailboxes. byrne: bacterial skin diseases most common comment from junior students: all the skin lesions look the same. well, that's kind of true b/c all it can do is lose hair, change color, get scaly, crusted, nodular, eroded, or ulcerated. you have to look at what is going on and try to associate it with signs and history. in some systems like renal system, you can look more at lab data. but here we really need a good history to make a good diagnosis. so. bacterial skin diseases: -host vs organism -staphylococcal pyoderma -forms of s.p. -other bacterial skin infections we're going to talk about asso'ns b/w bacteria and host, mostly wrt staph, but also applicable to other organisms. host vs organism: -protective barrier = skin: stratum corneum if intact is best infection fighting attribute of skin. haircoat also protects skin, some components of sebum inhibit colonization by pathogenic bacteria, normal flora help too. skin also sloughs routinely, old cells peel off, new cells move outward, so it is hard to infect the skin since it keeps falling off. also skin has its own immune system cells that we've talked about before. physical factors: these are important. if we do not know the cause is seasonal, the hard and fast rule is there is no seasonality to bacteriall infections. however temperature and humidity play a role, so maybe we see more when it's warmer or more humid. breeds with redundant skin, or skin defects, may be prone to certain infections. also seborrhea may change microenvironment, poor grooming may create favorable growth environment. dog skin pH is relatively neutral which may be why they get more skin infxn than other spp. dogs tend to not have sebum plugs at each follicle, so that might also predispose them. disease factors: seborrhea, atopy, dermatoses in general. some diseases predispose to skin infections by making skinn more hospitable to bacteria. deleterious host respose - sometimes there is an exaggerated respose - superantigen respose, IgE, mast cell degranulation. some animals are hypersensitive to staph, they get big inflammatory responses, making skin more easily infected. resident bacteria vs transient bacteria - residents can survive and proliferate on normal skin; transient ones can't multiply on the skin. colonization: potential pathogen present but nont producing a reaction in the host. infection: pathogen is present and causing a host reaction. staphylococcus intermedius: coagulase positive, relatively heat resistant and tolerant to antiseptics. has some virulence factors which promote pathogenicity - slime production, protein A, lipotechoic acid, peptidoglycan, coagulase. these promote adherence and invasion. also some exotoxins known to be in staph aureus in people have also been seen in staph intermedius in dogs. can be fairly pathogenic but probably what is more important is the host response. staphylococcal pyoderma: primary infections: occur inn otherwise healthy skin; not a major problem. antibiotics cure these. they do not recur and are less common than secondary infections. these are not so important. secondary infections: more important, recurrent infections. these have an underlying cause and are much more common tha primary infections. most common 4 basic underlying causes: -allergic -seborrheic -endocrine/metabolic -follicular disorders idiopathic recurring pyoderma: whatever the underlying cause is, it isn't one of the above and we can't find out what it is. we assume host immunodeficiency but don't know. could be some kind of complement problem, lymphocyte problem - not sure. could be hypersensitivity to staph antigens altering epidermal permeability. how to tell causes apart: allergy: pruritus remains after the pyoderma resolves. not always true, but often true. allergic dogs are prone to infection because of: theories include self trauma, corticosteroids (CCS), increased epidermal permeability, and increased bacterial adhesion with atopy. seborrheic disorders: idiopathic cocker seborrhea, other. these dogs have inborn stratum corneum defect. follicular plugging/comedome/blackhead formation may play a role,. increased numbers of bacteria on skinn may lead to pruritus, too. endocrine/metabolic dz: may cause immunosuppression or direct skin effect - Cushings dz dogs have thin skin, poorer barrier, more comedomes, so increased infections. also hypothyroidism, sex hormone changes, diabetes, hyperlipidemic disorders, and of course malnutrition. follicular disorders: -demodecosis: some of the worst pyodermas are inn these dogs -dermatophytosis is sometimes a problem only if very severe -feline acne -follicular dysplasia -schnuzer comedone syndrome: a follicular plugging disorder -sebaceous adenitis diagnostic techniques: if you suspect pyoderma, how do you prove it without waasting time and money on diagnostics? this will depend on history. if there is no history of infection, don't recommend big workups. if it is recurring, look for a cause. first, prove it is a pyoderma though: -cytology/impression smears: intact pustules ruptured, crusts lifted off, draining tracts, whatever. stain with modified Wright's or gram stain. -supportive findings: phagocytized cocci, degenerate neutrophils, ideally both but degen neutrophils alone are enough to support your dx. -culture and sensitivity: pustules broken open and swabbed, crusts lifted off and swabbed, non draininng abscess disinfected and lanced - all of this with no sterile prep. if you need a punch biopsy and culture, you do use a sterile prep. some bacterial infections do not cause papules or pustules and you have to just submit a chunk of skin - that's when you'd need a sterile prep (usually just an alcohol swab.) skin biopsy/histopathology: we will sometimes use this to confirm a diagnosis in a chronic case not responding to treatment. this can help to confirm an underlying cause or figure out what's really going on. pyodermas stick out obviously on biopsy - anyone can dx it. sometimes if there is extra inflammation it can interfere with your dx - overwhelming neutrophilic infiltration may cover everything up. slide: severe pododermatitis - biopsy not that useful b/c it is just all neutrophils. topical therapy: benefits: removes debris, reduces/eliminates bacterial population on skin, encourages drainage, removes inflammatory cells, pus, etc. [slide] chlorhexiderm products. topical tx more commonly used in conjuction with systemic abx. hydrotherapy is excellent for crusty lesions; clipping long haired animals is required for deep draining lesions and studies of hotspots in long haired dogs showed clipping really helped. shampoos: chlorhexidine and benzoyl peroxide are most effective for pyodermas. ethyl lactate is expensive povidone triclosan brands not so important Allerderm, Oxydex, etc. topical antibiotics: we do like to use some of these. two most common are mupirocin (bactoderm) and neomycin which actually is fairly effective topically although it can sensitize some patients. also erythromycin, clindamycin can be used in some cases, some people like them for feline acne though they may irritate some individuals. most cases we see require systemic antibiotics. how do you know if you need that or not? those that are superficial or deep need them, those that are just on the surface do not. the thing about skin is that drug levels are less than that in serum/blood. so you have to consider dose carefully. some drugs require higher doses. only 40% of blood flow reaches the dermo/epidermal junction. abscesses have poor perfusion, exudate can block diffusion of drug, and keratin is a big problem with deep pyodermas b/c of foreign body reaction. effective drugs for staph in dogs: lincomycin and erythromycin are "first line of defense" although erythromycin can cause vomiting. clindamycin is fairly good but expensive. good for anaerobes too, though. potentiated sulfas - avoid in dobes chloramphenicol - not used so much anymore clavulanated amoxicillin - good drug but really expensive (clavamox) enrofloxacin (baytril) - less expensive but ?? efficacy oxacillin/dicloxacillin - expensive cephalosporin clients want meds that are easy to give. something they can hide in food will be given more easily. some of these drugs need to be given on an empty stomach so that's not so good. also they want to give it once or twice a day, not three or four times a day. always consider compliance things that do not work: penicillin ampicillin tetracycline streptomycin principles of effective therapy: choose the right drug and give for adequate period of time. we frequently see animals that have been undertreated. -dosage and interval for antibiotics -for superficial infection minimum duration is 21 days ** during this 21 days, we'd like to see visible lesions resolve. this could be on the exam. ask owners when lesions went away. if lesions went away on the 21st day, give 7 more days of meds. another problem is use of steroids. these are to be avoided. steroids decrease the immune response and allow infection to continue. also sometimes owners will stop giving the antibiotic when the skin starts to look better and then the infection isn't really gone. mixed infections: choose drug effective for *staph* and that should work. exception: severe deep pyoderma with pseudomonas in an immunocompromised dog the most commonn cause of an inability to resolve skin infection or for relapse days after tx is *insufficient duration of therapy* for previously untreated infections, drug selection may be empirical culture and sensitivity isn't cost effective for those cases. but if infection is recurring, or you have a really big dog and it will cost a lot to treat, a culture and sensitivity is a good idea. so, long term therapy, large breed dog, poor response to prior therapy, history of relapse, history of adverse drug reactions, or known mixed infection - these are all good indications for culture and sensitivity. idiopathic recurring pyoderma: -underlying disease indeterminate -attempts to control pyoderma fail -unmanaged allergy or endocrine disease outweighs benefit of immunomodulation -immunomodulation is used in dogs with immunodeficiency principles of immunomodulators: -goal is to prevent or decrease frequency of infection recurrences -do not kill bacteria, do not resolve existing infections -start concurrently with an antibiotic -eventually continue immunomodulator alone immunomodulators: -staphage lysate (SPL): lysed human staph aureus. may improve CMI, non specific and humoral immunity. they are trying out a staph intermedius bacterin, too, that might work better. SPL used 0.5 ml SQ twice/week x 10 wk, then decrease frequency. can caue injection site swelling, less often fever, malaise -autogenous staph bacterins: made from cultures taken from the patient's skin. need experienced microbiologist. uses the specific strain causing the pyoderma. use like SPL; may cause more injection site swelling, animal may develop sensitivity to product. -immunoregulin: from human proprionobacterium acnes. this organism is a pretty good immunostimulant. used IV only, 2 x weekly for 2 weeks, once weekly, then as needed. insufficient informtion on longterm use. longterm abx therapy: drugs with wide margin of safety cephalosporins, oxacillin, dicloxacillin, clavamox recurrent episode basis, or longterm treatment basically an attempt to decrease frequency of infections; not that often used. recurrent episodic abx method: have owner keep supply, treat specific episodes and give for 14 days longer than clinical signs are present. longterm treatment method: pulse therapy - week on, one to three weeks off suboptimal dose - daily dose at low level, lowest effective dose/frequency luckily, s.intermedius doesn't get resistant as quickly as s.aureus. Forms of staph pyoderma: specific types the way infections are broken down is by location: surface, superficial, deep. surface pyoderma: acute moist dermatitis - hotspot - rapidly developing, many traumatic etiologies (dog chewing itself, etc). dx: history, PE, scrapings. exudate, alopecia, some crusting may be seen. describing lesions: describe hair, alopecic or not, then lesion - raised, papule, pustule, etc - then color, then modifiers for exudate. this is alopecic, squamous, erythematous lesion with purulent exudate. to manage this, correct the predisoposing factor - flea hypersensitivity or whatever. clip and clean the lesion +/- sedation as needed. topical therapy such as mild astringent or abx, E-collar, antipruritic therapy. if you have a true surface pyoderm, you may give 10 days of oral pred on taperinng dose. but if you see signs of follicular infection, avoid the steroids. (he said avoid antibiotics but didn't mean that) intertrigo: a skin fold dermatitis. type of surface pyoderma. think shar pei :). moisture, warmth, friction of folds on each other. dx: signalment, PE. can have malassezia component (yeast). r/o demodex. management usually mostly client education - ower has to clean and control exudate with mild astringents or whatever, drying powder, etc. decrease moisture, lose wt if fat dog, surgical correction if you can't manage it. mucocutaneous pyoderma - lips and perioral skin affected. mechanisms involved here are really a bit different from typicaal pyoderma. most common in GSD but can affect any age, breed, sex. it does not originate at lip folds. it occurs at non-haired skin of lip junction. area gets edematous, thick, inflamed, depigmented. usually not too uncomfortable. [slide] here we see demarcations of lesions - two pink areas in normal black lip skin. [slide] GSD with depigmentation of lip margins; he also has lesions below the philtrum on his upper lip area. ddx: zinc responsive dermatosis, discoid lupus, pemphigus, drug eruption. dx on history and PE - scrapings to rule out demodex, try treating with abx and if no response, biopsy to rule out other ddx. this is fairly amenable to therapy. systemic abx x 3-4 weeks are usually effective. topicals not that useful since on lips - sometimes longterm topicals are used to prevent recurrence depending onn location of lesion. food allergy may play role in etiology, not sure. on the exam, some questions will be multiple choice, there will be a lot of case scenario type things - history, pe, choose a test, or know the test, choose a therapy, etc. case study: 6 mo old spayed english bulldog "brown stains on face" noticed 2-3 weeks ago, no change since no therapy tried yet PE: erythema, hypotryichosis within facial skin fold, brown materia staining hair in the fold. no epiphora or conjunctival abnormalities present dx: facial fold dermatitis of some sort what test do you do? impression smear will tell you what is there in terms of organism/process - would find degenerative neutrophils and some cocci. since there is hair loss, do a skin scraaping for demodex. that is negative. so dx intertrigo. discuss cleaning, use of astringents, possibly topical abx. tx: topical mupirocin BID x 3 wks, Domeboro solution as needed, owner observe folds daily superficial pyodermas: superficial dz almost always affects hair follicle at some point. these affect all epidermal layers, form papules/pustules, and more distal part of hair follicle. you usually see little pustules with hairs sticking out of them. -impetigo: disease of sparsely haired skin. little pustules on young dogs, puppies, perhaps related to stress, poor diet, parasites, viruses. another problem esp in older dogs is Cushing's dz. those dogs are older, with huge pustules on abdomen, usully. that's called "bullous impetigo". if you see these in an older dog look for cushings, other immunosuppression. PE: small superficial pustules, no involvement of hair follicles, usually on glabrous skin or sparsely haired skin (inguinal area) dx: history, PE, cytology management: health management in young dogs, topical or systemic therapy, look for immunosuppressive dz in older dog. -superficial bacterial foliculitis: main form of staph pyoderma ** follicular disease. lesions very variable. follicular pustules quickly crust over. can progress to deep pyoderma. depending on underlying cause, may be pruritic. on glabrous /less haired skin, we see papules, pustules with protruding hair shafts, and collarettes. old lesions may be hyperpigmented. on the dorsum of short haired animals: disheveled, bumpy fur; hairs pushed up by papules, motheaten appearance, alopecia. people sometimes think it is hives. [slide] dachshund with motheaten appearance - multifocal areas affected. this looks like staph. other two big ddx would be demodex and dermatophytosis. dermtophytosis would almost always also be on part of head/face. but you'd have to do skin scraping to r/o demodex. sometimes in short coated dogs you can see the lesions better by looking from the tail end toward the head. some dogs have lesions on glabrous skin - papular, crusted, clustered plaque type, then also on haired skin, small alopecic areas with less erythema.both are staph. dogs with long hair tend to get bigger lesions - large areas of alopecia, erythema and papules at periphery - "superficial spreading pyoderma" - epidermal collarettes are common in these longhaired dogs. the lesions can get big - 4-5 inches across. again, ddx demodex, dermatophytosis, other pustular diseases such as autoimmune dz. dx made by cytology, c & s, biopsy, scrapings, fungal exam. management of recurring case - if not pruritic, look for endocrine/metabolic cause. if pruritic, think atopy, FAD, food allergy (95% of these are pruritic, but some are not, so it is hard to dx sometimes.) case: 4 yr old female scottie 2 year hx of itchiness and sores infection responds to steroids and abx eliminateion diet trial with lamb and rice diet failed currently on "pills for itching" PE: hypotrichosis, pustules, etc dx: what do you do? skin scraping and impression smears we find bacteria with no demodecosis. dog is pruritic. suppose we tx with abx and she is still pruritic. what causes do you consider? atopy, food allergy. pustule cytology: degenerate neutrophils, cocci skin cytology: cocci scraping: NSF tx: clavamox, chlorhexidine shampoos, antihistamine REAL diet trial started - but didn't help. intradermal allergy test - multiple allergies - dx atopy improved with hyposensitization and courses of abx and topicals -schnauzer comedone syndrome - another superficial pyoderma Deep pyoderma: this is down deep into the follicle. also accompanied by furunculosis - rupture of follicle, big inflammatory response to keratin. factors that favor deep pyoderma: demodecosis, dermatophytosis, trauma/foreign body, other. On PE, we see more on pressure points. alopecia is more variable. fistulae and firm skin are common. superficial lesions arae also seen. typically ulceration, swelling, and edema are most typical. ddx for cellulitis and panniculitis: SLE, systemic mycosis, other dx: seaarch for demodex, cytology, bacterial/fungal culture, biopsy in severe cases. pyotraumatic folicullitis: acute moist dermtitis and deep folliculitis. necrotizing folliculitis, furunculosis. any breed esp golden, st bernard, newfie. sometimes precipitated by acute pruritogenic event. often on cheek, side of neck. need to clip to visualize well. dx: history, PE, cytology management: avoid steroids. systemic therpay, topical therapy, shave lesions. muzzle folliculitis and furunculosis: common in young short coated dog like dalmation, dobe, great dane. may be due to friction and breaking of hairshafts. alopecia, erythema, exudationn, some sort of bluish, bullous, hemorrhagic. massive inflammation, organisms present. PE: alopecic follucular papules, etc. management: treat infection, avoid behavior that traumatizes skin (offer different toy or whatever), systemic abx or topicals or both. topical corticosteroid may be useful in the future. frequent cleaning. ----end---