The Bug Stops Here: Treating Resistant Staph Infections Holly Roberts, DVM, MS, DACVD Blue Pearl Veterinary Specialists San Antonio, TX

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1 The Bug Stops Here: Treating Resistant Staph Infections Holly Roberts, DVM, MS, DACVD Blue Pearl Veterinary Specialists San Antonio, TX 1. Staphylococcus bacteria a. Gram positive b. Opportunistic pathogens i. Found in healthy individuals c. Two groups i. Coagulase positive 1. Staph. pseudintermedius, aureus, schleiferi ssp coagulans ii. Coagulase negative 1. Staph. Epidermidis, xylosus, felis, sciuri 2. B-Lactam Antibiotics a. Gram positive bacteria i. Peptidoglycan layer 1. Important for ell wall structural integrity 2. Contain penicillin binding protein (PBP) 3. Can produce B-lactamase or penicillinase enzymes a. Penicillins need a B-lactamase inhibitor b. Beta Lactam Antibiotic i. Binds to PBP ii. Disrupts final step of cell wall synthesis iii. Bactericidal 3. Methicillin Resistance a. Carries MecA gene b. Oxacillin used on cultures c. Inherently resistant to all beta lactams d. MRSA MRSP! i. Human pathogen 1. Higher zoonotic risk ii. Different oxacillin breakpoint e. Risk factors i. Recent hospitalization ii. Chronic skin disease iii. +/- Antibiotic usage iv. +/- Immunosuppression 4. Clinical Signs of Pyoderma a. Primary lesions b. Papules c. Pustules d. Nodule e. Hemorrhagic bullae f. Secondary lesions g. Crust h. Epidermal collarette i. Draining tract j. Alopecia 5. Bacterial Pyoderma in the Skin a. Levels of infection i. Surface 1. Above epidermis 2. Erythema, alopecia, exudate

2 3. Examples of common locations affected: bulldog folds, interdigital, neck folds, axilla, perivulvar ii. Superficial 1. Within epidermis 2. Pustules, papules, crusts 3. Examples of common locations affected: head, dorsum, lateral sides, ventrum iii. Deep 1. Within dermis 2. Bullae, nodules, draining tracts 3. Examples of common locations affected: interdigital nodules, limbs 6. Diagnosing a Bacterial Pyoderma a. Cytology i. Easy & inexpensive ii. Confirms presence of bacteria b. When to culture i. History of 1. <50% improvement within 2 weeks of treatment 2. Development of new lesions during therapy 3. Presence of lesions after 6 weeks + cocci on cytology 4. Intracellular rods on cytology 5. Prior history of multidrug resistant pyoderma 6. *Previous hospitalization or antibiotic usage ii. Never wrong to culture! c. How to Obtain a Skin Culture i. Pustule 1. Lance and sample 2. No prep required ii. Crust/collarette 1. Left edge and swab underneath 2. No prep required iii. Papule 1. Puncture and sample 2. Prep required iv. Deep tissue 1. Punch biopsy and submit 2. Prep required d. How to Read A Culture Report i. Identify organism 1. Genus & species for Staph 2. True pathogen vs. opportunistic organism vs. contaminant ii. Oxacillin susceptible vs. resistant iii. Minimum inhibitory concentration 1. Cannot compare among different antibiotics 2. Based on systemic level of drug that reaches skin iv. Oral options available 1. Drugs that have ( ) are preferred 2. If not, then consider topical therapy 7. Treating Bacterial Pyoderma a. Topical i. Shampoos ii. Wipes iii. Sprays iv. Mousse v. Ointment/creams b. Systemic

3 i. Oral ii. Injectable c. Antibiotic Treatment Options i. Tier 1 1. Clindamycin or lincomycin 2. 1 st generation cephalosporins 3. cephalexin, Clavamox 4. TMS 5. +/- 3 rd generation cephalosporins* a. *can fall in tier 1 or 2 6. cefovecin, cefpodoxime ii. Tier 2 1. Doxycycline or minocycline 2. Chloramphenicol 3. Fluoroquinolones 4. Rifampin 5. Aminoglycosides iii. Tier 3** 1. Linezolid 2. Vancomycin a. **ethically should be reserved for human use d. Treatment based on level of infection i. Surface infection 1. Topicals 2. Treat until resolution 3. Typically, 1-4 weeks ii. Superficial bacterial pyoderma 1. Topical and/or systemic 2. Treat for 1 week past clinical resolution 3. Typically, 2-4 weeks iii. Deep bacterial pyoderma 1. Ideally systemic 2. Treat for 2 weeks past clinical resolution 3. Typically 4-8 weeks e. 8. Case #1 Wrigley a. 9-year-old MC West Highland White Terrier b. History i. 4 year history of seasonally (spring, summer) nonseasonal pruritus ii. Recurrent skin infections iii. Previously received Cytopoint & Apoquel 1. No longer working per owners iv. 6 week history of alopecia, erythema, papules, and crusting dermatitis with increased pruritus 1. Treated with 21 day course of Clavamox and 10 day course of ciprofloxacin 2. No improvement c. Exam: i. Multifocal areas of alopecia with erythema as well as popular to crusting dermatitis 1. Lateral sides, head, ventral neck, and front limbs d. DDX: i. Demodicosis ii. Infectious 1. Bacterial pyoderma 2. Fungal

4 iii. Allergic dermatitis e. Diagnostics i. Deep skin scrape 1. Negative for mites ii. Cytology from crusting cocci/oif iii. Fungal culture 1. Not performed iv. Bacterial culture 1. Swab from under crust f. Treatment i. Clindamycin 7.5mg/kg PO BID for 4 weeks ii. 3% chlorhexidine/climbazole shampoo twice weekly iii. Apoquel 0.51 mg/kg PO once daily g. Follow Up i. Papules and crusting resolved after 4 weeks with new hair growth ii. Partially responded to food trial using Royal Canin KO iii. Dx: Environmental atopic dermatitis & cutaneous adverse food reaction iv. Currently maintained on Royal Canin KO diet & Cytopoint every 4-6 weeks +/- Apoquel prn h. 9. Case #2 Dingo a. 3-year-old M/C Australian Cattle Dog b. History: i. 8 week history of alopecia and crusting on head, trunk, and limbs ii. Pruritus occurred after lesions iii. Previously treated with cefpodoxime for 21 days iv. No reported improvement c. Exam: i. Multifocal to coalescing alopecia with erythema and hyperpigmentation as well as adherent scaling to crusting ii. Face, ventrum, limbs d. DDX: i. Demodicosis ii. Infectious 1. Bacterial pyoderma 2. Fungal iii. Immune mediated/drug reaction iv. Allergic dermatitis e. Diagnostics i. Deep skin scrape 1. Negative for mites ii. Cytology from scaling 1. Negative for cocci iii. Punch biopsies 1. Fungal culture- negative 2. Histopathology- eosinophilic superficial perivascular dermatitis aka hypersensitivity iv. Bacterial culture f. Treatment i. Chloramphenicol 52mg/kg PO TID for 5 weeks ii. Douxo Chlorhexidine shampoo once weekly 1. Did not tolerate baths 2. Switched to Douxo Chlorhexidine Mousse once daily g. Follow up i. Pruritus remained despite resolution of infection

5 ii. Now undergoing a food trial for allergic workup 10. Case #3 Lucas a. 4-year-old M/Int GSD b. History: i. Three week history of skin lesions on the trunk, ventrum, limbs, paws, and scrotum 1. Previous history of similar lesions 3 months ago- resolved with abx & fluconazole ii. Lethargic iii. Painful on skin lesions iv. Mildly pruritic v. Working law enforcement dog in South Texas 1. Exposure to anything outdoors c. Exam: i. Multifocal ulcerative to crusting dermatitis on the lateral sides, elbows, ventrum, scrotum, and limbs ii. Interdigital draining tracts and hemorrhagic bullae d. DDX: i. Infectious 1. German Shepherd Deep Bacterial Pyoderma 2. Fungal ii. Immune mediated/drug reaction iii. Neoplastic e. Diagnostics i. Cytology cocci (some intracellular), 2+ neutrophils, 1+ macrophages/oif ii. Punch biopsies 1. Fungal culture- negative 2. Histopathology- severe chronic active, lymphoplasmacytic and neutrophilic dermatitis with folliculitis, furunculosis, and serocelluar crust with cocci a. Consistent with German Shepherd Dog Deep Pyoderma/ Furunculosis iii. Bacterial culture f. Initial treatment i. Chloramphenicol 50mg/kg PO TID ii. Douxo Chlorhexidine Shampoo 1. Twice weekly iii. 4 week recheck 1. 30% improved, but new lesions 2. Second culture g. Second round of treatment i. Douxo Chlorhexidine Shampoo 1. Twice weekly ii. Douxo Chlorhexidine Spray 1. Daily on non-bath days iii. Mupirocin ointment 1. Twice daily 2. Working on most severe regions first, then move on iv. 8 week recheck 1. 75% resolution of lesions 2. No new lesions 3. Back to work v. 12 week recheck and beyond % resolution a. Some scarring present

6 2. Diagnosed with environmental atopic dermatitis a. Treated with allergen-specific immunotherapy & prn Apoquel 11. Zoonosis a. Risk very low for MRSP/MRSS i. Higher for MRSA, but still uncommon 1. Typically, humans transfer to pets ii. Elderly, children, immunocompromised more likely to be infected b. Prevention i. In clinic 1. Wear gloves & lab coat 2. Disinfect once (if not twice) any contacted surfaces 3. Keep isolated from other patients 4. WASH HANDS ii. At home 1. WASH HANDS 2. Avoid contact with any lesions/wounds 3. Keep away from immunocompromised individuals 12. Colonization a. Staphylococcus found in nose, GI tract, mouth in healthy population i. 30% people ii. 50% dogs b. MRSP in healthy pets i. 4.5% in healthy dogs ii. 1.2% in healthy cats c. Pets with resistance do not always carry resistant strains i. When in doubt with recurrence, then culture