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Bacterial Skin Infections . Basic Dermatology Curriculum . Last updated August 10, 2011. Module Instructions. - PowerPoint PPT Presentation

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Bacterial Skin Infections Last updated August 10, 20111Basic Dermatology Curriculum 1Module InstructionsThe following module contains a number of blue, underlined terms which are hyperlinked to the dermatology glossary, an illustrated guide to clinical dermatology and dermatopathology.We encourage the learner to read all the hyperlinked information.

2Goals and ObjectivesThe purpose of this module is to help medical students develop a clinical approach to the evaluation and initial management of patients presenting with cutaneous bacterial infections.By completing this module, the learner will be able to:Describe the morphology of common cutaneous bacterial infectionsDiscuss the bacterial etiologies of cellulitis and erysipelasRecognize clinical patterns and risk factors that suggest MRSARecommend initial steps for the evaluation and treatment of common cutaneous bacterial infectionsRecognize characteristic features of necrotizing fasciitis and the need for emergent treatment, including surgical intervention

33Case OneMr. Neal Tolson44Case One: HistoryHPI: Mr. Tolson is a 55-year-old man who presents with 5 days of worsening right lower extremity pain and a red rash. He reports recent fevers and chills since he returned from a camping trip last week. PMH: arthritisMedications: occasional NSAIDs, multivitaminAllergies: no known drug allergiesFamily history: father with history of melanomaSocial history: lives in the city with his wife, two grown childrenHealth-related behaviors: no alcohol, tobacco or drug useROS: able to bear weight, no itching55Vital signs: T 100.4, HR 90, BP 120/70, RR 14, O2 sat 97% on RASkin: erythematous plaque with ill-defined borders over the right medial malleolus. Lesion is tender to palpation. With lymphatic streaking (not shown).Tender, slightly enlarged right inguinal lymph nodes (not shown)Laboratory data: Wbc 12,000 (75% neutrophils, 10% bands), Hct 44, Plts 335

Case One: Exam

66Case One, Question 1What is the most likely diagnosis?Bacterial folliculitisCellulitisNecrotizing fasciitisStasis dermatitisTinea corporis

77Case One, Question 1Answer: bWhat is the most likely diagnosis?Bacterial folliculitis (Would expect pustules and papules centered on hair follicles. Without systemic signs of infection)CellulitisNecrotizing fasciitis (Would expect rapidly expanding rash, usually appears as a dusky, edematous, red plaque. In this setting, it is always appropriate to ask the question, Could this be necrotizing fasciitis?)Stasis dermatitis (Although found in similar location, stasis dermatitis often presents with pruritus and scale, which may erode or crust. Without fever or elevated wbc)Tinea corporis (Would expect annular plaque with elevated border and central clearing. Painless, without fever or elevated wbc)

88Diagnosis: CellulitisCellulitis is a very common infection occurring in up to 3% of people per year Results from an infection of the dermis that often begins with a portal of entry that is usually a wound or fungal infection (e.g., tinea pedis)Presents as a spreading erythematous, non-fluctuant tender plaqueMore commonly found on the lower legStreaks of lymphangitis may spread from the area to the draining lymph nodes

99Cellulitis: Risk FactorsRisk factors for cellulitis include:Local trauma (bug bites, laceration, abrasion, puncture wound)Underlying skin lesion (furuncle, ulcer)Inflammation (local dermatitis, radiation therapy)Edema and impaired lymphatics in the affected areaPreexisting skin infection (impetigo, tinea pedis)Secondary cellulitis from blood-borne spread of infection, or from direct spread of subjacent infections (fistula from osteomyelitis) is rare10Cellulitis: Etiology80% of cases are caused by gram positive organismsGroup A streptococcus and Staphylococcus aureus are the most common causal pathogensThink of other organisms if there have been unusual exposures:Pasteurella multocida (animal bites)Eikenella corrodens (human bites)

11Case One, Question 2What is the next best step in management?Apply topical antibioticsApply topical steroids, compression wraps, and encourage leg elevationBegin antibiotics immediately with coverage for gram positive bacteriaOrder an imaging study

1212Case One, Question 2Answer: cWhat is the next best step in management?Apply topical antibiotics (not effective)Apply topical steroids, compression wraps, and encourage leg elevation (this is the treatment for stasis dermatitis, not cellulitis)Begin antibiotics immediately with coverage for gram positive bacteria Order an imaging study (radiographic examination is not necessary for routine evaluation of patients with cellulitis)1313Cellulitis: TreatmentIt is important to recognize and treat cellulitis early as untreated cellulitis may lead to sepsis and deathMay use the following guidelines for empiric antibiotic therapy:For outpatients with nonpurulent cellulitis: empirically treat for -hemolytic streptococci (group A streptococcus)Some clinicians choose an agent that is also effective against S. aureusFor outpatients with purulent cellulitis (purulent drainage or exudate in the absence of a drainable abscess): empirically treat for community-associated MRSAFor unusual exposures: cover for additional bacterial species likely to be involved1414Cellulitis: Treatment (cont.)Monitor patients closely and revise therapy if there is a poor response to initial treatmentElevation of the involved areaTreat tinea pedis if presentFor hospitalized patients: empiric therapy for MRSA should be consideredCultures from abscesses and other purulent skin and soft tissue infections (SSTIs) are recommended in patients treated with antibiotic therapy1515MRSA Risk FactorsAntibiotic useProlonged hospitalizationSurgical site infectionIntensive careHemodialysisMRSA colonizationProximity to others with MRSA colonization or infectionSkin traumaCosmetic body shavingCongregated facilitiesSharing equipment that is not cleaned or laundered between users

Healthcare-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA) risk factors include:1616Antibiotics Used to Treat MRSADrugDosage (adult dosing with normal renal function)CommentsClindamycin

600 mg/kg IV Q8H300-450 mg PO TIDExcellent tissue and abscess penetration.Risk for C. difficileInducible resistance in MRSATrimethoprim-Sulfamethoxazole (TMP/SMX)1 or 2 double-strength tablets PO BIDUnreliable for S. pyogenes (will need to combine with amoxicillin to cover for group A strep)Doxycyline100 mg PO BIDUnreliable for S. pyogenes (will need to combine with amoxicillin to cover for group A strep). Do not use in children < 8 years old.Linezolid600 mg IV Q12H600 mg PO BIDExpensive. No cross-resistance with other antibiotic classesVancomycin1g IV Q12HParenteral drug of choice for treatment of infections caused by MRSA1717Case Two, Question 1Does this person have cellulitis?

18

18Yes- a type of cellulitis called Erysipelas

1919ErysipelasErysipelas is a superficial cellulitis with marked dermal lymphatic involvement (causing the skin to be edematous or raised)Main pathogen is group A streptococcus Usually affects the lower extremities and the facePresents with pain, superficial erythema, and plaque-like edema with a sharply defined margin to normal tissue Plaques may develop overlying blisters (bullae)May be associated with a high white count (>20,000/mcL)May be preceded by chills, fever, headache, vomiting, and joint pain2020Example of ErysipelasLarge, shiny erythematous plaque with sharply demarcated borders located on the leg21

21Case Two, Question 2What is the most appropriate treatment?Oral antibioticsOral steroids Topical antibioticsTopical moisturizersTopical steroids

2222Case Two, Question 2Answer: aWhat is the most appropriate treatment?Oral antibioticsOral steroids Topical antibioticsTopical moisturizersTopical steroids

Oral antibiotics are the most appropriate therapy in uncomplicated erysipelas. 23Erysipelas: TreatmentImmediate empiric antibiotic therapy should be started (cover most common pathogen - Streptococcus)Monitor patients closely and revise therapy if there is a poor response to initial treatmentElevation of the involved areaTreat tinea pedis if present

24Case ThreeMr. Jesse Hammel2525Case Three: HistoryHPI: Mr. Hammel is a 27-year-old man with a history of skin popping (subcutaneous or intradermal injection of drug) who presents to the emergency department with a painful, enlarging mass on his right arm for the last two days. PMH: History of skin and soft tissue infections, hospitalized with MRSA bacteremia two years agoMedications: noneAllergies: no known drug allergiesFamily history: father with diabetes, mother with hypertensionSocial history: lives with friends in an apartment, works in retailHealth-related behaviors: IVDU (intravenous drug use), including skin popping. No tobacco or alcohol use. ROS: no fevers, sweats or chills2626Case Three: Skin ExamErythematous, warm, fluctuant nodule with several small pustules throughout the surfaceVery tender to palpation

2727Diagnosis: AbscessA skin abscess is a collection of pus within the dermis and deeper skin tissuesPresent as painful, tender, fluctuant and erythematous nodules Often surmounted by a pustule and surrounded by a rim of erythematous edemaSpontaneous drainage of purulent material may occur28Case Three, Question 1What is the next best step in management?Incision and drainageTopical antibioticsOffer HIV testa and ba and c

2929Case Three, Question 1Answer: eWhat is the next best step in management?Incision and drainage (incision and drainage is the treatment of choice for abscesses)Topical antibiotics (not effective)Offer HIV test (patients with risk factors for HIV should be offered an HIV test, e.g. IVDU in this patient)a and ba and c

30Abscess: TreatmentAbscesses require incision