View source for Skin and soft tissue infections (SSTI) (IDSA 2014)

= Skin and soft tissue infections (IDSA 2014) =

== Introduction ==

* Exposure history is important
* Physical examination for diagnosis
* History must include
** Immune status
** Geographic locales
** Travel history
** Recent trauma and surgeries
** Recent antibiotics exposure
** Lifestyle
** Hobbies
** Animal exposures

[Management pathway for cellulitis](SSTIs 2014-1.pdf)

== Impetigo and Ecthyma ==

=== Background ===

* Impetigo is a superficial infection of the epidermis (?)
* Bullous impetigo is caused by Staph. aureus strains that produce a toxin that cleaves the dermal-epidermal junction
* Non-bullous impetigo can be caused by Staph. aureus and Group A ''Strep''
* Ecthyma is a deeper infection, and heals with scarring

=== Organisms ===

* ''Staph aureus''
* Group A ''Strep''

=== Management ===

* Gram stain and culture of any pus, if possible
* Superficial and localized infections can be treated with topical mupirocin BID x5d
* Otherwise, treat with dicloxacillin or cephalexin x7d
* Can narrow if cultures grow Group A ''Strep'' alone
* If MRSA, treat with doxycycline, clindamycin, or Septra

== Purulent SSTIs ==

* Includes abscesses, furuncles, carbuncles, and inflamed epidermoid cysts

=== Abscesses and inflamed epidermoid cysts ===

* Epidermoid cysts contain skin flora in keratinous material and are not necessarily infected, but can become inflamed if the capsule ruptures
* Organisms: ''Staph. aureus'' and skin flora
* Management
** Incision and drainage; no packing (increases pain without changing outcomes)
** Add antibiotics if impaired immunity or systemic symptoms

=== Furuncles and carbuncles ===

* Furuncles are small abscesses of hair follicles
* Carbuncles involve many adjacent follicles
* Organisms: almost exclusively ''Staph. aureus''
* Management
** Often drain spontaneously with warm wet compresses
** If large enough, can incise and drain
** No need for antibiotics unless systemic symptoms

=== Recurrent abscesses (at the same site) ===

* Differential diagnosis includes foreign body, hidradenitis suppuritiva, and pilonidal cysts
* Organisms: excluding above causes, often ''Staph. aureus''
* Management
** Treat underlying cause, if possible
** Can try MRSA decolonization with
*** Intranasal mupirocin BID for 5 days each month, with daily chlorhexadine washes
*** Clindamycin 150mg for 3 months
* If present since childhood, rule out a neutrophil disorder

== Erysipelas and Cellulitis ==

=== Background ===

* Infections of the dermis and subcutaneous fat, characterized by diffuse areas of erythema, edema, and tenderness
* Specifically *not *purulent; if there's an abscess, then it's an abscess with surrounding erythema (not with surrounding cellulitis)
* Erysipelas refers to either (1) a superficial infection of the upper dermis, or (2) a cellulitis of the face, or (3) a synonym of cellulitis
* On examination, there can also be lymphangitis, peau d'orange, vesicles, bullae, or hemorrhagic lesions
* Occasionally, the fever can precede the skin findings
* Risk factors include: obesity, trauma, surgery, prior cellulitis, venous insufficiency, lymphedema

=== Organisms ===

* Group A ''Strep''
* Other streptococci
* ''Staph. aureus''

=== Management ===

* Blood cultures are unnecessary unless there is something unusual, immunosuppression, or sepsis
* Treat with an antistreptococcal antibiotic, such as penicillin, amoxicillin, dicloxacillin, cephalexin, or clindamycin for 5 days
* No need to empirically cover MRSA
* Treat any underlying skin breach, including macerated skin between the toes
* Can use prednisone (if no diabetes) or NSAIDs to help symptoms resolve faster

==== Recurrent infections ====

* Identify and treat predisponsing conditions: edema, obesity, eczema, venous insufficiency, and toe web abnormalities
* Prophylactic antibiotics can be considered in patients who have 3-4 episodes per year despite treating their predisposing factors
** Oral penicillin or sythromycin bid for 4 to 52 weeks
** IM benzathine penicillin every 2-4 weeks
* Continue prophylaxis until the predisposing factors resolve

== Surgical site infections ==

=== Background ===

* Three classes
** ''Superficial incisional SSI:'' involve only the subcutaneous space, occurs within 30 days, and has one of:
*** Purulent drainage
*** Positive culture of aseptically-obtained fluid or tissue
*** Local cellulitis after the wound has been opened
*** Expert opinion suggests SSI
** Deep incisional SSI: involves fascia and mucle, within 30 days (or 1 year if prosthesis inserted), and same as above
** Organ/space SSI: same as deep SSI but may involve organs and deep space, e.g. peritonitis, empyema, and joint infections

=== Organisms ===

* Depends in part on site of incision, but generally ''S. aureus'' and streptococcal species
* Axillary incisions may have more gram-negative organisms, and paerineal incisions have more gram-negatives and anaerobes

=== Management ===

* Open the incision and evacuate the cavity
* Drainage alone if &lt;5cm erythema and minimal systemic symptoms
* For some reason, IDSA seems to suggests tazo or mero as first-line; possibly just for gastrointestinal and genitourinary incisions

== Necrotizing Fasciitis ==

=== Background ===

* Involve the fascial or muscle compartments and are life-threatening
* Usually develop from initial skin trauma, which can be trivial including insect bites
* Presents as a rapidly-progressing cellulitis, with systemic symptoms and pain out of proportion to findings
* May have wooden-hard induration, and if there is an open wound, you can easily dissect the fascial planes
* Risk factors include diabetes

=== Organisms ===

* Monomicrobial: S. pyogenes, S. aureus, V. vulnificans, A. hydrophila, and anaerobic streptococci (Cutibacterium)
* Polymicrobial: numerous aerobes and anaerobes, mostly arising from the bowel or genitourinary tract

=== Management ===

* CT or MRI is not diagnostic
* Surgical exploration for diagnosis and deep tissue cultures
* Surgical intervention urgently, and daily until source control is achieved
* Treat with antibiotics until source control achieved and afebrile for 48-72 hours
* Empiric antibiotics should cover gram-positives, gram-negatives, and anaerobes
* Group A streptococcal toxic shock syndrome should be treated with clindamycin and penicillin
** The utility of IVIg is unclear; small RCT suggests not

=== Fournier gangrene ===

* Variant involving the scrotum and penis or vulva, where a perianal or retroperitoneal infection has spread to the genitalia
* Testes, glans, and spermatic cord are typically spared
* Mostly mixed aerobes and anaerobes

== Pyomyositis ==

=== Background ===

* Pus within an individual muscle group, often associated with tropical climates
* Risk factors include tropical climates, HIV, diabetes
* May have a firm woody feel
* CK often normal

=== Organisms ===

* ''Staph. aureus'' in 90%
* Group A Strep and gram-negative enterics also possible

=== Investigations ===

* MRI establishes the diagnosis, though CT and US are useful
* Get blood cultures (positive in 5-30%)
* Repeat imaging if persistently bacteremic in order to find other infections

=== Management ===

* Needs incision and drainage
* Vancomycin is appropriate empiric therapy
* Add Gram-negative coverage if immunocompromised or open trauma
* Cefazolin for oxacillin for MSSA
* Duration is with IV until better and not bacteremic, then oral to complete 2-3 weeks

== Gas Gangrene and Myonecrosis ==

=== Background ===

* Increasing pain at the injury site within 24 hours
* Skin starts pale, then bronze, then purplish-red, tenderness at the site, followed by reddish-blue bullae
* Septic

=== Organisms ===

* ''Clostridium perfringens'', ''C. novyi'', ''C. histolyticum'', and ''C. septicum''
* ''C. perfringens'' most commonly associated with trauma-associated gangrene, and ''C. septicum'' with spontaneous gangrene in neutropenic patients or those with GI malignancy

=== Management ===

* Many organisms produce gas, so needs broad empiric coverage with pip/tazo, amp/sulb, or carbapenem
* Penicillin + clindamycin is the recommended treatment
* Unclear role for hyperbaric oxygen

== Animal Bites ==

=== Prophylaxis ===

* Unclear benefit of prophylaxis, but suggest 3-5 days of amox/clav to cover aerobes and anaerobes in high-risk patients
** Immunocompromised
** Asplenic
** Advanced liver disease
** Preexisting edema in the affected area
** Moderate to severe injuries, especially hand or face
** Injuries that penetrate the periosteum or joint capsule
* Should be assessed for rabies prophylaxis
* Avoid primary wound closure except on the face, in which case it should be done with copious irrigation

=== Wound infections ===

* Purulent wounds are often polymicrobial, and need to cover aerobes and anaerobes
* Nonpurulent wounds are often monomicrobial with staphylococci and streptococci, but are also sometimes polymicrobial
* ''Pasteurella'' is common in both
* Antibiotic options
** Amox/clav is good empiric coverage
** 2nd and 3rd gen cephalosporins +/- clinda/metronidazole
** Carbapenems
** Moxifloxacin
** Doxycycline
** Septra + clinda/metronidazole
** Levfloxacin + clinda/metronidazole
* Human bites also include streptococci, ''S. aureus'', ''Eikonella corrodens'', ''Fusobacterium'', ''Peptostreptococcus'', ''Prevotella'', and ''Porphyromonas''
** ''Eikonella'' is resistant to 1st-gen cephalosporins but amox/clav is good as is moxifloxacin

=== Tetanus toxoid ===

* Give tetanus toxoid vaccine if not vaccinated within 10 years
* Tdap preferred to Td, if they haven't previously received it

== Cutaneous Anthrax ==

=== Background ===

* Incubation period 1-12 days followed by pruritis, then papule, then vesicles, the finally painless ulcer with black eschar without pus
* Eschar sloughs after 12-14 days
* Surrounding edema can be minimal or severe and lymphadenopathy is common
* Often mild systemic symptoms
* Diagnosis
** Vesicles: unroof and soak 2 dry swabs in the vesicular fluid
** Ulcer: 2 moist swabs in the ulcer base or along the eschar edge
** Punch biopsy for immunohistochemistry or PCR

=== Management ===

* Oral penicillin V 500 mg qid x7-10 days
* If bioterrorism/aerosol exposure, ciprofloxacin 500 mg po bid or levofloxacin 500 mg poVI daily for 60 days

== Bacillary Angiomatosis and Cat Scratch Disease ==

=== Background ===

==== Cat scratch disease ====

* Caused by ''Bartonella henselae''
* After an incubation period of 3-30 days following a scratch or bite, a papule or pustule forms
* Lymphadenopathy develops at about 3 weeks, and resolveds within 1-6 months
* Occasionally, nodes can drain; rarely, extranodal visceral disease can occur

==== Bacillary angiomatosis ====

* Caused by ''Bartonella henselae'' or ''B. quintana'' in immunocompromised patients, especially those with AIDS
* Can appear either as red papular that vary in size (millimeter to centimeters) and number (1 to 1000), or as subcutaneous, painful nodules with overlying normal or dusky skin

=== Diagnosis ===

* Fastidious, difficult-to-grow
* Serology cross-reacts between ''B. henselae'' and ''B. quintana''
* PCR is one option

=== Management ===

==== Cat scratch disease ====

* If &gt;45 kg: azithromycin 500 mg on day 1 then 250 mg daily for 4 more days
* If &lt;45 kg: azithromycin 10 mg/kg on day 1 then 5 mg/kg daily for 4 more days

==== Bacillary angiomatosis ====

* Erythromycin 500 mg qid or doxycycline 100 mg bid for 2 weeks to 2 months

== Erysipeloid ==

=== Background ===

* Cutaneous infection caused by ''Erysipelothrix rhusiopathiae'', a thin, pleomorphic, non-spore-forming Gram-positive rod
* Acquired by handling fish, marine animals, swine, or poulty
* Incubation period of 1 to 7 days, followed by red maculopapular lesion on fingers or hands, spreading centrifugally with central clearing
* May have a blue ring with peripheral red halo (target appearance)
* Lymphadenopathy is common, though systemic symptoms are not
* Diagnosed by aspirate and culture

=== Management ===

* Penicillin 500 mg qid or amoxicillin 500 mg tid for 7 to 10 days
* ALternatives include cephalosporins, clindamycin, and fluoroquinolones
* Resistant to vancomycin, teicoplanin, and daptomycin

== Glanders ==

* Caused by ''Burkholderia mallei'', an aerobic Gram-negative rod
* Acquired from horses and mules through skin contact or inhalation
* Causes ulcerating nodular lesions of the skin and mucosa
* Treated with ceftazidime, gentamicin, imipenem, doxycycline, or ciprofloxacin for a prolonged course (?6 months)

== Bubonic Plague ==

* Caused by ''Yersinia pestis'', a facultative anaerobic Gram-negative coccobacillus
* Acquired from rodents
* Three syndromes:
** Bubonic
*** Most common and classic, acquired from infected fleas or through breached skin
*** Incubation period of 2 to 6 days followed by fever, headache, chills, and regional lymphadenopathy
*** Skin lesion sometimes present at site of entry
*** May progress to septicemia and secondary pneumonia
** Septicemic
** Pneumonic
*** Transmissible human-to-human
* Diagnosis made by blood culture, lymph node aspirate, or PCR; serology may be helpful for confirming the diagnosis retrospectively
* Treatment
** Streptomycin 15 mg/kg bid for 10 to 14 days
** Alternatives: genatmicin, tetracycline, chloramphenicol, maybe fluoroquinolones
** If pneumonic form develops, needs to be in droplet isolation until 48 hours of effective therapy

== Tularemia ==

* Gram-negative coccobacillus ''Francisella tularensis''
* Distinct syndromes:
** Ulceroglandular
** Glandular
** Typhoidal
** Pneumonic
** Oculoglandular
** Oropharyngeal
* Acquired by handling infected animals, by tick bites, sometimes by animal bites (especially cats), as well as by biting flies or mosquitoes
* Skin ulcer forms at site of bite after 3-10 days with tender adenopathy, fevers, headache, and malaise (ulceroglandular syndrome)
* If the ulcer heals quickly, with ongoing symptoms, they may present without the ulcer as glandular syndrome
* Diagnosis
** Serology
** Culture with cysteine-supplemented media; notify the lab first
** PCR may be useful
* Treatment
** Streptomycin 15 mg/kg/day q12h (max 2 g per day)
** Gentamicin 1.5 mg/kg q8h (or 2 mg/kg q8h in children)
** Duration 7-10 days, 14 days if severe
** Fluoroquinolones, tetracycline, or doxycycline can be used in mild to moderate cases, for a total of 14 days for oral therapy
** Inherent resistance to beta-lactams
* High rate of relapse

== Immunocompromised Patients ==

* Infections may appear different or less pronounced due to the damped host immune response
* Differential diagnoss should include
** Infectious: bacterial, fungal, viral, and parasitic infections
** Non-infectious: drug eruption, cutaneous infiltration of malignancy, chemotherapy reactions, radiation reactions, Sweet syndrome, erythema multiforme, leukocytoclastic vasculitis, and graft-vs-host disease
* Biopsy or aspiration should be implemented early

=== Cancer Patients with Febrile Neutropenia ===

* Early aspiration or biopsy for etiology
* Risk stratify with MASCC score
* Investigate with blood cultures, CXR +/- chest CT

==== Ecthyma gangrenosum ====

* A cutaneous vasculitis caused by invasion of the vessel wall media and adventitia by bacteria
* Presents as painless erythematous papules that progress to pain and necrosis within 24 hours
* Usually lower extremity
* Caused by ''Pseudomonas aeruginosa'', but also other Gram-negatives, some Gram-positives, and fungi, even HSV

==== Management ====

* Vancomycin plus antipseudomonal antibiotics
* Duration for most SSTIs is 7 to 14 days
* Surgical intervention for source control, if appropriate
* G-CSF is not routinely recommended
* Acyclovir if disseminated HSV or VZV is suspected

==== Persistent or recurrent ====

* Consider yeasts and molds, so need to add empiric antifungals
** ''Candida'' spp. should be treated with an echinocandin
*** ''C. parapsilosis'' should be treated with amphotericin
*** Fluconazole is acceptable if sensitive
*** Duration is two weeks
** ''Aspergillus'' spp. should be treated with voriconazole or amphotericin, posaconazole, or echinocandin
*** Duration is 6 to 12 weeks
** Mucor/Rhizopus should be treated with amphotericin or posaconazole +/- an echinocandin
** ''Fusarium'' should be treated with high-dose voriconazole or posaconazole
* Ensure resistant bacteria are covered as well, with MRSA coverage and other broad-spectrum
* Add acyclovir if HSV or VZV is suspected; PCR from blood may be helpful
* Blood cultures and skin biopsy, aspiration, or culture is recommended for diagnosis
* Galactomannan is unhelpful in patients on antifungals

=== Cellular Immunodeficiency ===

* Lymphoma, leukemia, HSCT or SOT recipients, steroid use, other immunosuppressive agents
* Consult a dermatologist, consider biopsy
* Empiric antibiotcs, antifungals, and/or antivirals in life-threatening situations

==== Nontuberculous Mycobacteria ====

* Mostly occurs at site of innoculation but can have hematogenous dissemination
* Most common in SOT is cutaneous and pleuropulmonary disease
* Most common in HSCT is cather-related infections and bacteremias
* ''Mycobacterium avium'' complex occurs in HIV disease
* Non-HIV species include: ''M. fortuitum'', ''M. chelonae'', ''M. abscessus'', ''M. ulcerans'', ''M. kansasii'', ''M. haemophilum'', ''M. marinum'', ''M. mucogenicum''
* Skin infections can include a poorly-resolving cellulitis, painless 1 to 2 cm nodules, necrotic ulcers, and subcutaneous abscesses
* Treatment is with combination antibiotics for 6 to 12 weeks
** Macrolide plus second agent that it is susceptible
** See [https://doi.org/10.1164/rccm.200604-571ST ATS/IDSA Guidelines 2007]

==== Nocardia ====

* Cutaneous ''Nocardia'' is usually metastatic from a primary pulmonary infection
* Species include ''N. farcinica'', ''N. brasiliensis'', and others
* Skin involvement is usually subcutaneous nodules, abscesses, and panniculitis, often cold and painless
* Septra for 6 to 24 months, though combination therapy should be considered in severe infections
* Debride necrotic nodules and large abscesses

==== Fungi ====

* Most common causes of cutaneous infection include ''Aspergillus'', ''Mucormycosis'', ''Scedosporium'', and ''Fusarium''
* Can present as papules, nodules, ulcers, and ecthyma gangrenosum
* Skin biopsy is helpful in diagnosis
* Voriconazole good for ''Aspergillus'', ''Scedosporium'', and ''Fusarium''
* Cryptococcal infections usually involve lungs, with hematogenous spreading
** Papules, nodules, pustules, chronic draining necrotic ulcers, or cellulitis
** Fluconazole for milder infections
* Disseminated histoplasmosis is rare and is treated with amphotericin for 1 to 2 weeks followed by itraconazole for 6 to 12 months

==== Viruses ====

* VZV is common, sometimes disseminated
** Dermatomal pain often preceeds the lesions by 24- to 72 hours
** Duration of disease usually 2 weeks, but may progress slower in immunodeficient patients
** Treated with high-dose IV acyclovir
** Suspect resistance if it develops while on prophylaxis
* HSV also common
** Orofacial and genital sites most common, but can autoinnoculate any area
** Often preceded by local pain or tingling
** Disseminated disease is rare and usually associated with HSV-2
** Acyclovir, famciclovir, and valacyclovir are all options
** Foscarnet needed in cases of resistance

==== Parasites ====

* ''Strongyloides stercoralis'', amebae (''Acanthamoeba'' and ''Balamuthia''), ''Trypanosoma cruzi'', and ''Sarcoptes scabiei'' (Norwegian scabies)