Cellulitis Treatment & Management

Updated: Aug 24, 2018
  • Author: Thomas E Herchline, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Treatment

Approach Considerations

Antibiotic regimens are effective in more than 90% of patients. However, all but the smallest of abscesses require drainage for resolution, regardless of the microbiology of the infection. In many instances, if the abscess is relatively isolated, with little surrounding tissue involvement, drainage may suffice without the need for antibiotics.

Note that management of cellulitis may be complicated because of the emergence of methicillin-resistant Staphylococcus aureus (MRSA) and macrolide- or erythromycin-resistant Streptococcus pyogenes. [2] Nonsevere cases of cellulitis may be treated empirically with semisynthetic penicillins, first- or second-generation oral cephalosporins, macrolides, or clindamycin.

Unfortunately, for patients with cellulitis surrounding abscess formation, 50% of MRSA strains also have inducible or constitutive clindamycin resistance. [2] Of the strains of S pyogenes resistant to macrolides, 99.5% seem to remain susceptible to clindamycin and 100% to penicillin. [2] Most community-acquired MRSA infections (CA-MRSA) are apparently susceptible to trimethoprim-sulfamethoxazole and tetracycline.

In 2011, the IDSA published updated guidelines regarding management of MRSA in adults and children, and in 2012, the updated IDSA guidelines for the Diagnosis and Treatment of Diabetic Foot Infections were published. [67, 68] Readers are encouraged to check the IDSA guidelines Web site for the 2014 updated recommendations for the diagnosis and management of skin and soft-tissue infections. [2]

Consider consulting an infectious disease specialist if the patient is not improving with standard treatment or if an unusual organism is identified; a critical care specialist for patients who are systemically ill and require admission to a critical care unit; or an ophthalmologist in cases of orbital cellulitis.

Cellulitis without draining or abscess

In cases of cellulitis without draining wounds or abscess, streptococci continue to be the likely etiology, [2] and beta-lactam antibiotics are appropriate therapy, as noted in the following:

  • In mild cases of cellulitis treated on an outpatient basis, dicloxacillin, amoxicillin, and cephalexin are all reasonable choices

  • Clindamycin or a macrolide (clarithromycin or azithromycin) are reasonable alternatives in patients who are allergic to penicillin

  • Levofloxacin may also represent an alternative, but the prevalence of resistant strains has increased, and fluoroquinolones are best reserved for gram-negative organisms with sensitivity demonstrated by culture [8, 2]

  • Some clinicians prefer an initial dose of parenteral antibiotic with a long half-life (eg, ceftriaxone followed by an oral agent)

Recurrent cellulitis

In the occasional patient with recurrent disease usually related to venous or lymphatic obstruction, the cellulitis is most often due to Streptococcus species, and penicillin G or amoxicillin (250 mg bid) or erythromycin (250 mg qd or bid) may be effective. [13] If tinea pedis is suspected to be the predisposing cause, treat with topical or systemic antifungals.

In a randomized, controlled trial in 274 patients who had experienced 2 or more episodes of cellulitis of the leg, a 12-month course of low-dose penicillin helped prevent recurrent cellulitis. The median time to first cellulitis recurrence was 626 days in the patients receiving penicillin (250 mg twice daily), versus 532 days in the placebo group. During the prophylaxis phase, 22% of the penicillin group (30 of 136 participants) had a recurrence, as compared to 37% of the placebo group (51 of 138 participants). However, the protective effect progressively diminished once the drug therapy ceased. [69, 70]

Severe cellulitis

Patients with severe cellulitis require parenteral therapy, such as the following:

  • Usually, cellulitis is presumed to be due to staphylococci or streptococci infection and may be treated with cefazolin, cefuroxime, ceftriaxone, nafcillin, or oxacillin

  • Antimicrobial options in patients who are allergic to penicillin include clindamycin or vancomycin [14]

  • Infections associated with diabetic ulcers are often polymicrobial; empiric coverage in this setting should include broad coverage of gram-positive, gram-negative, and anaerobic organisms [15]

  • If the cellulitis appears to be related to a furuncle or an abscess, or if it is a postsurgical situation, including coverage for MRSA is prudent for severe cases until culture and sensitivity information is available

Mammalian bites

CA-MRSA is not commonly associated with bite wounds. Cellulitis associated with mammalian bite wounds is often polymicrobial and should be treated empirically with antimicrobials that target anaerobic bacteria in addition to the common cellulitis pathogens, as described below:

  • Mild cases can be treated on an outpatient basis with amoxicillin-clavulanate; in patients with penicillin allergy, combination therapy is usually required; fluoroquinolone plus clindamycin or trimethoprim-sulfamethoxazole (TMP-SMX) plus metronidazole would be reasonable alternatives

  • Inpatients can be treated with ampicillin-sulbactam or piperacillin-tazobactam; alternative agents in patients with penicillin allergy would be the same as the above but in parenteral form

Odontogenic cellulitis

Cellulitis of odontogenic origin is typically polymicrobial. Identified organisms include viridans streptococci, Neisseria and Eikenella species, and the anaerobes Prevotella and Peptostreptococcus. Treatment includes the following:

  • IV regimens that have demonstrated therapeutic response include clindamycin or ampicillin-sulbactam

  • Oral regimens that have demonstrated therapeutic response include clindamycin or amoxicillin-clavulanate

Aquatic lacerations and punctures

Lacerations and puncture wounds sustained in an aquatic environment may be contaminated with bacteria such as Aeromonas hydrophila, Pseudomonas and Plesiomonas species, Vibrio species, Erysipelothrix rhusiopathiae, and others. Treatment in such cases includes the following:

  • Antibiotic treatment should address common gram-positive and gram-negative aquatic organisms

  • Appropriate antibiotic regimens for saltwater or brackish water include doxycycline and ceftazidime, or a fluoroquinolone

  • Appropriate regimens for injuries sustained in freshwater include a third- or fourth-generation cephalosporin (eg, ceftazidime or cefepime) or a fluoroquinolone (eg, ciprofloxacin or levofloxacin)

  • Apparent infection that is not responsive to initial courses of antibiotics as above should raise suspicion for Mycobacterium marinum infection; in such situations, wound biopsy for mycobacterial stains and culture should be considered

MRSA

In many communities, CA-MRSA is the most common isolate obtained from abscesses. [71] Antibiotics used to treat cellulitis associated with abscess or purulent drainage should target CA-MRSA until proven otherwise with culture data. In contrast, for outpatients with nonpurulent cellulitis, the IDSA recommends empiric therapy for infection due to beta-hemolytic streptococci, as it is believed that CA-MRSA plays an uncommon role in these scenarios. [67]

Mild cases that require only outpatient therapy may be treated with TMP-SMX or a tetracycline agent such as doxycycline or minocycline. Available data suggest that doxycycline and TMP-SMX are equivalent for the treatment of mild skin and soft-tissue infections (SSTIs). [72] It is important to note that TMP-SMX or tetracyclines may not have adequate streptococcal coverage and should not be the first choice unless purulence is present. [73] Clindamycin may also be a reasonable choice, depending on local sensitivities of CA-MRSA, but the IDSA estimates that up to 50% of MRSA isolates have intrinsic or constitutive resistance to clindamycin in some regions. [2]

In more severe cases that require parenteral antibiotics to cover MRSA, vancomycin, daptomycin, tigecycline, ceftaroline, and linezolid are appropriate choices. Data are more limited for the newer agents, but they have been shown to have similar efficacy to vancomycin in some clinical trials. [74] Daptomycin has been associated with more rapid resolution of signs and symptoms of cellulitis in some trials. [75, 76] However, vancomycin continues to be the drug of choice because of its overall excellent tolerability profile, efficacy, and cost. [74]

If tinea pedis is considered a possible cause of recurrent cellulitis episodes, treatment with a topical antifungal is recommended. Oral antifungals, such as itraconazole or terbinafine, may be considered in cases of refractory chronic changes or if onychomycosis is providing a source for repeated infection.

Table 1, below, provides an overview of empiric antibiotic therapy by etiology and anatomic location.

Table 1. Empiric Antibiotic Therapy for Cellulitis by Etiology and Anatomic Location (Open Table in a new window)

Location

Likely Organisms

Other Organisms

Complication/ Discussion

Antibiotic Regimen -- Oral/ Outpatient

Indication for Hospitalization

Antibiotic Regimen -- Parenteral/ Hospitalized

Uncomplicated cellulitis

Group A streptococci much more likely than Staphylococcus aureus

 

 

Cephalexin or dicloxacillin

or clindamycin

 

Cefazolin or oxacillin

or nafcillin

Cellulitis, concern for methicillin-resistant S aureus is a concern

Group A streptococci and S aureus

 

 

[(Cephalexin or dicloxacillin or clindamycin) plus trimethoprim/ sulfamethoxazole]

or

Clindamycin

 

Vancomycin

Daptomycin

Ceftaroline

Dog bite

Pasteurella species (50% of wounds)

S aureus

Streptococcus pyogenes

Staphylococci, streptococci

Aerobes --Moraxella and Neisseria

Anaerobes --Fusobacterium, Bacteroides, Porphyromonas, and Prevotella

Capnocytophaga canimorsus may cause sepsis in patients with asplenia/hepatic disease.

Avoid first-generation cephalosporins/ erythromycin/ dicloxacillin.

High likelihood of infection –

Prophylactic antibiotics indicated for the following wounds: deep puncture, hands, requiring surgical repair, immunocompromised host, venous or lymphatic compromise, crush injury.

Requires close follow-up care within 24-48 h.

Amoxicillin/ clavulanate

Penicillin allergic:

Moxifloxacin

Deep wounds or severe wounds;

infections not responding to oral antibiotics

Third-generation cephalosporin (ceftriaxone [Rocephin]) plus metronidazole

or

beta-lactam/beta-lactamase inhibitor (eg, ampicillin/sulbactam) or

fluoroquinolone plus metronidazole

or

carbapenem (ertapenem)

Human bite

Eikenella corrodens (gram-negative facultative anaerobe, 29% of wounds)

Aerobic gram-positive cocci, anaerobes

 

Clenched fist lacerations over metacarpophalangeal joints should be considered human bites; anesthetize wounds and irrigate; reevaluate within 24-48 h.

Intercanine distance >3 cm is likely bite from adult; if wound to child, consider abuse.

Amoxicillin/ clavulanate

Penicillin allergic:

Moxifloxacin

or

(Clindamycin or metronidazole) plus (doxycycline or cefuroxime or trimethoprim/ sulfamethoxazole)

 

Third-generation cephalosporin (Rocephin) plus metronidazole

or

beta-lactam/beta-lactamase inhibitor (eg, ampicillin/sulbactam)

or

fluoroquinolone plus metronidazole

or

carbapenem (ertapenem)

Cat bite

Pasteurella multocida and P septica (75% of wounds)

Staphylococci, streptococci, Bacteroides, Peptostreptococcus, Actinomyces, Fusobacterium, Porphyromonas, and Veillonella parvula

Avoid first-generation cephalosporins/ erythromycin/ dicloxacillin

High likelihood of infection -- Prophylactic antibiotics indicated for the following wounds: deep puncture, hands, requiring surgical repair, immunocompromised host, venous or lymphatic compromise.

Requires close follow-up care within 24-48 h.

Amoxicillin/ clavulanate

Penicillin allergic --

Moxifloxacin

or

(Clindamycin or metronidazole) plus

(doxycycline or cefuroxime or trimethoprim/ sulfamethoxazole)

Deep wounds or severe wounds; infections not responding to oral antibiotics

Third-generation cephalosporin (Rocephin) plus metronidazole

or

beta-lactam/beta-lactamase inhibitor (eg, ampicillin/sulbactam) or

fluoroquinolone plus metronidazole

or

carbapenem (ertapenem)

Preseptal (periorbital) cellulitis

Haemophilus influenzae type b, Streptococcus pneumoniae, S aureus, other streptococcal species, and anaerobes

Nocardia brasiliensis, Bacillus anthracis, Pseudomonas aeruginosa, Neisseria gonorrhoeae, Proteus species, Pasteurella multocida, Mycobacterium tuberculosis

Largest study indicates that H influenzae type b and S pneumoniae not diminished in facial cellulitis as a result of immunizations [25]

Amoxicillin-clavulanate, cefpodoxime, cefdinir

Age < 1 y/ more severe disease require intravenous antibiotic

Third-generation cephalosporin (Rocephin)

Lower extremity --

Complicating saphenous venectomy site after coronary bypass grafting

No pathogen identifiable in most infections, but it is likely to be streptococcal (> staphylococcal)

Non-group A beta-hemolytic streptococci most likely organism; S aureus less common

 

Recurrent episodes common; may be associated with rigors, extreme fatigue, myalgias, and hypotension; some associated with tinea pedis (toe web cultures may be useful in establishing probable pathogen)

Dicloxacillin or cephalexin.

Add trimethoprim/ sulfamethoxazole or tetracycline or clindamycin if concern for methicillin-resistant S aureus

 

First-generation cephalosporin (cefazolin); clindamycin; vancomycin

Breast/arm - - (not mastitis)

Complicating breast cancer surgery/lymph node dissection

No pathogen identifiable in most infections

Group A or Non-group A beta-hemolytic streptococci most likely organisms

 

 

Dicloxacillin, cephalexin. Add trimethoprim/ sulfamethoxazole or tetracycline or clindamycin if concern for methicillin-resistant S aureus

Fever, recent chemotherapy, neutropenia

Multiple regimens, none clearly superior –Piperacillin/tazobactam or ceftazidime plus aminoglycoside;

or

ciprofloxacin plus beta-lactam

or

monotherapy with piperacillin/tazobactam or cefepime

Aquatic environment --

Fresh water/ salt water/ brackish water/ swimming pools/ aquarium

Puncture/ laceration

Aeromonas hydrophila, Pseudomonas and Plesiomonas species, Vibrio species, Erysipelothrix rhusiopathiae, Mycobacterium marinum, and others

 

A hydrophila and Vibrio vulnificus may produce rapidly progressive soft-tissue infection and sepsis

Fluoroquinolone (eg, ciprofloxacin or levofloxacin)

Note: For M marinum infection, use clarithromycin plus either ethambutol or rifampin

 

Third- or fourth-generation cephalosporin (eg, ceftazidime or cefepime) or fluoroquinolone (eg, ciprofloxacin or levofloxacin)

Clenched-fist injury

E corrodens (gram-negative anaerobe, 29 % of wounds); aerobic gram-positive cocci, anaerobes

 

Lacerations over metacarpophalangeal joints should be considered human bites; anesthetize wounds and irrigate; reevaluate within 24-48 h

Lacerations of extensor tendon

Amoxicillin/ clavulanate; penicillin allergic:

Moxifloxacin

or

(clindamycin or metronidazole) plus (doxycycline or cefuroxime or trimethoprim/ sulfamethoxazole)

Failure to respond to oral therapy marked by increasing pain and swelling or purulent drainage

Beta-lactam/beta-lactamase inhibitor (eg, ampicillin/sulbactam)

Odontogenic facial cellulitis

Aerobic and facultative organisms: group A beta-hemolytic streptococci, Neisseria and Eikenella species

Anaerobes: Prevotella and Peptostreptococcus species

 

Require extraction or root canal

Amoxicillin-clavulanate

or

clindamycin

 

Beta-lactam/beta-lactamase inhibitor (eg, ampicillin/sulbactam) or

clindamycin

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Outpatient Care

Patients with cellulitis who have mild local symptoms and no evidence of systemic disease can be treated on an outpatient basis. Facial cellulitis of odontogenic origin requires extraction or root canal as well as antibiotic therapy. Elevating limbs with cellulitis expedites resolution of the swelling. Cool sterile saline dressings may be used to remove purulent discharge from any open lesion.

Treatment duration for cellulitis is controversial; shorter-duration therapy may be as effective as longer-duration therapy. [77] In general, consider the following:

  • A transient increase in erythema over the first day of treatment is common and represents an inflammatory reaction to cell lysis caused by antibiotics

  • The patient should be reassessed with short-interval follow-up—ideally within 48-72 hours—to ensure improvement.

  • In patients who respond slowly to therapy, antibiotics may need to be continued until inflammation resolves. If infection does not regress after outpatient treatment, antibiotic resistance or a more serious infection should be ruled out; an alternative diagnosis should also be considered

  • Development of systemic symptoms should prompt reevaluation and consideration for admission.

  • Concomitant hypotension and tachycardia indicate systemic disease and warrant intensive monitoring

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IV Antibiotic Therapy

Severely ill patients and those whose condition is unresponsive to standard oral antibiotic therapy should be treated with inpatient intravenous (IV) antibiotics. The selection of antibiotic therapy should be based on suspicion for likely organisms as well as results of Gram stain, culture, and drug susceptibility analysis, if available. [2]

In hospitalized patients in which S aureus infection is a concern, it is wise to assume methicillin (oxacillin) resistance because of the high prevalence of community-acquired methicillin-resistant strains (CA-MRSA); administer agents that are usually effective against MRSA, such as vancomycin, linezolid, ceftaroline, or daptomycin. [2] Step-down treatment for S aureus– related soft-tissue infections may focus upon tetracyclines, trimethoprim-sulfamethoxazole, or other agents, depending on the results of susceptibility tests and following an initial clinical response.

Other individuals who may require inpatient IV antibiotic include the following [8] :

  • Immunosuppressed patients

  • Patients with facial cellulitis

  • Any patient with a clinically significant concurrent condition, including lymphedema and cardiac, hepatic, or renal failure

  • Individuals with newly elevated creatinine, creatine phosphokinase, and/or low serum bicarbonate levels or marked left-shift polymorphonuclear neutrophils

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Surgical Examination and Drainage

Urgent consultation with a surgeon should be sought in the setting of crepitus, circumferential cellulitis, necrotic-appearing skin (bronzing), evolving bullae, rapidly evolving cellulitis, pain disproportional to physical examination findings, severe pain on passive movement, or other clinical concern for necrotizing fasciitis. Wong et al have developed a scoring tool to assist in the diagnosis of necrotizing fasciitis. [78] Cellulitis associated with an abscess requires surgical drainage of the source of infection for adequate treatment.

Serious concern for necrotizing fasciitis and/or the presence of necrotic skin should prompt examination of the fascial planes by immediate computed tomographic imaging or surgical direct observation, which, in most cases, can be performed at the bedside by an experienced surgeon. Circumferential cellulitis may result in compartment syndrome, which may require surgical decompression. Measurement of compartment pressures may be helpful in diagnosis.

See also the Medscape Reference article Skin and Soft Tissue Infections - Incision, Drainage, and Debridement.

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Impetigo

Although both Staphylococcus aureus and Streptococcus pyogenes cause impetigo ,historically, streptococcal infections were the most common, but recent series have indicated S aureus is now the leading cause. Management is based on the number of lesions, the location of the infection (eg, face, eyelid, mouth), and limiting infectivity. [2] The IDSA indicates mupirocin to be the best topical agent, despite some reports of resistance, and older preparations (eg, bacitracin and neomycin) to be much less effective. [2]

Administer oral antibiotic agents effective against both S aureus and S pyogenes in patients with many lesions or in those who do not respond to topical agents. [2] Note that some strains of S pyogenes may cause glomerulonephritis, a rare complication of impetigo, but there is currently no available evidence that treating impetigo will prevent glomerulonephritis. Also note that some strains of S aureus and S pyogenes may be resistant to erythromycin and erythromycin ethylsuccinate. [2]

The IDSA recommends use of the following antibiotics for managing impetigo in adults, with treatment duration of about 7 days (based on the clinical response) [2] :

  • Mupirocin ointment applied topically tid in patients with a limited number of lesions

  • Dicloxacillin, cephalexin, or  erythromycin 250 mg PO qid, or

  • Erythromycin ethylsuccinate 400 mg PO qid, or

  • Clindamycin 300-400 mg PO tid, or

  • Amoxicillin-clavulanate (875/125 mg) PO bid

In children (excluding neonates), the IDSA recommends the following antibiotic regimens, with treatment duration of about 7 days (based on the clinical response) [2] :

  • Mupirocin ointment applied topically tid in patients with a limited number of lesions

  • Dicloxacillin 12 mg/kg/day PO, in 4 divided doses

  • Cephalexin 25 mg/kg/day PO, in 4 divided doses

  • Erythromycin 40 mg/kg/day PO, in 4 divided doses

  • Clindamycin 10-20 mg/kg/day PO in 3 divided doses

  • Amoxicillin-clavulanate 25 mg/kg/day of the amoxicillin component PO in 2 divided doses

See also the Medscape Reference articles Cellulitis Organism-Specific Therapy, Cellulitis Empiric Therapy, Periorbital Cellulitis Organism-Specific Therapy, Periorbital Cellulitis Empiric Therapy, Orbital Cellulitis Organism-Specific Therapy, and Orbital Cellulitis Empiric Therapy.

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MSSA and MSRA SSTIs

MSSA SSTIs

The IDSA indicates the following adult antibiotic regimens may be used to treat methicillin-sensitive Staphylococcus aureus (MSSA) skin and soft-tissue infections (SSTIs) [2] :

  • Nafcillin or oxacillin 1-2 g IV q4h (IV agent of choice; inactive against methicillin-resistant S aureus [MRSA])

  • Cefazolin 1 g IV q 8h (for penicillin-allergic patients but not those with immediate hypersensitivity reactions)

  • Clindamycin 600 mg/kg IV q8h or 300-450 mg PO tid (may have cross-resistance and emergence resistance in erythromycin-resistant strains; induces resistance in MRSA)

  • Dicloxacillin (PO agent of choice for MSSA) or cephalexin (for penicillin-allergic patients but not those with immediate hypersensitivity reactions) 500 mg PO qid

  • Doxycycline or minocycline 100 mg PO bid

  • Trimethoprim-sulfamethoxazole (TMP-SMZ) 1-2 double-strength (DS) tablets PO bid

The IDSA indicates that the following pediatric (except neonates) antibiotic regimens may be used to treat MSSA SSTI [2] :

  • Nafcillin or oxacillin 100-150 mg/kg/day IV, in 4 divided doses (IV agent of choice; inactive against MRSA)

  • Cefazolin 50 mg/kg/day IV, in 3 divided doses (for penicillin-allergic patients but not those with immediate hypersensitivity reactions)

  • Clindamycin 25-40 mg/kg/day IV, in 3 divided doses, or 10-20 mg/kg/day PO, in 3 divided doses (may have cross-resistance and emergence resistance in erythromycin-resistant strains; induces resistance in MRSA)

  • Dicloxacillin (PO agent of choice for MSSA) or cephalexin (for penicillin-allergic patients but not those with immediate hypersensitivity reactions), 25 mg/kg/day PO in 4 divided doses

  • TMP-SMZ 8-12 mg/kg (based on the TMP component) in 4 divided doses IV or 2 divided doses PO

Doxycycline and minocycline are not recommended in children younger than 8 years.

MRSA SSTIs

The IDSA indicates that the following adult antibiotic regimens may be used to treat MRSA SSTIs [2] :

  • Vancomycin 30 mg/kg/day IV, in 2 divided doses (IV agent of choice for MRSA; penicillin-allergic patients)

  • Linezolid 600 mg IV q12h or 600 mg PO bid

  • Clindamycin 600 mg/kg IV q8h or 300-450 mg PO tid (may have cross-resistance and emergence resistance in erythromycin-resistant strains; induces resistance in MRSA)

  • Daptomycin 4 mg/kg IV q24h (may cause myopathy)

  • Doxycycline, minocycline 100 mg PO bid

  • TMP-SMZ 1-2 double-strength (DS) tablets PO bid

The IDSA indicates that the following pediatric (except neonates) antibiotic regimens may be used to treat MRSA SSTIs [2] :

  • Vancomycin 40 mg/kg/day IV, in 4 divided doses (IV agent of choice for MRSA; penicillin-allergic patients)

  • Linezolid 10 mg/kg IV q12h or PO

  • Clindamycin 25-40 mg/kg/day IV, in 3 divided doses, or 10-20 mg/kg/day PO, in 3 divided doses (may have cross-resistance and emergence resistance in erythromycin-resistant strains; induces resistance in MRSA)

  • TMP-SMZ 8-12 mg/kg (based on the TMP component) in 4 divided doses IV or 2 divided doses PO

In 2011, the IDSA published updated guidelines regarding management of MRSA in adults and children, and in 2012, the updated IDSA guidelines for the Diagnosis and Treatment of Diabetic Foot Infections were published. [67, 68] Readers are encouraged to check the IDSA guidelines Web site for the 2014 updated recommendations for the diagnosis and management of skin and soft-tissue infections. [2]

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Erysipelas and Cellulitis

As noted, streptococcal species are the most common causes of erysipelas and diffuse cellulitis or cellulitis that is not associated with a defined portal, and Staphylococcus aureus is the usual causative organism in cellulitis that is associated with furuncles, carbuncles, or abscesses. [2]

First-line treatment of erysipelas is either IV or PO penicillin, depending on the severity of the condition. In cases of cellulitis (except in areas with streptococcal/staphylococcal resistance), select a penicillinase-resistant semisynthetic penicillin or a first-generation cephalosporin. Clindamycin or vancomycin is an alternative in patients who are allergic to penicillin. [2]

In refractory cases, causes may include the following:

  • Unusual organisms

  • Streptococcal or staphylococcal resistance to the selected antimicrobial therapy

  • More severe conditions (eg, necrotizing fasciitis, myonecrosis)

Patients who exhibit clinical deterioration or increasing toxicity require an aggressive evaluation and management strategy with antimicrobial therapy dependent on the results of Gram stain, culture, and drug-susceptibility analysis, if these are available. [2]

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Necrotizing Infections

Common causes of monomicrobial necrotizing fasciitis include Streptococcus pyogenes, Vibrio vulnificus, and Aeromonas hydrophila. [2] Polymicrobial necrotizing fasciitis is more common, especially in postoperative patients or in those with comorbid conditions, such as peripheral vascular disease, diabetes, and decubitus ulcers.

Clostridium species such as C perfringens, C septicum, C histolyticum, and C novyi are toxic causes of life-threatening gas gangrene, usually as a result of significant penetrating trauma or crush injuries that interrupt the blood supply. [2] Other predisposing factors include intracutaneous injection of black tar heroin (C perfringens, C novyi) or spontaneous gas gangrene (C septicum) in individuals with colonic lesions, adenocarcinoma, or neutropenia. [2]

Emergent surgical evaluation and management is the first-line treatment in necrotizing fasciitis and gas gangrene in the presence of the following [2] :

  • Violaceous bullae

  • Skin sloughing

  • Rapid progression

  • Gas in the tissue (crepitus or seen radiographically)

The IDSA recommends IV clindamycin and penicillin therapy for severe group A streptococcal and clostridial necrotizing infections. [2] For mixed necrotizing infections, in which gas in deep tissues is a frequent finding, select antimicrobials with efficacy against aerobic gram-positive/gram-negative organisms and anaerobes.

The IDSA recommends the following as first-line antibiotic treatments in managing adult mixed necrotizing infections [2] :

  • Ampicillin-sulbactam 1.5-3.0 g IV q6-8h (for patients with severe penicillin hypersensitivity: clindamycin or metronidazole plus an aminoglycoside or fluoroquinolone; add an appropriate agent in the presence of [or if there is a suspicion of] staphylococcal infection) or  piperacillin-tazobactam 3.37 g IV q6-8h plus  clindamycin 600-900 mg/kg IV q8h plus ciprofloxacin 400 mg IV q12h

  • Imipenem-cilastatin 1 g IV q6-8h

  • Meropenem 1 g IV q8h

  • Ertapenem 1 g IV qd

  • Cefotaxime 2 g IV q6h plus  metronidazole 500 mg IV q6h or clindamycin 600-900 mg/kg IV q8h

The following are first-line treatments in managing adult S aureus (MSSA) infections [2] :

  • Nafcillin (for patients with severe penicillin hypersensitivity: vancomycin, linezolid, quinupristin-dalfopristin, or daptomycin; add an appropriate agent in the presence of [or if there is a suspicion of] staphylococcal infection) or oxacillin 1-2 IV q4h

  • Cefazolin 1 g IV q8h

  • Clindamycin 600-900 mg/kg IV q8h (may have cross-resistance and emergence resistance in erythromycin-resistant strains; induces resistance in MRSA)

First-line agents in managing severe adult streptococcal infection are penicillin 2-4 MU IV every 4-6 hours plus  clindamycin 600-900 mg/kg IV every 8 hours. [2] For patients with severe penicillin hypersensitivity, use vancomycin, linezolid, quinupristin-dalfopristin, or daptomycin. Add an appropriate agent if a staphylococcal infection is present or suspected.

For clostridial infections, first-line agents are clindamycin 600-900 mg/kg IV every 8 hours, as well as penicillin 2-4 MU IV every 4-6 hours.

Readers are encouraged to check the IDSA guidelines Website for the 2014 updated recommendations for the diagnosis and management of skin and soft-tissue infections.

See also the Medscape Reference articles Necrotizing fasciitis and Clostridial Gas Gangrene.

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Animal- or Human-Bite Infections

Animal bites

Pasteurella species are the most commonly found organisms in cat- and dog-bite wounds; however, on average, 5 different aerobic and anaerobic bacteria are isolated from such wounds (eg, S aureus, Bacteroides tectum, Fusobacterium, Capnocytophaga, or Porphyromonas). [2]

The severity and depth of the wound, as well as the time since the bite occurred, help clinicians determine antimicrobial management, such as route of administration (eg, IV, PO). In non–penicillin-allergic patients, administer amoxicillin-clavulanate PO or ampicillin-sulbactam IV or ertapenem IV. [2] Other agents are not recommended because of either poor activity against P multocida (eg, dicloxacillin, cephalexin, erythromycin, clindamycin) or inadequate anaerobic coverage (eg, cefuroxime, cefotaxime, ceftriaxone).

Patients with mild penicillin allergies may receive cefoxitin IV or carbapenem agents IV. Individuals with severe penicillin hypersensitivity may receive doxycycline, TMP-SMZ, or a fluoroquinolone plus clindamycin, either PO or IV. [2]

Human bites

As in animals, the human mouth is contaminated with multiple organisms; therefore, any human-bite wound necessitates early recognition and management to avoid complications and infection. Common culprits include aerobic organisms (eg, streptococci, S aureus, Eikenella corrodens), as well as anaerobic organisms (eg, Fusobacterium, Peptostreptococcus, Prevotella, Porphyromonas). [2]

The IDSA recommends parenteral ampicillin-sulbactam or cefoxitin therapy in patients with human-bite wounds, because E corrodens is resistant to first-generation cephalosporins, macrolides, clindamycin, and aminoglycosides. [2]

See also the Medscape Reference articles Animal Bites and Human Bites.

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Surgical Site Infections

In general, infections at surgical sites rarely occur in the first 48 hours after surgery, with the exceptions of group A streptococci or clostridial species. [2] The IDSA indicates that, usually, management with observation, dressing changes, or opening the incision is sufficient in patients with a temperature below 101.3°F (38.5° C) without tachycardia. [2]

Antibiotics and opening the incision are usually required in febrile patients with temperatures above 101.3°F (38.5° C) or tachycardia of 100 beats/min or greater. [2] Empiric therapy with agents active against the most likely organisms (eg, mixed gram-positive/gram-negative organisms for procedures involving the intestinal or genital tract; S aureus, MRSA, and streptococcal organisms for procedures involving nonintestinal sites) can be initiated until results from Gram stain and wound cultures are received. [2]

Procedures that involve nonsterile tissue (eg, intestinal/genital tract, respiratory mucosa) are frequently necessary because of mixed aerobic and anaerobic organism and can involve deeper soft tissues such as fascia and muscle. [2] The IDSA guidelines provide an algorithm, as well as a table of antibiotic selections, based on the operative site. [2]

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Infections in the Immunocompromised Host

Skin and soft-tissue infections (SSTIs) in immunocompromised patients can be caused by a variety of organisms, including those that don’t usually produce illness in healthy individuals, or may be the result of an underlying systemic infection. [2] The clinical findings of such SSTIs can be obscured by the degree and type of the patient’s immune deficiency.

Hospital-acquired SSTIs

Immunocompromised patients may acquire infections in the hospital, which can present a therapeutic challenge because of the emergence of resistant gram-positive and gram-negative bacteria. In general, severely ill or toxic patients require very broad-spectrum empiric agents that are effective against resistant gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA); these antimicrobials include vancomycin, linezolid, daptomycin, and quinupristin-dalfopristin. [2]

Ceftaroline is a new, advanced-generation cephalosporin that includes coverage for MRSA and that has received FDA approval for treatment of SSTIs. Gram-negative bacterial coverage includes monotherapy with a cephalosporin effective against strains of Pseudomonas (if such concerns exist with a patient), carbapenems, or a combination of either a fluoroquinolone or an aminoglycoside (monitor renal function), plus either an extended-spectrum penicillin or a cephalosporin. [2]

SSTIs in patients with cell-mediated immunodeficiency

Common or unusual bacteria (eg, Mycobacterium, Nocardia), viruses, protozoa, helminths, or fungi can cause SSTIs in patients with conditions such as Hodgkin disease, lymphoma, and human immunodeficiency virus (HIV) infection, as well as in patients who have had a bone marrow transplantation or have received long-term high-dose immunosuppressant therapy. [2] These patients require biopsy and early, aggressive management.

The IDSA guidelines provides a table of antibiotic selections based on the predisposing factor (eg, neutropenia, cellular immune deficiency) and pathogen (eg, bacteria, viruses, fungi). [2] Empiric treatment must be determined on the basis of local susceptibilities.

Readers are encouraged to check the IDSA Web site for the 2014 updated recommendations for the diagnosis and management of skin and soft-tissue infections.

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