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Anaerobic Infections, Skin & Soft Tissue

For further information, see CMDT Part 33-31: Anaerobic Infections

Key Features

  • Several terms are used to classify these infections

    • Bacterial synergistic gangrene

    • Synergistic necrotizing cellulitis

    • Necrotizing fasciitis (see Necrotizing Fasciitis)

    • Nonclostridial crepitant cellulitis

  • Usually occur after trauma, ischemia, or surgery

  • Most common in areas contaminated by oral or fecal flora

  • May also be seen in individuals who inject drugs and persons sustaining animal bites

  • All are mixed infections caused by aerobic and anaerobic organisms

  • Although there are some differences in microbiology among these infections, differentiation on clinical grounds alone is difficult

Clinical Findings

  • There may be progressive tissue necrosis, evidence of gas in the tissues (crepitance) and a putrid odor

  • Pain out of proportion to the clinical findings

  • Hemodynamic instability and systemic toxicity may be present

Diagnosis

  • Surgical exploration

Treatment

  • Broad-spectrum antibiotics active against both anaerobes and gram-positive and gram-negative aerobes (eg, intravenous vancomycin plus piperacillin-tazobactam, 4.5 g intravenously every 8 hours) should be instituted empirically and modified by culture results (Tables 30–4 and 30–5)

  • They are given about a week after progressive tissue destruction has been controlled and the margins of the wound remain free of inflammation

  • Aggressive surgical debridement of necrotic tissue is required for cure

Table 30–4.Medication of choice for suspected or documented microbial pathogens (listed in alphabetical order, within classes).
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Table 30–4. Medication of choice for suspected or documented microbial pathogens (listed in alphabetical order, within classes).
Suspected or Proved Etiologic Agent Medication(s) of First Choice Alternative Medication(s)

Gram-Negative Cocci

Moraxella catarrhalis

Cefuroxime, amoxicillin-clavulanic acid

Ceftriaxone, cefuroxime axetil, a fluoroquinolone,1 a macrolide,2 a tetracycline,3 TMP-SMZ4

Neisseria gonorrhoeae (gonococcus)

Ceftriaxone + azithromycin or doxycycline

Cefixime + azithromycin or doxycycline5

Neisseria meningitidis (meningococcus)

Penicillin6

Ceftriaxone, ampicillin

Gram-Positive Cocci

Enterococcus faecalis

Ampicillin ± gentamicin7

Ampicillin ± ceftriaxone

Vancomycin ± gentamicin

Enterococcus faecium

Vancomycin ± gentamicin7

Linezolid,8 quinupristin-dalfopristin,8 daptomycin,8 tigecycline,8 tedizolid,8 oritavancin8

Staphylococcus, methicillin-susceptible

Cefazolin

or

Penicillinase-resistant penicillin10

Vancomycin, a cephalosporin,9 clindamycin, amoxicillin-clavulanic acid, ampicillin-sulbactam

Staphylococcus, methicillin-resistant

Vancomycin

TMP-SMZ,4 doxycycline, minocycline, linezolid,8 tedizolid,8 daptomycin,8 televancin,8 dalbavancin,8 oritavancin,8 ceftaroline, delafloxacin

Streptococcus, hemolytic, groups A, B, C, G

Penicillin6

Macrolide,2 a cephalosporin,9 vancomycin, clindamycin

Streptococcus pneumoniae11 (pneumococcus)

Penicillin6

A cephalosporin,9 vancomycin, clindamycin, a tetracycline,3 respiratory fluoroquinolones1

Viridans streptococci

Penicillin6

Cephalosporin,9 vancomycin

Gram-Negative Rods

Acinetobacter

Imipenem, meropenem

Tigecycline, minocycline, doxycycline, aminoglycosides,12 colistin, cefiderocol

Bacteroides, GI strains

Metronidazole

Ampicillin-sulbactam, piperacillin-tazobactam, ertapenem

Brucella

Doxycycline + rifampin3

TMP-SMZ4 ± gentamicin; ciprofloxacin + rifampin

Burkholderia mallei (glanders)

Streptomycin + tetracycline3

Chloramphenicol + streptomycin

Burkholderia pseudomallei (melioidosis)

Ceftazidime

Tetracycline,3 TMP-SMZ,4 amoxicillin-clavulanic acid, imipenem or ...

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