Antibiotic use for SKIN infections

You don't need vancomycin for most NONPURULENT cellulitis, since Streptococcus is the most common pathogen. Use a beta-lactam, such as cefazolin......

As a clinical pharmacist, you will get questions about empiric antibiotic choices for patients hospitalized with skin infections. These patients may have more severe infections or have failed oral therapy. Broad-spectrum empiric antibiotics are often started, but they aren't always needed. Work with your antimicrobial stewardship team to limit antibiotic options based on indication, patient risks, and illness severity, "see table 1".

Is vancomycin needed for gram-positive coverage?

Not always. You don't need vancomycin for most NONPURULENT cellulitis, since Streptococcus is the most common pathogen.
Use a beta-lactam, such as cefazolin, instead. But continue to consider empiric vancomycin to cover methicillin-resistant Staph aureus (MRSA) in PURULENT skin infections or those resulting from a penetrating trauma, such as from injecting illicit drugs.

When should gram-negative or anaerobic coverage be added?

Only for certain infections.

For example, consider polymicrobial coverage with ampicillin/sulbactam (Unasyn, Unictam, etc) for diabetic foot infections or infected wounds from animal bites.

But don't empirically cover for Pseudomonas unless there are additional risk factors, such as a diabetic foot infection in a patient with frequent hot tub exposure.

Table (1). Drug Treatments for Skin and Soft Tissue Infections
Type of Infection	Factors to Consider	EMPIRIC Treatment Options	Comments
Nonpurulent Infection Cellulitis Erysipelas Necrotizing infection	Mild infection	PO PCN or amoxicillin PO cephalosporin (e.g., cephalexin) PO clindamycin	Target bacteria for empiric therapy: Streptococcus
	Moderate infection (i.e., with systemic signs of infection)	IV penicillin Ceftriaxone Cefazolin IV clindamycin	Target bacteria for empiric therapy: Streptococcus, MSSA Include MRSA coverage for patients with penetrating trauma, evidence of MRSA infection at another site, nasal colonization with MRSA, or injection drug use
	Severe infection (i.e., oral antibiotic failure, SIRS, immunocompromise, signs of deeper infection, or evidence of organ dysfunction) Note: Some experts suggest a narrower definition of severe infection, such as SIRS plus hypotension, rapid progression, or immunocompromise.	IV vancomycin, plus piperacillin/tazobactam, imipenem, meropenem, or cefepime	Broad-spectrum empiric coverage is recommended When culture results are available, options include: S. pyogenes or Clostridium species: Penicillin plus clindamycin Vibrio vulnificus: Doxycycline plus ceftazidime, ceftriaxone, or cefotaxime Aeromonas hydrophila: Doxycycline plus ciprofloxacin or ceftriaxone Polymicrobial infection: Vancomycin plus piperacillin/tazobactam or a carbapenem, or cefotaxime plus metronidazole or clindamycin
Purulent Infection Abscess* Carbuncle* Furuncle * Gram stain/culture recommended, but treatment without these studies is reasonable in typical cases.	Mild infection	No antibiotic treatment necessary	Incision and drainage alone is recommended in the absence of systemic signs of infection
	Moderate infection (i.e., with systemic signs of infection or multiple abscesses)	TMP/SMX Doxycycline Minocycline Clindamycin	Target bacteria for empiric therapy: MRSA When culture results are available: MRSA: TMP/SMX MSSA: Dicloxacillin or cephalexin
	Severe infection (i.e., treatment failure with incision and drainage/oral antibiotics, SIRS, immunocompromise)	Vancomycin Daptomycin Linezolid (Zyvox) Ceftaroline (Teflaro)	Target bacteria for empiric therapy: MRSA When culture results are available: MRSA: Any of the empiric treatments MSSA: cefazolin, or clindamycin
Surgical Wound Infection	≤4 days after surgery with systemic illness and signs of wound infection	Penicillin plus clindamycin	Target bacteria for empiric therapy: Streptococcus Clostridium species
Surgical Wound Infection	> 4 days after surgery with SIRS, plus signs of wound infection	Surgery on trunk, head, neck, or extremities: Cefazolin Vancomycin (if patient has serious B-lactam allergy) Surgery on perineum, axilla, GI tract, or female genital tract: Cephalosporin plus metronidazole Levofloxacin plus metronidazole Carbapenem	Target bacteria for empiric therapy: MSSA MRSA, if there are risk factors such as nasal colonization, prior MRSA infection, recent hospitalization, or recent antibiotics Gram-negative bacteria and anaerobes, if surgery involved axilla, GI tract, perineum, or female genital tract
Abbreviations: MRSA = methicillin-resistant S. aureus, MSSA = methicillin-sensitive S. aureus, PCN = penicillin, SIRS = systemic inflammatory response syndrome, TMP-SMX = trimethoprim-sulfamethoxazole, WBC = white blood count.

When should resistant pathogens be considered?

Primarily in high-risk patients or severe infections.

For example, in immunosuppressed patients, consider Pseudomonas coverage with cefepime (Maxipime, Pimfast) piperacillin/tazobactam (Tazocin, Pipra-Taz) plus vancomycin for MRSA.

Think about similar broad-spectrum coverage for necrotizing fasciitis patients. And add clindamycin (Dalacin) to suppress toxin production.
Be aware that redness around the infection may expand before it gets better. Consider waiting 48 hours before adjusting antibiotics if this is your primary indicator of treatment failure.

Image Source: Clin Infect Dis. 2014 Jul 15;59(2):e10-52.

Management of soft tissue infections (SSTIs).

References

Raff AB, Kroshinsky D. Cellulitis: A Review. JAMA. 2016 Jul 19;316(3):325-37.
Stevens DL, Bisno AL, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the infectious diseases society of America. Clin Infect Dis. 2014 Jul 15;59(2):147-59.
Walsh TL, Chan L, Konopka CI, Burkitt MJ, Moffa MA, Bremmer DN, Murillo MA, Watson C, Chan-Tompkins NH. Appropriateness of antibiotic management of uncomplicated skin and soft tissue infections in hospitalized adult patients. BMC Infect Dis. 2016 Nov 29;16(1):721.