Skin and Soft tissue Infections

Cellulitis

General points

• Common pathogens are S. aureus including MRSA & pyogenic streptococci (Groups A, C & G streptococci).
• Consider other pathogens if trauma, water or other exposures - Contact microbiology for advice.
• Review previous microbiology test results for MRSA and susceptibility profiles of other potential pathogens particularly if allergic to penicillin.
• Swab culture is not recommended as principle for identifying the causative bacteria in cellulitis patients. However, in immunosuppressed patients or those with neutropenia or in severe forms associated with systemic signs of inflammation or that do not respond to first-line therapy, culture may be helpful to identify the causative bacteria and define a targeted therapy.

Antibiotics (Empiric therapy)

First Line:

Flucloxacillin 2g QDS IV.

Oral switch/mild cellulitis: Flucloxacillin 500mg-1g QDS PO.

Penicillin allergy:

NOT IgE mediated reaction/anaphylaxis:

Cefuroxime 750mg- 1.5g TDS IV.

Oral switch/mild cellulitis: Cefalexin 500mg-1g TDS PO

Severe IgE mediated reaction/anaphylaxis to penicillin:

Clindamycin 300-450mg QDS PO OR 600mg- 1.2g QDS IV if oral administration not possible.

If known or suspected MRSA add Vancomycin or Teicoplanin to the all of the above regimes whilst awaiting culture results. For oral switch for proven MRSA infection contact microbiology to discuss. (Please see Vancomycin / Teicoplanin dosing schedule).

Severe cellulitis: as above

AND add Vancomycin or Teicoplanin as some strains of S. aureus and streptococci can be resistant to clindamycin. (Please see Vancomycin / Teicoplanin dosing schedule).

Consider the addition of Clindamycin 450mg QDS PO for 3-5 days. IV route may be indicated. Discuss these patients with the microbiology. As clindamycin is associated with a risk of C. difficile infection, short treatment courses are usually advised.

Comments

Duration : 5 days, may extend to 7-10 days if lack of symptom resolution at 5 days.

• Incision and drainage may be required in purulent cellulitis.

• Consider potential for deep seated infection such as underlying osteomyelitis if cellulitis related to ulcer or wound.
• Severe cellulitis should not be treated with a macrolide (erythromycin/clarithromycin).
• In confirmed Group A streptococcal infection discuss with microbiology and change to Benzylpenicillin IV + Clindamycin.

Orbital & Peri-Orbital Cellulitis

General points

• Orbital cellulitis is an ophthalmic emergency.
• Urgent ophthalmology and/or ENT referral advised.
• Consider intra-cranial / CNS involvement.
• Out-rule odontogenic source.
• Send blood cultures and swab for culture if purulent discharge.

Antibiotics (Empiric therapy)

Peri-orbital cellulitis (non-severe)

Co-amoxiclav 625mg TDS PO or 1.2g TDS IV

Penicillin allergy : Doxycycline 200mg stat then 100mg once daily PO.

P eri-orbital cellulitis (severe or with systemic toxicity) & all Orbital Cellulitis

Flucloxacillin 1-2g QDS IV

+

Ceftriaxone 2g BD IV

+

Metronidazole 400mg TDS PO

If known or suspected MRSA change use Vancomycin OR Teicoplanin instead of Flucloxacillin above while awaiting culture results. (Please see Vancomycin / Teicoplanin dosing schedule).

Oral switch when clinically improved Co-amoxiclav 625mg TDS PO. If MRSA isolated contact microbiology for advice.

Severe IgE mediated reaction/anaphylaxis to penicillin:

*Levofloxacin 500mg BD PO

+

Metronidazole 400mg TDS PO

+

Vancomycin (Please see Vancomycin dosing schedule).

* Please read the HPRA Drug Safety Alert issued in 2018 and the HPRA Drug Safety Newsletter issued in 2023 highlighting restrictions on use of fluoroquinolones (eg. ciprofloxacin, levofloxacin) due to the risk of disabling, long-lasting and potentially irreversible side effects (including tendon damage, QT prolongation, neuropathies and neuro psychiatric disorder). Use of fluoroquinolones in older patients, those with renal impairment, solid organ transplantation or on systemic corticosteroids increases the risk of tendon damage.

Comments

• Review empiric therapy with microbiology test results after 48h.
• Discuss with Clinical Microbiologist regarding duration of antibiotics.

Necrotising Soft Tissue Infections

General points

• Includes necrotising cellulitis, myositis, and cellulitis.
• Characterised by fulminant tissue destruction, systemic toxicity and high mortality.
• Early recognition of necrotising infection is crucial as surgical management can be life-saving.

When to suspect:

Soft tissue infection + signs of systemic illness + any of the following:

• Crepitus; skin discolouration or necrosis; thin, foul smelling wound discharge
• Rapid progression of clinical manifestations
• Severe pain (often out of proportion to exam findings)

Potentially involved sites:

• Upper and lower limbs
• Surgical or traumatic wounds
• Fournier’s gangrene (perineum)
• Head and neck region (odontogenic infections)

Antibiotics (Empiric therapy)

Necrotising soft tissue infections are a surgical emergency.

Urgent surgical review is required in suspected cases.

First Line:

Piperacillin-tazobactam 4.5g QDS IV

+

Clindamycin 1.2g QDS IV

+

Gentamicin once daily IV (Please see Gentamicin dosing schedule).

If known or suspected MRSA add Vancomycin (Please see Vancomycin dosing schedule).

Penicillin allergy:

NOT IgE mediated reaction/anaphylaxis:

Meropenem 1g TDS IV

+

Clindamycin 1.2g QDS IV

+

Gentamicin once daily IV (Please see Gentamicin dosing schedule).

If known or suspected MRSA add Vancomycin (Please see Vancomycin dosing schedule).

Severe IgE mediated reaction/anaphylaxis to penicillin:

Vancomycin (Please see Vancomycin dosing schedule).

+

Clindamycin 1.2g QDS IV

+

*Ciprofloxacin 400mg BD-TDS IV

+

Amikacin once daily IV. (Please see Amikacin dosing schedule)

Antimicrobial therapy can be de-escalated and rationalised post-surgical debridement, once pathogen(s) identified and clinical condition has stabilised.

• *Please read the HPRA Drug Safety Alert issued in 2018 and the HPRA Drug Safety Newsletter issued in 2023 highlighting restrictions on use of fluoroquinolones (eg. ciprofloxacin, levofloxacin) due to the risk of disabling, long-lasting and potentially irreversible side effects (including tendon damage, QT prolongation, neuropathies and neuro psychiatric disorder). Use of fluoroquinolones in older patients, those with renal impairment, solid organ transplantation or on systemic corticosteroids increases the risk of tendon damage.

Comments

• The management of necrotising fasciitis is primarily surgical with debridement of non-viable tissue to halt the spread of infection.
• Antibiotics should be reviewed after surgery and in conjunction with culture results.
• If Group A Streptococcal infection confirmed, consider change to IV Benzylpenicillin plus Clindamycin, following discussion with Microbiologist. Consider IV immunoglobulin (IVIG).
• Modify treatment according to Microbiology results and clinical response.

Human and Animal Bites

General points

• Cleaning, irrigation, and debridement are most important.
• Check tetanus status and consider tetanus prophylaxis.
• Consider risk for blood-borne viruses, HBV, HCV, and HIV with human bites.
• Consider rabies risk if animal bite https://www.hpsc.ie/a-z/zoonotic/rabies/guidance/File,12993,en.pdf

Antibiotics (Empiric therapy)

First Line:

Co-amoxiclav 625mg TDS PO or 1.2g TDS IV depending on severity.

Penicillin allergy:

Doxycycline 100mg BD PO + Metronidaziole 400mg TDS PO.

Severe infection:

Non-IgE mediated allergy: Ceftriaxone 2g once daily IV + Metronidazole 500mg TDS IV

IgE mediated penicillin allergy:* Ciprofloxacin 400mg BD IV + Metronidazole 500mg TDS IV

Discuss severe infection with microbiology as additional agents may be required.

Ciprofloxacin and Metronidazole have excellent oral bioavailability. Early change to oral administration is recommended.

• Please read the HPRA Drug Safety Alert issued in 2018 and the HPRA Drug Safety Newsletter issued in 2023 highlighting restrictions on use of fluoroquinolones (eg. ciprofloxacin, levofloxacin) due to the risk of disabling, long-lasting and potentially irreversible side effects (including tendon damage, QT prolongation, neuropathies and neuro psychiatric disorder). Use of fluoroquinolones in older patients, those with renal impairment, solid organ transplantation or on systemic corticosteroids increases the risk of tendon damage.

Comments

• Tailor antimicrobial therapy to culture results.
• Duration for prophylaxis: 3-5 days with follow up.
• Duration for treatment: 5 days, may extend therapy to 7-10 days if lack symptom resolution at 5 days depending on severity and clinical response.
• Note: Flucloxacillin, cefalexin, and macrolides (clarithromycin) do not have activity against Pasteurella spp and are therefore not recommended for the prophylaxis or treatment of infection due to animal bites.

References

WSES/GAIS/WSIS/SIS-E/AAST global clinical pathways for patients with skin and soft tissue infections. World journal of emergency surgery 2022.