Diabetic Foot Infections

etioologies of DFI

peripheral arterial disease (PAD) and peripheral neuropathy - arise from an ulcer or from wound caused by trauma

how are chronic ulcers formed?

foot deformitiy —→ repetitive trauma —→ chronic ulcer

poor vascular supply —→ delayed wound healing —→ chronic ulcer

hyperglycemia —→ oxidative stress —→ chronic ulcer

classic clinical presentation of DFI

redness, warmth, swelling, tenderness, pain, purulent drainage (>= 2 are necessary to call a wound infected)

secondary findings for DFI

non-purulent secretions, discolored granualtion tissue, foul odor

assessment of wound:

depth and tissues involved, requires debridement of necrotic tissue, looking for abscesses, sinus tracts, foreign bodies, probe to bone

T/F: x-rays are recommended for all DF wounds and if bone involvement is suspected, an MRI is the study of choice

true

classify mild DFI

local infection involving only the skin and the subq tissue, if erythema is present, must be 0.5-2 cm aaround the ulcer, exclude other causes of inflammatory response of skin

Classify moderate DFI

Local infections as described in mild scenarios with erythema > 2 cm or involving structures deeper than skin and subway tissues, no SIRS

Classify severe DFI

Local infection as described in moderate scenarios with signs of SIRS as manifested by >= 2 of the following: temp 38-36 Celsius, HR >90, RR >20, WBC >12,000 or <4,000

Define wound

Penetrates to subcutaneous tissues (fascia, tendon, muscle, joint and bone)

Define cellulitis

Extensive (>2 cm) distance from ulceration or rapidly progressive

Define local signs

Severe inflammation or induration, crepitus, Bullard, discoloration, necrosis or gangrene, chemises or petechiae, and new anesthesia

Presentation of systemic DFI

Acute onset/worsening or rapidly progressive

Systemic signs of DFI

Fever, chills, hypotension, confusion, and volume depletion

Lab tests for systemic DFI

Leukocyte is, very high CRO/ESR, severe/worsening hyperglycemia, acidosis, AKI, and electrolytes abnormalities

Complicating features of systemic DFI

Presence of a foreign body (accidentally or surgically implanted), puncture wound, deep abscess, arterial or venous insufficiency, lymphedema, immunosuppressive illness or treatment

Treatment for systemic DFI

Progression on appropriate antibiotic and supportive therapy

T/F: you should not culture a clinically uninfected wound

True

In moderate and severe infections multiple organisms are likely and multi-resistant organisms may be possible therefore _______ are essential

Cultures

How should samples/cultures be obtained for DFIs?

Deeper tissue cultures or aspirates of prudent secretions - superficial swabs are much less helpful

Typical bacteria involved in DFIs:

staph and strep most common, sometimes pseudomonas, and anaerobes play more of a role in moderate-severe infections (may not need to cover if wound has been adequately debriefed)

Risk factors for MRSA DFIs

History of MRSA colonization, severe infections, extensive surgical procedures

Risk factors for pseudomonas DFIs:

Warm climate and frequent exposure to water

Risk factors for MRSA and pseudomonas DFIs:

Extensive antimicrobial use in the past 30-60 days, hx infections for each respectively, and high local prevalence

Empirical therapy for mild DFI

cephalexin (MSSA), Amox/clav, clindamycin, Bactrim (MRSA), and doxycycline (MRSA)

Empiric therapy for moderate-severe DFI for MSSA

Amp/sulb, dedication, ceftriaxon + metronidazole, cipro + blinds, moxifloxacin, and ertapenem

Empiric therapy for MRSA mod-severe DFI

Vanco, linezolid, and dapto

Empiric therapy for mod-severe DFI from pseudomonas

P/T and Cefepime

Empiric therapy for MRSA + pseudo + anaerobe DFIs

Vanco + P/T

Vanco + cefepime + metronidazole

Vanco + meropenem

Route of antibiotics for mild DFI

Oral

Duration of therapy for mild DFI

1-2 weeks - may require longer if slow to respond

Route of antibiotic in moderate DFI

Oral or IV transition to oral

Duration of therapy for moderate DFI

1-3 weeks

Route of antibiotics for severe DFI

IV transitioned to oral

Duration of therapy for severe DFI

2-4 weeks