Transcript Wound Care Pelz

Infectious complications of
the diabetic foot
Bob Pelz, MD PhD
I have no relevant
disclosures
Epidemiology
• 15% of diabetics develop ulcers, 6%
require hospitalizaitons
• Over half of ulcers become infected
• 20-66% of infected ulcers involve
bone
Spectrum of infections
• Cellulitis
• Abscess
• Osteomyelitis
Differential diagnosis
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Non-infected neuropathic ulcer
Fracture
Ischemia
Embolization, vasculitis, stasis ulcer,
carcinoma
Evaluation overview
Pathogenesis
• Sensory neuropathy
– Trauma, deformity
• Autonomic neuropathy
– Diminished sweat, dry, cracked skin
• Hyperglycemia
– Decreased neutrophil function
• Arterial disease
Pathogenesis
Challenges in Diagnosis of
Osteomyelitis
• Neuropathic changes may resemble
infection on MRI, other images
• Superficial cultures correlate poorly
with deep organisms, and may not
reflect deep infection at all
• Radiographic signs absent early
• Bone biopsy invasive, expensive,
inaccurate
Diagnosis of Osteomyelitis
• Labs: ESR > 70
• Radiology
– MRI, Labeled wbc, plain film
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Probe to Bone
Bone biopsy for histopathology, Cx
Surface cultures
Wound > 2 cm2
Plain radiographs
• Cheap and often very helpful
• Moth-eaten necrotic bone is dead
and requires surgery
Probe-to-bone
• Grayson, JAMA 1995. 75 inpatients,
66% with osteomyelitis
– “On gentle probing, the evaluator detected
a rock-hard, often gritty structure without
the apparent presence of any intervening
soft tissue”
– Gold standard- histo or clinical + radiology
– Sens/spec/PPV/NPV: 66,85,89,56%
Probe to Bone
• Lavery et al (Diab. Care 2007): 247 outpts, 12% with OM.
– S / S / PPV / NPV=87 / 91 / 57 / 98.
• Shone, et al Diab Care 2006
– Sensitivity / Specificity 0.38 / 0.91
• Aragon-Sanchez, Diab Med 2011 PTB or X ray +. Gold
standard = Bx with path showing osteo
– Sens / Spec 0.97 / 0.92. LR +/- 12.8 / 0.02
– 85% of those with pos path had pos Cx
• With exposed bone or positive probe to bone,
IDSA guidelines (2004) say X- ray not needed
Bone Bx
• Gold standard in most studies
• Open Bx more accurate than needle
– 31 pts, both needle and open (Seneville, CID 2009)
– 23.9% correlation between open Bx and
needle Biopsy Cx
• Highest with Staph aureus (46.7%)
– 41.7 correlation between swab Cx and
biopsy culture
• 82.3 for Staph aureus
Bone Biopsy
• Weiner (J Foot Ankle Surg 2011) 44 pts with clinical
osteo.
– Just as likely for Bx to be pos by micro as by histo
• Pos Cx rate low- 34% of 41 histologic
osteomyelitis
– 4 pos Cx in 34 histo-neg pts (Wu et al AJR 2007)
• White, et al (Radiology 1995) Culture swab
sensitivity 42%. 50% of histo-positive Bx had
positive Cx
– Should send Bx specimens for both Cx and histo
Superficial cultures, pitfalls
• Poorly predictive of deep pathogens
– 44% of sinus tract Cx contained
organism from surg sample (Mackowiak JAMA 1978)
– 28% concordance, 38% for staph (Zuluaga
BMC Infect Dis 2002)
– Twice as many bacteria species isolated
by swab than by Bx (Kessler, Diab Med 2005)
Superficial Cx, advantages
• Can often choose ABX to cover all
plausible organisms
• Organisms isolated repeatedly and in
large numbers likely to be causative
• Useful for detecting MRSA, other
MDRO
• Staph aureus likely pathogen if found
Osteomyelitis diagnosis,
Meta-analysis
Test
LR positive
LR Negative
Ulcer > 2cm2
7.2
.48
Positive probe to bone
6.4
.39
ESR >70
11
Abnormal X ray
2.3
Positive MRI
3.8
Butalia, et al. JAMA 2008
0.14
Osteomyelitis diagnosis,
Meta-analysis
Dinh, MT, CID 2008
Osteomyelitis Treatment
• Aerobic GPCs are the predominant
pathogens in diabetic foot infections
• Broad-spectrum empirical therapy is
not routinely required but is
indicated for severe infections
• Acute infections are often
monomicrobial (almost always with
aerobic GPC)
Lipsky et al, CID, 2004
Microbiology
Lipsky, et al. CID 2004
Antibiotics
• Surgery vs abx vs both.
– ABX can’t sterilize dead bone
• IV vs po
– Easier to monitor therapy with IV,
especially through RIC or in SNF
– IV may be preferable if litigious or
unreliable pt
– IV expensive, PICC risks (DVT, infection,
etc.)
IV Antibiotics, MRSA
Antibiotic
Pro
Con
Vancomycin
Cheap, safe, active against
MRSA
Monitor level. Infusions slow,
often BID. Poor bone
penetration. Weak antibiotic
Daptomycin
Once daily, rapid infusion,
good bone penetration
$150ish a dose wholesale
Televancin
As for daptomycin
Ceftaroline
Good tissue penetration,
highly active
BID, cost. Spectrum may be
overly broad.
IV Antibiotics, MSSA
Antibiotic
Pro
Con
Nafcillin
Most active, narrow
spectrum
Q 4 hours or CAD pump
Ceftriaxone
Q day. Covers many
gram negatives
Least in vitro activity of
the 3
Cefazolin
Activity between
nafcillin and
ceftriaxone
Q 8 hours
Oral antibiotics
Antibiotic
Pro
Con
Rifampin
Good bone, biofilm
penetration. Given with
Vanco, FQs, others
Nausea, LFTs.
Resistance, drug
interactions
TMP/SMX
Cheap, good tissue
penetration
Allergy, renal issues
Doxycycline/Mino
Cheap, good bone
penetration
GI issues with doxy.
Static, not ‘cidal
Fluoroquinolones
Good data when used with
rifampin. Good bone
penetration
Cipro has poor gram
positive activity. C. diff
with levo. Tendinopathy
Linezolid
Bioavailability about 100%.
Up to $100 a tablet.
MAOI, low platelets
IV vs PO therapy
• IV Cloxacillin vs Bactrim/rif, 50 pts with
surgical Cx, RCT. (Euba AAC 2009)
– Relapses no different with 7-9 years f/u
• Gentry, et al (AAC 1991) Ofloxacin vs IV, Bxconfirmed osteo.
– 74% vs 86% w/out relapse at 18 month f/u
• Fleroxacin/rif vs IV: 89% vs. 69% cure
(Schrenzel, CID 2004)
• Ofloxacin/Rif: Diabetic foot Staph. osteo.
76% relapse free at 22 mo. (Senneville CID 2001)
IV vs PO therapy
• 9/11 osteo cured with Rif/Linezolid vs
9/10 with Rif/Bactrim (Nguyen Clin Micro Infect 2009).
Similar cure with infected hardware.
• Linezolid vs Unasyn or vanco
(MRSA). 45 sites, 8 countries. (Lipsky, CID
2004) Excluded ischemic feet. 371 pts.
Cured osteo in 27/44 Linezolid, 11/16
unasyn. More AEs in L arm, but mild
IV vs PO therapy
• Generally, cure rates with IV and po
therapy comparable. Rifampin almost
always given.
Duration of therapy
• 4-6 weeks typical, but not based on
randomized data
• IV followed by 3 months po if
inadequate debridement
Case
• 60, dm, h/o right 4th and
5th ray amputations,
retinopathy, neuropathy
• 4/27/11- Fever, Acute
red, tender foot.
– MRI cuboid edema, ?5th
met osteo. No abscess
– Cx- Group B Strep
– Keflex 1 week
– Offloading
Case
• 5/10/11 Foot red, 1
week off keflex
– X ray- no osteo
– CRP- 0.7
• 5/24 pus, CRP=9.7,
Cx=GBS, faxed in 20
days doxycycline
• 5/31 erythema better
• 7/11 Total contact cast
Case, cont.
• 8/1/11 Copious
drainage, necrotic
base, +/- PTB despite
total contact cast
– X ray- still no osteo.
– Tagged WBC c/w
osteo
– TcPO2 42
Case, cont
• To OR, 8/11/11
– Path- no osteo, but
possible fracture
– Cx- Proteus, enterococcus
– 2 weeks keflex
– Wound improving with
resection of weightbearing 5th metatarsal
– Wound healed as of 9/11
Case summary
• 8 ID, 3 ortho, 13 wound care encounters
over 5 months
– 3 X rays, 1 MRI, 1 bone/WBC scan, TCC, surg
• Cellulitis, possible abscess, but osteo
never definite clinically, probably never
had it despite positive cultures.
• Fracture vs infection
• Ulcer due to abnormal weight bearing,
resolved with surgery
• Lives with son who is nearly blind
Take-homes
• Diagnosis and management of infected
foot ulcers difficult, requires team
approach
• Anaerobes, resistant gram negatives
not as common as taught. Staph
aureus is at least half of infections.
• Swab Cx, probe to bone, X rays useful
• Oral therapy likely as good as IV