Transcript Diabetic foot infection

Diabetic foot infection
Dr Paul Chadwick
Consultant Microbiologist
Salford Royal Hospital
Case History
• A 76 year old man was admitted as an
emergency with a red and swollen right
foot
• Apyrexial and haemodynamically stable
• Diagnosed with type 2 diabetes two years
earlier
• Oral hypoglycaemic therapy: blood sugar
control moderate
Investigations
• X-ray of the foot showed changes
consistent with both osteomyelitis and soft
tissue infection
• C-reactive protein 219 mg/l (<10mg/l)
• Neutrophils 19.2 x109/l (4-11 x109/l)
• Plasma glucose 24.6 mmol/l (3-6 mmo/l).
Illustration reproduced with permission from Clinical Publishing Ltd, Oxford
Diagnosis & Initial management
• Moderate diabetic foot infection
– limb-threatening
– critical ischaemia not present
• Treated empirically with IV vancomycin
and piperacillin/tazobactam
Microbiological investigation
• Polymicrobial infection
– Gram stain of pus showed neutrophils, Gram
positive cocci and Gram positive bacilli
– Enterocoocci and alpha-haemolytic
Streptoccoci were isolated from pus
– At least five different species comprising
Gram positive cocci and Enterobacteria were
cultured from superficial swabs.
Surgical Intervention
• On day 4 debridement was undertaken to
remove infected bone and soft tissue
• Enterococcus faecalis, Propionobacterium
sp. and Escherichia coli were isolated from
deep pus and tissue samples.
Further management
• On day 7 antimicrobial therapy was
changed to oral amoxicillin plus
ciprofloxacin.
• 4 weeks of antimicrobial therapy were
given in total
• Ongoing wound and foot care was
provided by the Podiatry team
Diabetic foot infection
• Most common reason for diabetes-related
admission to hospital
• High morbidity – may result in amputations
Why does DFI occur?
• Foot ulceration is the major factor and
occurs secondary to peripheral neuropathy
and/or vascular insufficiency (neuroischaemic foot ulceration)
• Hyperglycaemia and other metabolic
disturbances contribute through
immunological (e.g. neutrophil)
dysfunction and poor wound healing
Prevention of DFI
• Appropriate foot care/pressure relief
– Podiatry services
• Good glycaemic control
– Specialist diabetes services
CID 2004; 39:885-910
Multidisciplinary Foot-care Team
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Physician
Podiatrist
Medical Microbiologist/ID Physician
Vascular surgeon
Foot surgeon
Radiologist
Microbiological Samples
• Samples should be collected following cleansing
and debridement
• Deep soft tissue samples should be obtained
from the base of an ulcer by curettage, or at
surgery
• Bone biopsy (including histopathological
examination) is important in establishing a
diagnosis of osteomyelitis
• Samples should be transported without delay to
the laboratory and cultured under both aerobic
and anaerobic conditions.
Microbiological pathogens
Infection is typically polymicrobial where
ulceration is present
• Aerobic Gram positive cocci
– Staphylococcus aureus
– Β-haemolytic streptococci
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Enterococci
Enterobacteriaceae
Obligate anaerobes
(Nonfermentative Gram negative rods)
(Candida spp.)
Diagnosis and Assessment
• DFI is diagnosed clinically by signs and
symptoms of inflammation
• Infections are categorized as mild, moderate or
severe, on the basis of clinical and laboratory
features
• Assessment is made as to whether an episode
is life or limb threatening
Categorization helps to guide appropriate clinical
management
Mild infection
Purulent or inflamed wound present
• Limited to skin and superficial soft tissues
• Inflammation extends <2cm from wound
• Not systemically unwell
Treatment usually by oral route
e.g. flucloxacillin, doxycycline, clindamycin
Microbiological sampling not routinely required for mild
infection unless recent antimicrobial therapy or previous
antibiotic-resistant organisms
Moderate infection
Purulent or inflamed wound present in a patient who is
systemically well and/or one of the following
• inflammation extends >2cm from wound
• lymphangitis
• spread beneath superficial fascia
• abscess formation
• necrosis or gangrene
• involvement of muscle, tendon, joint or bone
Treatment by oral or parenteral routes according to clinical
assessment and choice of agent
Moderate infection
Treatment options include
• amoxicillin/clavulanate
• clindamycin + ciprofloxacin
• rifampicin + levofloxacin
• piperacillin/tazobactam
• ertapenem
NB. Choices influenced by local policy with consideration of
local issues such as C. difficile and MRSA incidence
Add glycopeptide, linezolid or daptomycin if MRSA infection
is suspected or infection is life/limb-threatening
Severe infection
Infection in a patient with evidence of systemic
inflammatory response syndrome
IV treatment, at least initially, as an inpatient, e.g.
• clindamycin + ciprofloxacin
• piperacillin/tazobactam
• meropenem or imipenem/cilastatin
Add glycopeptide, linezolid or daptomycin if MRSA infection
is suspected or infection is life/limb-threatening
Duration of Antimicrobial Therapy
• Continued until the signs and symptoms of
infection have resolved (ulcer may persist)
• Mild soft tissue infections 1-2 weeks
• Moderate-severe soft tissue 3-4 weeks
Osteomyelitis typically 6 weeks, unless all
affected bone is completely removed by surgery
(1-2 weeks)
• Therapy ≥3 months sometimes required for
extensive bone infection e.g. calcaneum
NB. Courses may need to be longer than for
non-diabetic patients with cellulitis
Antibiotics in DFI
• Antimicrobial therapy can be challenging!
• Consider patient factors (e.g. age, renal
function, peripheral vascular disease)
• Side effects are common
– Gastrointestinal intolerance of oral antibiotics,
often to multiple agents
– Hypersensitivity reactions (typically skin
rashes)
• Deterioration in renal function may occur
Does the patient require surgery?
Surgical intervention is often required. Urgent
assessment is needed by a surgeon with
expertise in foot surgery where the infection is
life- or limb-threatening. Vascular surgery may
be needed where there is critical ischaemia.
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Excision & drainage
Debridement
Resection +/- reconstruction
Revascularisation
Amputation
Wound Care Issues
• Ongoing debridement of non-viable
tissue as required
• Dressings to allow daily inspection of
wound and to encourage a moist
wound-healing environment
• Remove pressure from the wound
(off-loading)
Glucose Control
Good blood glucose control should be
achieved
• To manage the acute infection
• To reduce the risk of future foot problems
Diagnostic Imaging 1
• Imaging should always be considered to identify
soft tissue abscesses or osteomyelitis
• Osteomyelitis is present in 30% DFI
• It is important to identify underlying osteomyelitis
as this influences the choice, dose, route and
duration of antimicrobial therapy, however
• There is no single, non-invasive, highly sensitive
and specific test for osteomyelitis
Diagnostic Imaging 2
• If osteomyelitis is suspected and initial Xray does not confirm the presence of
osteomyelitis, use magnetic resonance
imaging (MRI).
• If MRI is contraindicated, white blood cell
(WBC) scanning may be performed
instead
NICE clinical guideline 119
Clinical signs of osteomyelitis
The following are associated with
osteomyelitis
• Inflamed, swollen (‘sausage’) toe
• Presence of exposed bone
• Positive ‘probe-to-bone’ test
‘Sausage toe’
Osteomyelitis of hallux
Probe to bone?
X-rays and DFI
• Plain X-rays can be negative during the first 2-3
weeks of osteomyelitis
• Charcot neuroarthropathy & gout may produce
similar appearances
• Pragmatic approach where osteomyelitis is
suspected but X-rays are negative
– treat for osteomyelitis for two weeks then re-Xray
– extend the course of therapy if new changes become
apparent.
Osteomyelitis distal phalanx
MR imaging and DFI
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Marrow oedema
Cortical discontinuity
periosteal reaction
debris
sequestra
soft tissue oedema/induration
joint involvement
ulceration
sinus formation
abscess collection
Osteomyelitis of calcaneum, T1 image
Marrow oedema
Sinus
Image courtesy of Dr J Harris, Radiology Department, Salford Royal Hospital
Osteomyelitis of 1st metatarsal head, STIR image
Soft tissue oedema
Marrow oedema
Image courtesy of Dr J Harris, Radiology Department, Salford Royal Hospital
OPAT and DFI
Outpatient (or home) parenteral
antimicrobial therapy may be appropriate
as prolonged IV therapy often needed for
• Severe infection
• Osteomyelitis
• MRSA infection
• Intolerance of oral agents
• No response to oral agents
Patient eligibility for OPAT
• Medically stable
• Appropriate IV access
• Home circumstances appropriate
– Support
– Communications
– Facilities
PICC lines