Presentation on theme: "Diabetic foot infection"— Presentation transcript:
1 Diabetic foot infection Dr Paul ChadwickConsultant MicrobiologistSalford Royal Hospital
2 Case HistoryA 76 year old man was admitted as an emergency with a red and swollen right footApyrexial and haemodynamically stableDiagnosed with type 2 diabetes two years earlierOral hypoglycaemic therapy: blood sugar control moderate
3 InvestigationsX-ray of the foot showed changes consistent with both osteomyelitis and soft tissue infectionC-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).
4 X-ray changes include destruction of the metatarso-phalangeal joint of the great toe associated with lucencies within the soft tissues extending across the second third and fourth toes and irregularity of the head of the second and third metatarsals suggesting associated fracture.Illustration reproduced with permission from Clinical Publishing Ltd, Oxford
5 Diagnosis & Initial management Moderate diabetic foot infectionlimb-threateningcritical ischaemia not presentTreated empirically with IV vancomycin and piperacillin/tazobactam
6 Microbiological investigation Polymicrobial infectionGram stain of pus showed neutrophils, Gram positive cocci and Gram positive bacilliEnterocoocci and alpha-haemolytic Streptoccoci were isolated from pusAt least five different species comprising Gram positive cocci and Enterobacteria were cultured from superficial swabs.
7 Surgical Intervention On day 4 debridement was undertaken to remove infected bone and soft tissueEnterococcus faecalis, Propionobacterium sp. and Escherichia coli were isolated from deep pus and tissue samples.
8 Further managementOn day 7 antimicrobial therapy was changed to oral amoxicillin plus ciprofloxacin.4 weeks of antimicrobial therapy were given in totalOngoing wound and foot care was provided by the Podiatry team
9 Diabetic foot infection Most common reason for diabetes-related admission to hospitalHigh morbidity – may result in amputations
10 Why does DFI occur?Foot ulceration is the major factor and occurs secondary to peripheral neuropathy and/or vascular insufficiency (neuro-ischaemic foot ulceration)Hyperglycaemia and other metabolic disturbances contribute through immunological (e.g. neutrophil) dysfunction and poor wound healing
14 Multidisciplinary Foot-care Team PhysicianPodiatristMedical Microbiologist/ID PhysicianVascular surgeonFoot surgeonRadiologistEssential to have interested specialists who can be accessed quickly to provide optimal care and avoid unnecessary amputation
15 Microbiological Samples Samples should be collected following cleansing and debridementDeep soft tissue samples should be obtained from the base of an ulcer by curettage, or at surgeryBone biopsy (including histopathological examination) is important in establishing a diagnosis of osteomyelitisSamples should be transported without delay to the laboratory and cultured under both aerobic and anaerobic conditions.
16 Microbiological pathogens Infection is typically polymicrobial where ulceration is presentAerobic Gram positive cocciStaphylococcus aureusΒ-haemolytic streptococciEnterococciEnterobacteriaceaeObligate anaerobes(Nonfermentative Gram negative rods)(Candida spp.)
17 Diagnosis and Assessment DFI is diagnosed clinically by signs and symptoms of inflammationInfections are categorized as mild, moderate or severe, on the basis of clinical and laboratory featuresAssessment is made as to whether an episode is life or limb threateningCategorization helps to guide appropriate clinical management
18 Mild infection Purulent or inflamed wound present Limited to skin and superficial soft tissuesInflammation extends <2cm from woundNot systemically unwellTreatment usually by oral routee.g. flucloxacillin, doxycycline, clindamycinMicrobiological sampling not routinely required for mild infection unless recent antimicrobial therapy or previous antibiotic-resistant organismsTherapy aimed against aerobic GPC is usually adequate for mild infections
19 Moderate infectionPurulent or inflamed wound present in a patient who is systemically well and/or one of the followinginflammation extends >2cm from woundlymphangitisspread beneath superficial fasciaabscess formationnecrosis or gangreneinvolvement of muscle, tendon, joint or boneTreatment by oral or parenteral routes according to clinical assessment and choice of agent
20 Moderate infection Treatment options include amoxicillin/clavulanate clindamycin + ciprofloxacinrifampicin + levofloxacinpiperacillin/tazobactamertapenemNB. Choices influenced by local policy with consideration of local issues such as C. difficile and MRSA incidenceAdd glycopeptide, linezolid or daptomycin if MRSA infection is suspected or infection is life/limb-threateningTherapy aimed against aerobic GPC may be adequate for moderate infections in patients who have not received prior antibiotics
21 Severe infectionInfection in a patient with evidence of systemic inflammatory response syndromeIV treatment, at least initially, as an inpatient, e.g.clindamycin + ciprofloxacinpiperacillin/tazobactammeropenem or imipenem/cilastatinAdd glycopeptide, linezolid or daptomycin if MRSA infection is suspected or infection is life/limb-threateningBroad-spectrum therapy pending culture results
22 Duration of Antimicrobial Therapy Continued until the signs and symptoms of infection have resolved (ulcer may persist)Mild soft tissue infections 1-2 weeksModerate-severe soft tissue 3-4 weeksOsteomyelitis 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. calcaneumNB. Courses may need to be longer than for non-diabetic patients with cellulitis
23 Antibiotics in DFI Antimicrobial therapy can be challenging! Consider patient factors (e.g. age, renal function, peripheral vascular disease)Side effects are commonGastrointestinal intolerance of oral antibiotics, often to multiple agentsHypersensitivity reactions (typically skin rashes)Deterioration in renal function may occurDeterioration in renal function may be seen with glycopeptides, doxycycline or ciprofloxacinAll hospitals should have an antibiotic guideline for DFI (NICE)
24 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.Excision & drainageDebridementResection +/- reconstructionRevascularisationAmputationImportant to get an enthusiastic surgeon on board as part of the multidisciplinary team
25 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 environmentRemove pressure from the wound (off-loading)Debridement with a scalpel can often be undertaken without anaesthetic in patients with a neuropathic foot.Many wound care products available – limited evidence to favour any particular dressing type.
26 Glucose Control Good blood glucose control should be achieved To manage the acute infectionTo reduce the risk of future foot problemsInvolvement of specialist diabetes nurses is helpful
27 Diagnostic Imaging 1Imaging should always be considered to identify soft tissue abscesses or osteomyelitisOsteomyelitis is present in 30% DFIIt is important to identify underlying osteomyelitis as this influences the choice, dose, route and duration of antimicrobial therapy, howeverThere is no single, non-invasive, highly sensitive and specific test for osteomyelitisMRI is the most accurate of the available radiological tests, but difficult to distinguish infection from Charcot neuropathy
28 Diagnostic Imaging 2If osteomyelitis is suspected and initial X-ray does not confirm the presence of osteomyelitis, use magnetic resonance imaging (MRI).If MRI is contraindicated, white blood cell (WBC) scanning may be performed insteadNICE clinical guideline 119
29 Clinical signs of osteomyelitis The following are associated with osteomyelitisInflamed, swollen (‘sausage’) toePresence of exposed bonePositive ‘probe-to-bone’ test
30 Suggests osteomyelitis (but not conclusive) ‘Sausage toe’
31 Osteomyelitis of hallux Probe to bone?Bone may either be visible in the base of an ulcer, or it may be possible to touch bone directly using a blunt metal probe. Either is suggestive of osteomyelitis (but not conclusive).
32 X-rays and DFIPlain X-rays can be negative during the first 2-3 weeks of osteomyelitisCharcot neuroarthropathy & gout may produce similar appearancesPragmatic approach where osteomyelitis is suspected but X-rays are negativetreat for osteomyelitis for two weeks then re-Xrayextend the course of therapy if new changes become apparent.
33 Osteomyelitis distal phalanx Distal phalanx (2 different views) shows bone loss, cortical irregularity and disordered bone architecture, consistent with osteomyelitis. Note 50% of bone has to be lost before this is apparent on plain Xray.
35 Osteomyelitis of calcaneum, T1 image Marrow oedemaSinusImage courtesy of Dr J Harris, Radiology Department, Salford Royal Hospital
36 Osteomyelitis of 1st metatarsal head, STIR image Soft tissue oedemaMarrow oedemaImage courtesy of Dr J Harris, Radiology Department, Salford Royal Hospital
37 OPAT and DFIOutpatient (or home) parenteral antimicrobial therapy may be appropriate as prolonged IV therapy often needed forSevere infectionOsteomyelitisMRSA infectionIntolerance of oral agentsNo response to oral agentsExamples of drugs used: teicoplanin, daptomycin, ertapenem, meropenem
38 Patient eligibility for OPAT Medically stableAppropriate IV accessHome circumstances appropriateSupportCommunicationsFacilities