Bone and Joint Infections in Diabetics: Diagnosis and Management of Diabetic Foot and Other Common Lower Extremity Infections

Transcription

1 Bone and Joint Infections in Diabetics: Diagnosis and Management of Diabetic Foot and Other Common Lower Extremity Infections Objectives How do you to diagnose, classify and manage DFI? How do you diagnose Diabetic Foot Osteomyelitis? Is it worth collecting cultures? How do you treat DFI? Oral vs IV ABX for DFI or for DFO? When to admit to hospital? When should you refer to specialist? Does your patient need surgery? Infection risk factors in diabetics hyperglycemia Metabolic perturbations lead to neutrophile and phagocytic immune dysfunction Renal dysfunction Neuropathy Peripheral vascular disease Contiguous versus Hematogenous Hematogenous transient or sustained bacteremia seeding a bone or joint Contiguous infection starts from wound, ulcer, soft tissue focus and spreads to bone Pathogenesis of DFI contiguous spread Once in to deep tissues spreads within compartment often along a ray. Diabetic foot infection-diagnosis Based on local and systemic signs of infection Local swelling Erythema > 5mm around wound Wound tenderness or pain Warmth purulent discharge

2 International working group on diabetic foot infection (IWGDFI) Classification Scheme: Useful for decisions on management Hospitalization Surgical intervention Predicts prognosis Type 1 No Infection there must be no signs of soft tissue inflammation or purulence Type 2 - Mild Infection (type 2) only skin and superficial tissues Erythema < 2 cm No systemic symptoms Type 3 - Moderate (type 3) Infection extends to deeper tissues bone, joint, tendon, muscle Erythema > 2cm Not systemically ill Type 4 severe DFI Deep tissue involved plus systemic symptoms SIRS: HR >90; RR >20; Temp >38 or <36; WBC >12,000/ <4000 Assessment Risk Factors: when to suspect DFI Wound which can probe to bone Ulcer present >30 days Traumatic foot wound Presence of peripheral vascular disease in affected limb Previous amputation procedures Renal insufficiency Evaluation Diagnosis and Severity assessment: Patient as a whole The limb/region The ulcer and PTB test Assess arterial perfusion o Inspect o Palpate o probe Bacteriology: Bacterial species and burden not associated with infection Cultures used to guide therapy Not part of diagnosis or classification scheme Pathogen is not associated with outcome - even MRSA, VRE But inadequate therapy is associated with poor outcome

3 Should You Collect Cultures? Not if ulcer not infected If not on ABX and mild infection and low risk MDRP not needed If prior ABX, more serious infection collect - properly Culture collection technique Cleanse, debride wound then deep swab or tissue culture Cannot rely on most superficial or sinus tract specs May identify a pathogen(s) Helps rule out MRSA, MDR pathogens Culture Interpretation The clinician must know how to interpret the results Gram stain and culture quantitation can help Isolation of common pathogens is important: o MRSA o MSSA o BHS o Coliforms o Anaerobes Surgery - Indications Request surgical consult for some moderate and all severe infections Urgent intervention required for foot abscess, compartment syndrome, and all necrotizing soft tissue infections Failure to respond, progressive necrosis Surgery for OM if: o spreading/failing soft tissue infection o destroyed soft tissue envelope o progressive bone destruction on xray o bone protruding out of wound, exposed joint. o Uncorrectable ischemia Arterial Disease Macro vascular disease common May be contributing May be reversible Arterial doppler with ankle brachial indexes Vascular surgery consult CT with runoff Diabetic Foot Osteomyelitis Can be challenge to diagnose 50-60% of all hospitalized with DFI

4 10-20% of those with DFI in O/P setting Most are forefoot Many are mono-microbial Most are polymicrobial S. aureus 50% Beta-hemolytic strep 25% Coagulase Neg Staphylococcus 30% Enterobacteriaceae 40% DFO Diagnosis Histopathologic or microbiologic proof of bone infection Bone biopsy Sterile entry Core tissue Send to path and micro DFO Probable Diagnosis if: PTB elevated CRP abnormal imaging Probe to Bone Test Metal probe Gently probe wound Feel gritty raw bone Inter-operator variability high Experienced clinicians more accurate OM diagnostic Modalities All DFI should get plain Xray o bone abnormalities o Soft tissue gas o FB MRI most sensitive (90%) and specific (85%) CT may be more practical urgent test Nuc med studies o Bone scan o WBC scan :sensitivity 75-80; specificity 70-85% o WBC spect CT :sens 87.5%; specificity 71% o PET : 74%/91% DFI when to consider Hospitalization? All severe and some moderate infections Metabolic or hemodynamic instability Need broad spectrum therapy unable to provide as O/P Urgent surgical consult required Need urgent imaging or vascular studies

5 Critical foot ischemia Patient compliance and phycho-social issues Treatment DFI mild Mild, little ABX exposure Gram positives Staph aureus, BHS Beta lactams Cephalexin Amox/clav Clindamycin Treatment DFI Moderate to severe Staph aureus, beta-hemolytic strep Coliforms - if open ulcer, prior ABX exposure Anaerobes - if ischemia, tissue necrosis present Treatment DFI special germs Pseudomonas empiric Rx not needed unless risk factors present Known colonization, prior infection, water exposure, penetrating foot trauma MRSA empiric Rx if known colonization or risk factors present OR if severe infection Anaerobes yes, if grown, then treat it Treatment Broad spectrum Oral regimens Amox/clav Amox plus SXT Cefuroxime + metro Clindamycin + CIPRO Clinda +SXT or cefuroxime Moxifloxacin +/- metro Treatment IV Regimens Ceftriaxone + metro Ceftriaxone + clinda Ertapenem Pip/tazo Meropenem Factors Influencing ABX Selection for Empiric Therapy Severity of infection Bone involvement Likelihood of coliforms, anaerobes, MRSA, other MDRO s Allergies Renal function GI tract tolerance Frequency of administration Drug interactions

6 Cost C. diff potential Treatment culture directed therapy Based on a well collected specimen culture result Based on response to empiric regimen Downgrade spectrum and follow for ongoing improvement Stewardship, save money, C. diff risk OM Treatment Generally 6 weeks but very little data Many could be switched to oral after 1 or 2 weeks IV Use high bioavailable drugs clindaycin, FQ, SXT, doxycycline, metronidazole, linezolid, rifampin More prolonged therapy associated with more SE and no improve in remission DFI Management: Multidisciplinary Team Wound expert nursing care - HCN ID specialist Orthopedic surgeon Podiatry Orthotics Endocrinologist Vascular Surgeon Family physician Key References 1. Lipsky BA, Berendt AR, Cornia PB, et al Infectious Disease society of America clinical practice guidelines for the diagnosis and treatment of diabetic foot infections. Clinical Infect diseases 2012; 54; Lipsky BA, Aragon-Sanchez J, Diggle M, et al. IWGDF guidance on the diagnosis and management of foot infections in persons with diabetes. Diabetes Metabol res Rev 2016; Jan 32 suppl 1: Blume P, Wu S. Updating the Diabetic Foot Treatment Algorithm: Recommendations on Treatment Using Advanced Medicine and Therapies. Wounds 2018 Feb 30 (2);