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I.D. Pearls 2010

I.D. Pearls 2010. James R. Johnson, MD VA Medical Center University of Minnesota Minneapolis, MN. What I Will Cover…. Antibiotic Armageddon Basic principles Common fake-outs Myths and urban legends Tools of the trade Blood cultures, culture reports Specific conditions Diabetic foot

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I.D. Pearls 2010

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  1. I.D. Pearls 2010 James R. Johnson, MD VA Medical Center University of Minnesota Minneapolis, MN

  2. What I Will Cover… • Antibiotic Armageddon • Basic principles • Common fake-outs • Myths and urban legends • Tools of the trade • Blood cultures, culture reports • Specific conditions • Diabetic foot • Staph. aureus bacteremia • Cellulitis • C. difficile

  3. We are here Antibiotic Armageddon New Antimicrobials Resistance Year

  4. 2003

  5. New drugs No drugs “E.S.C.A.P.E.” Bugs • Enterococcusfaecium • Staph. aureus (MRSA) • Clostridium difficile • Acinetobacter baumanii (MDR) • Pseudomonas (MDR) • Enterobacteriaciae (MDR)

  6. Basic Principles • Define the pathogen • Any culture (from relevant site) beats none • Contact outside labs for early culture results • Reculture if new fever (etc.), new abx • Treat the patient, not the culture • Match aggressiveness of Rx to severity and tempo of disease • Source control • Drain, debride, discontinue devices • Imaging, interventionalists

  7. Basic Principles (cont.) • Antibiotics are not always benign; use with care • Allergy and ADEs (rash, GI, fever, cytopenias, renal, etc.) • Drug-drug interactions • TMP-SMZ, FQs, flagyl + warfarin --> high INR, bleeding • Linezolid + SSRIs --> seretonin syndrome • FQs, macrolides + (multiple drugs) --> long QT, torsades • FQs, doxy, mino + Ca, Mg, Al, Fe --> drug inactivation • Resistance: current bug, next bug, C. difficile, population • Treat as narrowly and briefly as possible • Contain the contagion (infection control) • Prevention (immunize, hygiene, vents & lines…)

  8. Common Fake-Outs • “Cellulitis” • Gout, stasis, dermatitis, bug bite • “Pneumonia” • Edema, effusion, atalectasis, aspiration, fibrosis, tumor, vasculitis, hypersensitivity • “UTI” • Asymptomatic bacteriuria, pyuria, vaginitis, contaminated sample

  9. Myths & Urban Legends • Taking all the antibiotics will prevent resistance • Osteomyelitis requires IV Rx • Triple-phase bone scan is good test for osteo • Antibiotic stewardship is about $, not patients • Best to double-cover Pseudomonas • Pyuria indicates clinical importance of bacteriuria • Bacteriuria should be eliminated before implants • BCs should be timed to match fever spikes • IV antibiotics are superior to PO

  10. Highly Orally Bioavailable Antimicrobials • Fluoroquinolones • Tetracyclines • Fluconazole • Metronidazole • TMP-SMZ • Clindamycin • Linezolid

  11. Highly orally bioavailable agents include: 1. TMP-SMZ 2. Gentamicin 3. Vancomycin 4. Fluconazole 5. Cephalexin 6. Metronidazole

  12. Demystifying Blood Cultures • “Set” = 2 bottles (aerobic, anaerobic) • Any bug can grow in either bottle • Sensitivity of BC • Volume, prior abx, organism, inoculum, cont. vs. intermit. • Specificity of BC • Proportion positive, organism(s), context, time to pos. • True: S. aureus, Strep, Pneumo, GNRs, Entc, yeast • False: CNS, diphtheroids, P. acnes, Bacillus, Clostridium • Variable: Strep viridans • Line vs. peripheral BC can help define source

  13. Demystifying Blood Cultures (cont.) • “R/O endocarditis” voodoo • just get 2-3 sets • Fungal BCs: are for histo, crypto, molds • Not Candida (for which routine BCs are fine) • AFB BC: AIDS, profound CMI defect • Viral BC: now replaced by (quant.) PCR • CMV, EBV, parvo B19

  14. Demystifying Culture Reports • First result reported is Gram stain (direct prep) • WBC (PMN, monos), epi’s, organisms • Next: preliminary culture result • “Catalase-pos. GPCs in prs. & clusters resembling Staph.” • “Oxidase-pos. GNRs” (code for Pseudomonas) • Then: formal ID and sensi’s; now automated • Final report may take longer, if multiple orgs. • NB: no routine sensi’s on CNS, Strep, low-count UC bugs, diphtheroids • Additional sensi’s often available; have to ask • “No PO options”--think of PO equivalents

  15. S. aureus: catalase & coag-pos. GPC

  16. Pseudomonas: oxidase-pos. GNR

  17. Common Errors in Interpreting Culture Reports • Confusing direct smear with culture • Confusing Staph. aureus with coag. neg. Staph. • Very different organisms • Very different clinical implications • Confusing MRSA, MRSE, MSSA, MSSE • Waiting for Godot (i.e., sensi’s on CNS, etc.) • Assuming culture is final when sensi’s appear on 1 organism from polymicrobial culture • Confusing bottles vs. sets (bacteremia) • Confusing UA with UC

  18. Duration of Therapy • UTI • ABU: none • Cystitis • Uncomplicated: 3d (women), 5-7d (men) • Complicated: 7-14d • Febrile UTI, pyelo, acute prostatitis: 7-14d • Chronic prostatitis: 4-12 weeks • HAP, VAP: 8d (15d if Pseudomonas) • CAP: 5-10d • Cellulitis: 5-14d • Osteo: 6 weeks

  19. Duration of Therapy (cont.) • Bacteremia • S. aureus: 14d (?10d?) - 6 weeks • CNS: 7d • Enterococcus: 14d • GNRs: 7-14d • Strep, Pneumococcus: 5-7d • COPD exacerbation: 7d • Acute Lyme, anaplasmosis: 7-10d • C. difficile: 10-14d

  20. Specific Diseases • Diabetic foot infection • Staph. aureus bacteremia • C. difficile • Cellulitis

  21. Diabetic Foot Infection • Ulcer is not an infectious disease • If clinical evidence of infection, get culture(s) • Assess severity & extent of infection • Minor, vs. limb-threatening, vs. life-threatening • Skin, soft tissues, bone, bloodstream • Flora varies (GPC, GNRs, anaerobes) • Drain, debride (amputate?), culture • May not need extended IV abx; delay PICC • Osteo not necessary to define early on • Vascularity? Neuropathy? Predisposing f’s?

  22. Staph. aureus Bacteremia

  23. Staph. aureus Bacteremia • Need to identify (i) source, (ii) metastatic foci • High-dose IV Rx; no good PO option • Daily BCs; can remain pos. w/o clinical signs • -lactams more rapidly cidal than vanco (MSSA) • Clinical impression insensitive for IE; need echo • Good quality TTE adequate? • Spine infection common; low threshold for MRI • Duration of Rx for SAB • Minimum 14d (?10d if “squeaky clean”?) • 4-6 weeks: deep focus, delayed response to Rx, ?MRSA?

  24. Percent of S. aureus that is Methicillin-Resistant 48% 24%

  25. Alternatives to Vanco for MRSA • IV • Linezolid (oxazolidinone) • Quinuprisin-dalfopristin (streptogramin) • Daptomycin (lipopeptide) • Tigecycline (glycylcycline) • Telavancin (lipoglycopeptide) • PO • TMP-SMZ (folate inhibitor) • Minocycline, doxycycline (tetracycline) • Linezolid • Clindamycin (lincosaminide)

  26. Which are superior to vanco for MRSA bacteremia? 1. Linezolid 2. Daptomycin 3. Tigecycline 4. Quinupristin-dalfopristin 5. Telavancin 6. None of the above 7. Beats me--that’s what ID is for!

  27. Cellulitis Acute gout Stasis dermatitis

  28. Cellulitis • Usually Staph. aureus or -Strep (A, B, G, C) • Reasons for non-response to PO -lactam • Insufficient drug levels (dose, absorption, non-adherence) • Host factors (vasculopathy, edema, necrosis, abscess) • Bug factors (resistance, different bug, polymicrobial) • Noninfectious (misdiagnosis) • Culture any drainage, bulla, or broken skin • Be patient; it often worsens before improving • Almost never underlying osteo (skip X-ray) • Danger signs • Disproportionate pain or toxicity; necrosis; crepitus

  29. Clostridium difficile

  30. Clostridium difficile • “The name game”: CDAD --> CDI • Diagnostic tests • Toxin insensitive; culture nonspecific & slow; ?fecal WBC? • Toxin PCR ~100% sensitive & specific; ?availability? • Therapy • Mild-moderate: PO flagyl (then PO flagyl, then PO vanco) • Severe: PO vanco, aggressive hydration • Ileus: PO vanco (high dose), IV flagyl, vanco enema, surgery • Recurrences • Prevent by avoiding antibiotics; ?probiotics? IgG? Mab? • Also: vanco taper, rifaximin chaser, fecal biotherapy (PO, PR) • Transmission: isolation, handwashing, env. decon.

  31. C. difficile Attack Rate & Outcomes Increasing primary disease Decreasing treatment success

  32. Repeated Toxin EIA Testing NPV 0.96 0.99 0.997 0.999 1.0 Assumes test SN = 73.3%, SP = 97.6%; CDI population prevalence = 10% Peterson & Robicsek. Annals 2009

  33. Which is/are true? 1. If the extremity is swollen, red, warm, and tender, the patient has cellulitis. 2. If a wound culture shows 4+ of a pathogenic organism, treatment is indicated. 3. A patient admitted for diabetic foot infection should: • undergo MRI or 3-phase bone scan to r/o osteo • receive a PICC line for extended IV Rx if osteo is found. 4. Wound cultures can be helpful despite their limited sensitivity and specificity.

  34. What I Have Covered • Antibiotic Armageddon • Basic principles • Common fake-outs • Myths and urban legends • Tools of the trade • Blood cultures, culture reports • Specific conditions • Diabetic foot • Staph. aureus bacteremia • Cellulitis • C. difficile

  35. Which is/are true? (Your call!) 1. I got some new or different ideas from this talk. 2. I disagree with some of what I heard today. 3. This talk addressed topics of practical relevance to me. 4. I would like more information about some of these topics. 5. I am likely to change my practice in some way based on things I heard today. 6. I will be more likely to consult ID in the future. 7. I will be less likely to consult ID in the future.

  36. There’s More to I.D. than…. “Pan-culture” “Vanco-Zosyn”

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