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Using CLSI M45-A2 for Antimicrobial Susceptibility Testing of Infrequently-isolated Organisms

Erik Munson. Clinical Microbiology Wheaton Franciscan Laboratory Wauwatosa, Wisconsin. Using CLSI M45-A2 for Antimicrobial Susceptibility Testing of Infrequently-isolated Organisms. The presenter states no conflict of interest and has no financial relationship

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Using CLSI M45-A2 for Antimicrobial Susceptibility Testing of Infrequently-isolated Organisms

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  1. Erik Munson Clinical Microbiology Wheaton Franciscan Laboratory Wauwatosa, Wisconsin Using CLSI M45-A2 for Antimicrobial Susceptibility Testing of Infrequently-isolated Organisms The presenter states no conflict of interest and has no financial relationship to disclose relevant to the content of this presentation.

  2. OUTLINE • M45-A2 guideline • A. Appropriate format • B. Microbiology review • Caveats and other intelligence for your life • A. Clinical presentation • B. Taxonomy • C. Antibiogram

  3. BRIEF HISTORY M45-A2 Methods for Antimicrobial Dilution and Disk Susceptibility Testing of Infrequently Isolated or Fastidious Bacteria; Approved Guideline-- Second Edition (2010) M45-A Ibid (2006) M45-P Ibid (2005)

  4. You Make the Call

  5. QUESTION ONE Can the microbiology laboratory perform antimicrobial susceptibility testing on Abiotrophia spp.? A. No B. Possibly C. Yes; John Tesh advised us how D. Yes; the microbiology laboratory is omniscient E. What *#$% is Abiotrophia spp.

  6. Abiotrophia spp.; Granulicatella spp.

  7. NOTES Former nutritionally-deficient, -variant streptococci; requires cysteine or pyridoxal for growth Koneman, 5th ed. Testing of isolates from normally-sterile sources may be warranted, especially in immunodeficient patients Interpretive criteria derived from Streptococcus spp. breakpoints (CLSI M100 series) Diminished susceptibility to penicillin CLSI M45-A2

  8. LIMITED DATA 46.7% susceptibility to macrolide agents J. Clin. Microbiol. 42: 4323-4326; 2004 Diagn. Microbiol. Infect. Dis. 38: 189-191; 2000

  9. You Make the Call

  10. CASE PRESENTATION 29-year-old female wading in Milwaukee River; fell and scraped knee on rock Visited ER for cleaning & suturing; no antibiotics Pain worsened overnight; came back to ER Septic pre-patellar bursitis; surgical debridement WBC 24,200/mL (89.0% segmented neutrophils) Sutures removed to reveal purulent discharge

  11. QUESTION TWO What is the most likely infectious etiology for this clinical presentation? A. Methicillin-susceptible Staphylococcus aureus B. Aeromonas species C. Non-tuberculous Mycobacterium species D. Pseudomonas aeruginosa E. A 24,000 white count doesn’t really alarm me.

  12. A. hydrophila complex; P. shigelloides

  13. NOTES Aeromonas caviae complex Aeromonas hydrophila complex Aeromonas veronii complex (incl. biovar sobria) Plesiomonas shigelloides Aeromonas spp. resistant to ampicillin Ampicillin resistance in P. shigelloides unclear Often limited to isolates from extraintestinal sites Interpretive criteria derived from Enterobacteriaceae breakpoints (CLSI M100 series) CLSI M45-A2

  14. Bacillus spp.

  15. NOTES Not Bacillus anthracis Interpretive criteria derived from Staphylococcus spp. breakpoints (CLSI M100 series) Testing of isolates from normally-sterile sources may be warranted, especially in immunodeficient patients Generally resistant to penicillins and cephems; b-lactamase testing is unreliable CLSI M45-A2

  16. LIMITED DATA Antimicrob. Agents Chemother. 32: 642-645; 1988

  17. Campylobacter jejuni/coli

  18. NOTES Microaerophilic (10% CO2, 5% O2, 85% N2) Compressed gas incubator Microaerophilic gas-generating sachets Sealed plastic bags/pouches not reproducible Ciprofloxacin, tetracycline interpretive criteria derived from Enterobacteriaceae breakpoints (CLSI M100 series); population distributions Testing may be useful for epidemiology or for patients with protracted or severe symptoms CLSI M45-A2

  19. DATA Emerg. Infect. Dis. 8: 1501-1503; 2002

  20. You Make the Call

  21. QUESTION THREE Can the microbiology laboratory perform antimicrobial susceptibility testing on diphtheroids? A. No B. Possibly C. Yes; John Tesh advised us how D. Yes; the microbiology laboratory is omniscient E. Do we really want to advertise this?

  22. Corynebacterium spp.; CORYNEFORMS

  23. NOTES All Corynebacterium spp. Leifsonia spp. Arcanobacterium spp. Microbacterium spp. Brevibacterium spp. Oerskovia spp. Cellulomonas spp. Rothia spp. Dermabacter spp. Turicella spp. Testing of isolates from normally-sterile sources may be warranted, especially in immunodeficient patients Some Corynebacterium spp. resistant to multiple drug classes CLSI M45-A2

  24. MORE NOTES Interpretations of “resistant” may be reported at 24 hours; isolates appearing “susceptible” to b- lactam agents are re-incubated to be read @ 48h Derivations of interpretive criteria (CLSI M100) Cephems from Streptococcus spp. Linezolid from Enterococcus spp. Penicillin, erythromycin from population distributions Rest from Staphylococcus spp. CLSI M45-A2

  25. Erysipelothrix rhusiopathiae

  26. NOTES Looks like a-hemolytic streptococci H2S-positive Testing not necessarily required ID may be more important in context of potentially fulminant endocarditis (d/c empiric therapy covering Gram-positives) Erythromycin and clindamycin testing may be warranted in patients with penicillin allergy gefor.4t.com CLSI M45-A2

  27. MORE NOTES Intrinsic resistance to vancomycin (PELL) Derivations of interpretive criteria (CLSI M100) Ciprofloxacin from Staphylococcus spp. Rest from Streptococcus spp. CLSI M45-A2

  28. Hs & As Haemophilus aphrophilus Haemophilus paraphrophilus Haemophilus segnis A. actinomycetemcomitans Aggregatibacter spp.

  29. (HA)CEK GROUP

  30. NOTES Aggregatibacter spp. Eikenella corrodens Cardiobacterium spp. Kingella spp. Testing of isolates from normally-sterile sources may be warranted, especially in immunodeficient patients or those unable to tolerate PO b-lactams Testing of E. corrodens isolates from bite wounds may not be necessary due to high probability of susceptibility to amoxicillin-clavulanic acid CLSI M45-A2

  31. MORE NOTES b-lactamase production predicts (most) ampicillin resistance (exception: Aggregatibacter spp.) Watch growth control wells; could be problematic Derivations of interpretive criteria (CLSI M100) Chloramphenicol from Streptococcus spp. Penicillin from population distributions Rest from Haemophilus influenzae CLSI M45-A2

  32. Helicobacter pylori

  33. Lactobacillus spp.

  34. NOTES Testing of isolates from normally-sterile sources may be warranted Derivation of interpretive criteria (CLSI M100) Gentamicin, linezolid, vancomycin from Staphylococcus spp. Clindamycin, imipenem from population distributions Rest from Enterococcus spp. Intrinsic resistance to vancomycin (PELL), particularly those that grow well in ambient air CLSI M45-A2

  35. LIMITED DATA Antimicrob. Agents Chemother. 34: 543-549; 1990

  36. Leuconostoc spp.

  37. NOTES Interpretive criteria only provided for penicillin, ampicillin, gentamicin, chloramphenicol, minocycline Intrinsicresistance to vancomycin (PELL) Testing of isolates from normally-sterile sources may be warranted (e.g., endocarditis) Interpretive of interpretive criteria (CLSI M100) Gentamicin from Staphylococcus spp. Rest from Enterococcus spp. CLSI M45-A2

  38. LIMITED DATA Antimicrob. Agents Chemother. 34: 543-549; 1990

  39. Listeria monocytogenes

  40. NOTES Ampicillin and penicillin data previously published (CLSI M100-S15; 2005) Trimethoprim-sulfamethoxazole interpretive criteria derived from Streptococcus spp. breakpoints (CLSI M100 series) Testing of isolates may be limited to suspected treatment failures or patients with penicillin allergy Intrinsically resistant to cephems CLSI M45-A2

  41. Moraxella catarrhalis

  42. NOTES b-lactamase production predicts ampicillin and amoxicillin resistance Derivation of interpretive criteria (CLSI M100) Macrolides from population distributions Rest from Haemophilus spp. Testing may be useful for epidemiology or for patients with protracted or severe infections CLSI M45-A2

  43. DATA J. Clin. Microbiol. 44: 3775-3777; 2006

  44. You Make the Call

  45. CASE PRESENTATION 55-year-old female bitten by family cat on R palm; progressive erythema over next 12-18 hours Afebrile upon presentation Slightly tachycardic and tachypneic WBC 12,100/mL (77.8% segmented neutrophils) Empiric ampicillin-sulbactam Gram-negative bacillus; no growth MacConkey Susceptible to penicillin Discharge on hospital day 3

  46. QUESTION FOUR What is the most likely infectious etiology for this clinical presentation? A. Viridans group Streptococcus B. CDC group EF-4a C. Pasteurella species D. A strictly veterinary pathogen E. I’m doomed. Help me, John Tesh!!!

  47. Pasteurella spp.

  48. NOTES Routine testing usually not necessary on isolates from bite wounds; empiric therapy for polymicrobial infection Testing of isolates from normally-sterile sources may be warranted, especially in immunodeficient patients Interpretive criteria derived from population distributions b-lactamase testing can have value; rare isolates with penicillin, amoxicillin MIC > 0.5 mg/mL CLSI M45-A2

  49. Pediococcus spp.

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