1. Do Physicians Find Our AST Reports As Confusing As We Do? Louis B. Rice, M.D. Louis Stokes Cleveland VA Medical Center and Case Western Reserve University Cleveland, Ohio

2. Purpose of Study To determine whether the results generated by Microbiology laboratory are easily interpretable by medical staffTo determine whether the results generated by Microbiology laboratory are easily interpretable by medical staff To determine whether microbiologic concepts inherent in some of our reports (and assumptions) are understood by practicing cliniciansTo determine whether microbiologic concepts inherent in some of our reports (and assumptions) are understood by practicing clinicians

3. Methods Fourteen item questionnaire administered to physicians at various levels in two Cleveland hospitalsFourteen item questionnaire administered to physicians at various levels in two Cleveland hospitals Personal information requested, but not requiredPersonal information requested, but not required Individual results available on requestIndividual results available on request

4. Disclaimers This is not a scientifically validated studyThis is not a scientifically validated study This is not a random sample of Medical StaffThis is not a random sample of Medical Staff

5. Acknowledgement This survey was developed, administered and analyzed with the indispensable and highly professional assistance of Klara Papp, Ph.D.This survey was developed, administered and analyzed with the indispensable and highly professional assistance of Klara Papp, Ph.D.

7. Question #1 A Minimal Inhibitory Concentration (MIC) is defined as: A. The minimal concentration of an antibiotic required to kill the test organism B. The minimal concentration of an antibiotic required to prevent growth of a standard inoculum of test organisms C. The minimal concentration of an antibiotic achievable in human serum D. The minimal concentration of an antibiotic achievable in human urine 90% 9% 1%

8. Question #2 What is a breakpoint? A. The concentration of an antibiotic required to inhibit growth of an organism in vitro B. The concentration of an antibiotic that becomes toxic to human tissues C. The MIC determined to represent a high likelihood for successful treatment of a bacterial strain with a specific antibiotic 5% 25% 68%

9. Question #3 Who defines the breakpoints for different antibiotics? A. The American Society for Microbiology B. The Food and Drug Administration C. The National Committee for Clinical Laboratory Standards D. The American College of Physicians 16% 37% 45% 1%

10. Question #4 Important considerations in determining breakpoints for specific antibiotics include: A. Achievable serum concentrations of the antibiotic B. The pharmacokinetics of the antibiotic C. The pharmacodynamics of antibiotic-organism interactions in animal studies D. All of the above 14% 1% 84%

12. Question #5 Is the Klebsiella oxytoca susceptible to meropenem? A. Yes B. No

13. Bacteriology Final Report – K. oxytoca AntibioticSusceptibilityInterpretation Amikacin <= 2 S Ampicillin >= 32 R Cefazolin R Ceftazidime>=32R Trimethoprim-sulfa>=320R Meropenem <= 2 S Gentamicin >= 16 R Ampicillin/sulbactam >= 32 R Levofloxacin4I CefotetanII Cefepime <= 4 S Piperacillin/tazobactam64I

14. Question #5 Is the Klebsiella oxytoca susceptible to meropenem? A. Yes B. No 95% 3%

15. Question #7 What is the breakpoint for Pseudomonas aeruginosa resistance to ceftazidime? A. >=8 B. >=32 C. Insufficient information

16. Bacteriology Final Report – P. aeruginosa AntibioticSusceptibilityInterpretation AmikacinSS Ampicillin Cefazolin CeftazidimeSS Trimethoprim-sulfaRR MeropenemRR GentamicinRR Ampicillin/sulbactam LevofloxacinRR Cefotetan CefepimeSS Piperacillin/tazobactamSS

17. Question #7 What is the breakpoint for Pseudomonas aeruginosa resistance to ceftazidime? A. >=8 B. >=32 C. Insufficient information 7% 14% 77%

18. Question #8 Under what circumstances would the results of the enterococcal synergy testing shown in this report be useful? A. For the treatment of urinary tract infection B. For the treatment of infections in which Gram negative bacilli are also involved C. For the treatment of endocarditis D. Synergy testing is never useful 20% 8% 64% 6%

19. Question #9 The K. oxytoca is of intermediate susceptibility to both levofloxacin and piperacillin-tazobactam. However, the MIC for levofloxacin is 4 and piperacillin-tazobactam 64. Does this mean that levofloxacin will be a more effective therapeutic agent in this case? A. Yes B. No 22% 74%

20. Answers to Why Most commented appropriately on achievable serum levels, etc.Most commented appropriately on achievable serum levels, etc. “It takes more dilutions of pip-tazo to lose its effectiveness than levofloxacin”“It takes more dilutions of pip-tazo to lose its effectiveness than levofloxacin” “MIC determines dose, not susceptibility”“MIC determines dose, not susceptibility” “Other factors are relevant such as…likelihood of developing further resistance”“Other factors are relevant such as…likelihood of developing further resistance”

21. Question #10 In what type of infection could you use levofloxacin with greatest confidence against this strain of K. oxytoca? A. Abdominal abscess B. Aspiration pneumonia C. Urinary tract infection D. Osteomyelitis 9% 9% 2% 75% 7%

22. Answers to Why Most commented appropriately on achievable urine levelsMost commented appropriately on achievable urine levels

24. Question #12 Is the Pantoea strain described above susceptible to cefotetan? A. Yes B. No

25. Bacteriology Final Report - Pantoea AntibioticSusceptibilityInterpretation Ampicillin >= 32 R Cefazolin R Ceftazidime>=32R Trimethoprim-sulfa<=10S Meropenem <= 2 S Gentamicin <= 0.05 S Ampicillin/sulbactam >= 32 R Levofloxacin <= 1 S Cefotetan32I Cefepime <= 4 S Piperacillin/tazobactam32I

26. Question #12 Is the Pantoea strain described above susceptible to cefotetan? A. Yes B. No 44% 52% 52%

27. Bacteriology Final Reports – E. cloacae Antibiotic First Culture Second Culture Ampicillin >= 32, R Cefazolin Ceftazidime <=8, S >= 32, R Trimethoprim-sulfa <=10, S Meropenem <= 2, S Gentamicin <= 0.5, S Ampicillin/sulbactam >= 32, R Levofloxacin <= 1, S Cefotetan >= 64, R Cefepime <= 4, S Piperacillin/tazobactam 32, I >= 128, R

28. Question #13 The above culture was taken one week after the culture shown earlier. Is it likely that the Enterobacter isolates represent the same strain from two different cultures? A. Yes, because both are susceptible to cefepime. B. No, because their susceptibilities to piperacillin-tazobactam and ceftazidime differ. C. They could be the same or different. You cannot tell without performing more detailed genetic studies. 16% 9% 70%

29. Question #14 What is the breakpoint for cefotetan resistance for the Enterobacter cloacae? A. 32 B. 64 C. 128

30. Breakpoint for Cefotetan Enterobacter cloacae Pantoeae SuscIntpSuscIntp Cefotetan >= 64 R32I

31. Question #14 What is the breakpoint for cefotetan resistance for the Enterobacter cloacae? A. 32 B. 64 C. 128 61% 18% 13%

33. Random Comments I know I need to review this – how embarrassing!I know I need to review this – how embarrassing! Note to Dr. Rice: You’re right! We do learn too much cardiology and not enough ID in our programNote to Dr. Rice: You’re right! We do learn too much cardiology and not enough ID in our program

34. Conclusions Clinicians are more adept at interpreting Microbiology laboratory reports than we give them credit forClinicians are more adept at interpreting Microbiology laboratory reports than we give them credit for The subtleties of antimicrobial testing are understood by most medical staff under the conditions of this testThe subtleties of antimicrobial testing are understood by most medical staff under the conditions of this test However, this understanding is not complete, and will benefit from expert Infectious Diseases input in complicated casesHowever, this understanding is not complete, and will benefit from expert Infectious Diseases input in complicated cases