Do Physicians Find Our AST Reports As Confusing As We Do?

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 staff • To 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 hospitals • Personal information requested, but not required • Individual results available on request

4. Disclaimers • This is not a scientifically validated study • This 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.

7. 9% 90% 1% 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

8. 25% 5% 68% 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

9. 37% 16% 45% 1% 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

10. 14% 1% 84% 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

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

13. Bacteriology Final Report – K. oxytoca

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

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

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

18. 8% 20% 64% 6% 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

19. 22% 74% 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

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

21. 2% 9% 75% 7% 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

22. Answers to Why • Most 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

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

27. Bacteriology Final Reports – E. cloacae

28. 9% 16% 70% 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.

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

30. Breakpoint for Cefotetan

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

33. Random Comments • 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 program

34. Conclusions • Clinicians 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 test • However, this understanding is not complete, and will benefit from expert Infectious Diseases input in complicated cases