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

Do?Do?

Louis B. Rice, M.D.Louis B. Rice, M.D.Louis Stokes Cleveland VA Medical Center Louis Stokes Cleveland VA Medical Center

and Case Western Reserve Universityand Case Western Reserve University

Cleveland, OhioCleveland, Ohio

Purpose of StudyPurpose of Study

• To determine whether the results To determine whether the results generated by Microbiology laboratory are generated by Microbiology laboratory are easily interpretable by medical staffeasily interpretable by medical staff

• To determine whether microbiologic To determine whether microbiologic concepts inherent in some of our reports concepts inherent in some of our reports (and assumptions) are understood by (and assumptions) are understood by practicing clinicianspracticing clinicians

MethodsMethods

• Fourteen item questionnaire administered Fourteen item questionnaire administered to physicians at various levels in two to physicians at various levels in two Cleveland hospitalsCleveland hospitals

• Personal information requested, but not Personal information requested, but not requiredrequired

• Individual results available on requestIndividual results available on request

DisclaimersDisclaimers

• This is not a scientifically validated studyThis is not a scientifically validated study

• This is not a random sample of Medical This is not a random sample of Medical StaffStaff

AcknowledgementAcknowledgement

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

Question #1Question #1

A Minimal Inhibitory Concentration (MIC) is defined as:A Minimal Inhibitory Concentration (MIC) is defined as:

A. The minimal concentration of an antibiotic required to kill the A. The minimal concentration of an antibiotic required to kill the test organismtest organism

B. The minimal concentration of an antibiotic required to prevent B. The minimal concentration of an antibiotic required to prevent growth of a standard inoculum of test organismsgrowth of a standard inoculum of test organisms

C. The minimal concentration of an antibiotic achievable in C. The minimal concentration of an antibiotic achievable in human serumhuman serum

D. The minimal concentration of an antibiotic achievable in D. The minimal concentration of an antibiotic achievable in human urine human urine

90%90%

9%9%

1%1%

Question #2Question #2

What is a breakpoint?What is a breakpoint?

A. The concentration of an antibiotic required to inhibit growth of A. The concentration of an antibiotic required to inhibit growth of an organism in vitroan organism in vitro

B. The concentration of an antibiotic that becomes toxic to B. The concentration of an antibiotic that becomes toxic to human tissueshuman tissues

C. The MIC determined to represent a high likelihood for C. The MIC determined to represent a high likelihood for successful treatment of a bacterial strain with a specific successful treatment of a bacterial strain with a specific antibioticantibiotic

5%5%

25%25%

68%68%

Question #3Question #3

Who defines the breakpoints for different antibiotics?Who defines the breakpoints for different antibiotics?

A. The American Society for MicrobiologyA. The American Society for Microbiology

B. The Food and Drug AdministrationB. The Food and Drug Administration

C. The National Committee for Clinical Laboratory StandardsC. The National Committee for Clinical Laboratory Standards

D. The American College of PhysiciansD. The American College of Physicians

16%16%

37%37%

45%45%

1%1%

Question #4Question #4

Important considerations in determining breakpoints for specific Important considerations in determining breakpoints for specific antibiotics include:antibiotics include:

A. Achievable serum concentrations of the antibioticA. Achievable serum concentrations of the antibiotic

B. The pharmacokinetics of the antibioticB. The pharmacokinetics of the antibiotic

C. The pharmacodynamics of antibiotic-organism interactions in C. The pharmacodynamics of antibiotic-organism interactions in animal studiesanimal studies

D. All of the aboveD. All of the above

14%14%

1%1%

84%84%

Question #5Question #5

Is the Is the Klebsiella oxytocaKlebsiella oxytoca susceptible to meropenem? susceptible to meropenem?

A. YesA. Yes

B. NoB. No

Bacteriology Final Report – Bacteriology Final Report – K. oxytocaK. oxytoca

AntibioticAntibiotic SusceptibilitySusceptibility InterpretationInterpretation

AmikacinAmikacin <= 2<= 2 SS

AmpicillinAmpicillin >= 32>= 32 RR

CefazolinCefazolin >= 32>= 32 RR

CeftazidimeCeftazidime >=32>=32 RR

Trimethoprim-sulfaTrimethoprim-sulfa >=320>=320 RR

MeropenemMeropenem <= 2<= 2 SS

GentamicinGentamicin >= 16>= 16 RR

Ampicillin/sulbactamAmpicillin/sulbactam >= 32>= 32 RR

LevofloxacinLevofloxacin 44 II

CefotetanCefotetan II II

CefepimeCefepime <= 4<= 4 SS

Piperacillin/tazobactamPiperacillin/tazobactam 6464 II

Question #5Question #5

Is the Is the Klebsiella oxytocaKlebsiella oxytoca susceptible to meropenem? susceptible to meropenem?

A. YesA. Yes

B. NoB. No

95%95%

3%3%

Question #7Question #7

What is the breakpoint for What is the breakpoint for Pseudomonas aeruginosaPseudomonas aeruginosa resistance resistance to ceftazidime?to ceftazidime?

A. >=8A. >=8

B. >=32B. >=32

C. Insufficient informationC. Insufficient information

Bacteriology Final Report – Bacteriology Final Report – P. aeruginosaP. aeruginosa

AntibioticAntibiotic SusceptibilitySusceptibility InterpretationInterpretation

AmikacinAmikacin SS SS

AmpicillinAmpicillin

CefazolinCefazolin

CeftazidimeCeftazidime SS SS

Trimethoprim-sulfaTrimethoprim-sulfa RR RR

MeropenemMeropenem RR RR

GentamicinGentamicin RR RR

Ampicillin/sulbactamAmpicillin/sulbactam

LevofloxacinLevofloxacin RR RR

CefotetanCefotetan

CefepimeCefepime SS SS

Piperacillin/tazobactamPiperacillin/tazobactam SS SS

Question #7Question #7

What is the breakpoint for What is the breakpoint for Pseudomonas aeruginosaPseudomonas aeruginosa resistance resistance to ceftazidime?to ceftazidime?

A. >=8A. >=8

B. >=32B. >=32

C. Insufficient informationC. Insufficient information

7%7%

14%14%

77%77%

Question #8Question #8

Under what circumstances would the results of the Under what circumstances would the results of the enterococcal synergy testing shown in this report be enterococcal synergy testing shown in this report be useful?useful?

A. For the treatment of urinary tract infectionA. For the treatment of urinary tract infection

B. For the treatment of infections in which Gram negative bacilli are B. For the treatment of infections in which Gram negative bacilli are also involvedalso involved

C. For the treatment of endocarditisC. For the treatment of endocarditis

D. Synergy testing is never usefulD. Synergy testing is never useful

20%20%

8%8%

64%64%

6%6%

Question #9Question #9

The The K. oxytocaK. oxytoca is of intermediate susceptibility to both is of intermediate susceptibility to both levofloxacin and piperacillin-tazobactam. However, the levofloxacin and piperacillin-tazobactam. However, the MIC for levofloxacin is 4 and piperacillin-tazobactam MIC for levofloxacin is 4 and piperacillin-tazobactam 64. Does this mean that levofloxacin will be a more 64. Does this mean that levofloxacin will be a more effective therapeutic agent in this case?effective therapeutic agent in this case?

A. YesA. Yes

B. NoB. No

22%22%

74%74%

Answers to WhyAnswers to Why

• Most commented appropriately on Most commented appropriately on achievable serum levels, etc.achievable serum levels, etc.

• ““It takes more dilutions of pip-tazo to lose It takes more dilutions of pip-tazo to lose its effectiveness than levofloxacin”its effectiveness than levofloxacin”

• ““MIC determines dose, not susceptibility”MIC determines dose, not susceptibility”

• ““Other factors are relevant such as…Other factors are relevant such as…likelihood of developing further resistance”likelihood of developing further resistance”

Question #10Question #10

In what type of infection could you use levofloxacin with In what type of infection could you use levofloxacin with greatest confidence against this strain of greatest confidence against this strain of K. oxytocaK. oxytoca??

A. Abdominal abscessA. Abdominal abscess

B. Aspiration pneumoniaB. Aspiration pneumonia

C. Urinary tract infectionC. Urinary tract infection

D. OsteomyelitisD. Osteomyelitis

9%9%

2%2%

75%75%

7%7%

Answers to WhyAnswers to Why

• Most commented appropriately on Most commented appropriately on achievable urine levelsachievable urine levels

Question #12Question #12

Is the Is the PantoeaPantoea strain described above susceptible to strain described above susceptible to cefotetan?cefotetan?

A. YesA. Yes

B. NoB. No

Bacteriology Final Report - Bacteriology Final Report - PantoeaPantoea

AntibioticAntibiotic SusceptibilitySusceptibility InterpretationInterpretation

AmpicillinAmpicillin >= 32>= 32 RR

CefazolinCefazolin >= 32>= 32 RR

CeftazidimeCeftazidime >=32>=32 RR

Trimethoprim-sulfaTrimethoprim-sulfa <=10<=10 SS

MeropenemMeropenem <= 2<= 2 SS

GentamicinGentamicin <= 0.05<= 0.05 SS

Ampicillin/sulbactamAmpicillin/sulbactam >= 32>= 32 RR

LevofloxacinLevofloxacin <= 1<= 1 SS

CefotetanCefotetan 3232 II

CefepimeCefepime <= 4<= 4 SS

Piperacillin/tazobactamPiperacillin/tazobactam 3232 II

Question #12Question #12

Is the Is the PantoeaPantoea strain described above susceptible to strain described above susceptible to cefotetan?cefotetan?

A. YesA. Yes

B. NoB. No

44%44%

52%52%

Bacteriology Final Reports – Bacteriology Final Reports – E. cloacaeE. cloacae

AntibioticAntibiotic First CultureFirst Culture Second CultureSecond Culture

AmpicillinAmpicillin >= 32, R>= 32, R >= 32, R>= 32, R

CefazolinCefazolin >= 32, R>= 32, R >= 32, R>= 32, R

CeftazidimeCeftazidime <=8, S<=8, S >= 32, R>= 32, R

Trimethoprim-sulfaTrimethoprim-sulfa <=10, S<=10, S <=10, S<=10, S

MeropenemMeropenem <= 2, S<= 2, S <= 2, S<= 2, S

GentamicinGentamicin <= 0.5, S<= 0.5, S <= 0.5, S<= 0.5, S

Ampicillin/sulbactamAmpicillin/sulbactam >= 32, R>= 32, R >= 32, R>= 32, R

LevofloxacinLevofloxacin <= 1, S<= 1, S <= 1, S<= 1, S

CefotetanCefotetan >= 64, R>= 64, R >= 64, R>= 64, R

CefepimeCefepime <= 4, S<= 4, S <= 4, S<= 4, S

Piperacillin/tazobactamPiperacillin/tazobactam 32, I32, I >= 128, R>= 128, R

Question #13Question #13

The above culture was taken one week after the culture The above culture was taken one week after the culture shown earlier. Is it likely that the shown earlier. Is it likely that the Enterobacter Enterobacter isolates isolates represent the same strain from two different cultures?represent the same strain from two different cultures?

A. Yes, because both are susceptible to cefepime.A. Yes, because both are susceptible to cefepime.

B. No, because their susceptibilities to piperacillin-tazobactam B. No, because their susceptibilities to piperacillin-tazobactam and ceftazidime differ.and ceftazidime differ.

C. They could be the same or different. You cannot tell without C. They could be the same or different. You cannot tell without performing more detailed genetic studies.performing more detailed genetic studies.

16%16%

9%9%

70%70%

Question #14Question #14

What is the breakpoint for cefotetan resistance for the What is the breakpoint for cefotetan resistance for the Enterobacter cloacaeEnterobacter cloacae??

A. 32A. 32

B. 64B. 64

C. 128C. 128

Breakpoint for CefotetanBreakpoint for Cefotetan

Enterobacter cloacaeEnterobacter cloacae PantoeaePantoeae

SuscSusc IntpIntp SuscSusc IntpIntp

CefotetanCefotetan >= 64>= 64 RR 3232 II

Question #14Question #14

What is the breakpoint for cefotetan resistance for the What is the breakpoint for cefotetan resistance for the Enterobacter cloacaeEnterobacter cloacae??

A. 32A. 32

B. 64B. 64

C. 128C. 128

61%61%

18%18%

13%13%

Distribution of Scores on Bacteriology

Report Interpretation Test for Internists

Faculty (n=42) M=10.5; StdErr=0.38

Resident(n=48) M=10.4; StdErr=0.26

RCORRECT

14.00

13.00

12.00

11.00

10.00

9.00

8.00

7.00

6.00

5.00

1.00

Count

16

14

12

10

8

6

4

20

Faculty

Resident

Random CommentsRandom Comments

• I know I need to review this – how I know I need to review this – how embarrassing!embarrassing!

• Note to Dr. Rice: You’re right! We do Note to Dr. Rice: You’re right! We do learn too much cardiology and not enough learn too much cardiology and not enough ID in our programID in our program

ConclusionsConclusions

• Clinicians are more adept at interpreting Clinicians are more adept at interpreting Microbiology laboratory reports than we give Microbiology laboratory reports than we give them credit forthem credit for

• The subtleties of antimicrobial testing are The subtleties of antimicrobial testing are understood by most medical staff under the understood by most medical staff under the conditions of this testconditions of this test

• However, this understanding is not complete, However, this understanding is not complete, and will benefit from expert Infectious Diseases and will benefit from expert Infectious Diseases input in complicated casesinput in complicated cases