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

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
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
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
Disclaimers
• This is not a scientifically validated study
• This is not a random sample of Medical
Staff
Acknowledgement
• This survey was developed, administered
and analyzed with the indispensable and
highly professional assistance of Klara
Papp, Ph.D.
Question #1
A Minimal Inhibitory Concentration (MIC) is defined as:
9%
A. The minimal concentration of an antibiotic required to kill the
test organism
90%
B. The minimal concentration of an antibiotic required to prevent
growth of a standard inoculum of test organisms
1%
C. The minimal concentration of an antibiotic achievable in
human serum
D. The minimal concentration of an antibiotic achievable in
human urine
Question #2
What is a breakpoint?
25%
A. The concentration of an antibiotic required to inhibit growth of
an organism in vitro
5%
B. The concentration of an antibiotic that becomes toxic to
human tissues
68%
C. The MIC determined to represent a high likelihood for
successful treatment of a bacterial strain with a specific
antibiotic
Question #3
Who defines the breakpoints for different antibiotics?
37%
A. The American Society for Microbiology
16%
B. The Food and Drug Administration
45%
C. The National Committee for Clinical Laboratory Standards
1%
D. The American College of Physicians
Question #4
Important considerations in determining breakpoints for specific
antibiotics include:
14%
A. Achievable serum concentrations of the antibiotic
B. The pharmacokinetics of the antibiotic
1%
84%
C. The pharmacodynamics of antibiotic-organism interactions in
animal studies
D. All of the above
Question #5
Is the Klebsiella oxytoca susceptible to meropenem?
A. Yes
B. No
Bacteriology Final Report – K. oxytoca
Antibiotic
Susceptibility
Interpretation
Amikacin
<= 2
S
Ampicillin
>= 32
R
Cefazolin
>= 32
R
Ceftazidime
>=32
R
Trimethoprim-sulfa
>=320
R
Meropenem
<= 2
S
Gentamicin
>= 16
R
Ampicillin/sulbactam
>= 32
R
Levofloxacin
4
I
Cefotetan
I
I
Cefepime
<= 4
S
64
I
Piperacillin/tazobactam
Question #5
Is the Klebsiella oxytoca susceptible to meropenem?
95%
3%
A. Yes
B. No
Question #7
What is the breakpoint for Pseudomonas aeruginosa resistance
to ceftazidime?
A. >=8
B. >=32
C. Insufficient information
Bacteriology Final Report – P. aeruginosa
Antibiotic
Susceptibility
Interpretation
Amikacin
S
S
Ceftazidime
S
S
Trimethoprim-sulfa
R
R
Meropenem
R
R
Gentamicin
R
R
R
R
Cefepime
S
S
Piperacillin/tazobactam
S
S
Ampicillin
Cefazolin
Ampicillin/sulbactam
Levofloxacin
Cefotetan
Question #7
What is the breakpoint for Pseudomonas aeruginosa resistance
to ceftazidime?
14%
A. >=8
7%
B. >=32
77%
C. Insufficient information
Question #8
Under what circumstances would the results of the
enterococcal synergy testing shown in this report be
useful?
8%
A. For the treatment of urinary tract infection
20%
B. For the treatment of infections in which Gram negative bacilli are
also involved
64%
C. For the treatment of endocarditis
6%
D. Synergy testing is never useful
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?
22%
A. Yes
74%
B. No
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”
Question #10
In what type of infection could you use levofloxacin with
greatest confidence against this strain of K. oxytoca?
2%
A. Abdominal abscess
9%
B. Aspiration pneumonia
75%
C. Urinary tract infection
7%
D. Osteomyelitis
Answers to Why
• Most commented appropriately on
achievable urine levels
Question #12
Is the Pantoea strain described above susceptible to
cefotetan?
A. Yes
B. No
Bacteriology Final Report - Pantoea
Antibiotic
Susceptibility
Interpretation
Ampicillin
>= 32
R
Cefazolin
>= 32
R
Ceftazidime
>=32
R
Trimethoprim-sulfa
<=10
S
Meropenem
<= 2
S
Gentamicin
<= 0.05
S
Ampicillin/sulbactam
>= 32
R
Levofloxacin
<= 1
S
Cefotetan
32
I
Cefepime
<= 4
S
32
I
Piperacillin/tazobactam
Question #12
Is the Pantoea strain described above susceptible to
cefotetan?
44%
A. Yes
52%
B. No
Bacteriology Final Reports – E. cloacae
Antibiotic
First Culture
Second Culture
Ampicillin
>= 32, R
>= 32, R
Cefazolin
>= 32, R
>= 32, R
Ceftazidime
<=8, S
>= 32, R
Trimethoprim-sulfa
<=10, S
<=10, S
Meropenem
<= 2, S
<= 2, S
Gentamicin
<= 0.5, S
<= 0.5, S
Ampicillin/sulbactam
>= 32, R
>= 32, R
<= 1, S
<= 1, S
Cefotetan
>= 64, R
>= 64, R
Cefepime
<= 4, S
<= 4, S
32, I
>= 128, R
Levofloxacin
Piperacillin/tazobactam
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?
9%
A. Yes, because both are susceptible to cefepime.
16%
B. No, because their susceptibilities to piperacillin-tazobactam
and ceftazidime differ.
70%
C. They could be the same or different. You cannot tell without
performing more detailed genetic studies.
Question #14
What is the breakpoint for cefotetan resistance for the
Enterobacter cloacae?
A. 32
B. 64
C. 128
Breakpoint for Cefotetan
Enterobacter cloacae
Cefotetan
Pantoeae
Susc
Intp
Susc
Intp
>= 64
R
32
I
Question #14
What is the breakpoint for cefotetan resistance for the
Enterobacter cloacae?
18%
A. 32
61%
B. 64
13%
C. 128
Distribution of Scores on Bacteriology
Report Interpretation Test for Internists
16
14
12
10
8
6
4
Faculty
2
0
Resident
1.00
6.00
5.00
8.00
7.00
10.00
9.00
RCORRECT
Faculty (n=42) M=10.5; StdErr=0.38
Resident(n=48) M=10.4; StdErr=0.26
12.00
11.00
14.00
13.00
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
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