Antibiograms
CLSI M39-A4 2014
Antibiograms: CLSI M39-A4; 2014
Introduction • This guideline presents specific recommendations for the collection,
analysis, and presentation of cumulative antimicrobial susceptibility test data.
• Among the issues addressed are: – the way in which multiple isolates from the same patient should be handled – the species included or combined in a statistic – the frequency of data analysis, and – the format for data presentation.
• This guideline also identifies additional data analysis and presentation
options that may be useful to certain clinicians for specialized applications.
• It is important to recognize that the specific recommendations presented in the M39 have been made with the primary aim of guiding clinicians in the selection of initial empirical antimicrobial therapy for infections.
M39 has been reorganized into two parts-
• Part I describes the routine cumulative antibiogram
• Part II describes what is referred to as the “enhanced antibiogram.” – Includes suggestions for analyzing and presenting
cumulative antibiogram data to answer specific questions about susceptibility patterns in a particular facility.
– These reports may not be needed on a routine basis.
Antibiograms: CLSI M39-A4; 2014
The following recommendations are made for preparing an antibiogram:
• Analyze and present a cumulative antibiogram report at least
annually.
• Include only final, verified test results.
• Include only species with testing data for 30 isolates.
• Include only diagnostic (not surveillance) isolates.
• Eliminate duplicates by including only the first isolate of a species/patient/analysis period, irrespective of body site or antimicrobial susceptibility profile.
Antibiograms: CLSI M39-A4; 2014
The following recommendations are made for preparing an antibiogram (con’t):
• Calculate %S; include antimicrobial agents routinely tested including those that might be suppressed using selective reporting rules; do not report supplemental agents selectively tested only on resistant isolates.
• Report the %S and do not include the %I in the statistics.
• Streptococcus pneumoniae and cefotaxime/ceftriaxone/penicillin: list the %S using
both meningitis and nonmeningitis breakpoints.
• Viridans group streptococci and penicillin: list both the %I and the %S – Treatment for Viridan strep infective endocarditis varies based on penicillin MIC; even isolates
that are “I” can still be candidates for penicillin therapy.
• Stahylococcus aureus: list the %S for all isolates and the MRSA subset.
Antibiograms: CLSI M39-A4; 2014
Data
• Organism (>29)
• specimen type (urine, blood, other…)
• patient location (IP and OP)
• susceptibility test method (DD or MIC or combine)
• The use of consistent, unambiguous codes or values for reporting is important. – The use of manually entered “free-text” is discouraged.
Antibiograms: CLSI M39-A4; 2014
Patient Information Required:
• A unique patient identification number
• Health care facility (for laboratories serving multiple facilities)
Patient Information Desirable:
• Date of birth or age
• Sex
• Patient location at the time the specimen was obtained: inpatient ward, nursing unit, clinic, nursing home, etc.
• Clinical service, if applicable (eg, medicine, surgery, obstetrics)
• Admission date
Antibiograms: CLSI M39-A4; 2014
Specimen Information Required
• Specimen type (eg, blood, CSF, urine, sputum, wound, etc.)
• Identifying specimens submitted for purposes other than diagnosing infection in patients (eg, infection control, quality control, proficiency testing, screening, surveillance)
• Date of specimen collection
• Specimen number (unique)
Specimen Information Desired
• Body site from which specimen was obtained (eg, right leg, LLL etc.)
Antibiograms: CLSI M39-A4; 2014
Organism Information Required • Identification (preferably genus and species; genus or organism group [eg,
Enterococcus spp., viridans group streptococci] when species is not available)
Organism Information Desired • An isolate number • A mechanism to permit the comparison of organism results over time,
regardless of taxonomic name changes (eg, Pseudomonas maltophilia, Xanthomonas maltophilia, and Stenotrophomonas maltophilia)
• Supplemental information from infection control or clinical services: – Colonization or infection – Community acquired or health care associated
Antibiograms: CLSI M39-A4; 2014
AST Information Required • “VERIFIED” MIC or DD zone diameters and/or final test
interpretations
• Results of all antimicrobial agents tested, including those that are not routinely reported (e.g., cascade/selective reporting).
• Specialized test results if they represent a primary testing method used to determine susceptibility or resistance (eg, -lactamase test, agar screening test, mecA detection).
AST Information Desired
Antibiograms: CLSI M39-A4; 2014
AST Information Desired • Individual data fields for the MIC or DD values and the
final interpretation reported in the patient medical record. – These are needed for the analysis of historical data in the event
that breakpoints change over time.
• Specific susceptibility test system used: – broth microdilution
– agar dilution
– commercial system
– specific MIC panel
Antibiograms: CLSI M39-A4; 2014
Facility • Cumulative antimicrobial susceptibility test reports should be
based on local facility-specific susceptibility data. • Separate reports should be generated for each health care
facility provided sufficient numbers of isolates have been tested – Where isolate numbers are too low, it may be possible to aggregate
data from multiple smaller facilities, if they have a similar clinical case mix and serve a similar population in the same geographical area.
Frequency • For the purpose of providing reasonably current data to guide
empirical antimicrobial therapy choices, it is recommended that data be analyzed at least annually. – More frequent analysis may be performed when large numbers of
isolates are tested, when new antimicrobial agents are tested, or when other clinically important changes occur or are perceived.
Antibiograms: CLSI M39-A4; 2014
Isolates • Only the first isolate of a given species per patient, per
analysis period (eg, one year) should be included, irrespective of body site or antimicrobial susceptibility profile. – Multiple isolates of the same species are frequently
recovered from successive cultures from the same patient. These isolates may or may not represent identical strains.
• Inclusion of multiple isolates from an individual patient significantly bias estimates in favor of the isolates recovered from patients who are cultured most frequently.
– If not excluded the risk of acquiring a resistant strain for a typical patient may thus be significantly overstated.
Antibiograms: CLSI M39-A4; 2014
Isolates
• Include isolates from human patient specimens collected for diagnostic purposes only.
– Do not include data on isolates recovered from:
• surveillance cultures:
– VRE
– MRSA
• environmental cultures
• other non-patient sources
• In some cases, when small numbers of a species are tested per year, a facility may wish to analyze data for several years combined (eg, 2005 to 2010) [footnote].
Antibiograms: CLSI M39-A4; 2014
Antimicrobial agents • Include only antimicrobial agents routinely
tested – Not those tested by special request on R-isolates
• Will skew the results towards resistance
• Surrogate antimicrobial agents: – Report the agent represented by the surrogate.
• E.g., when using the cefoxitin test as a surrogate for detection of oxacillin-resistant staphylococci, report %S for oxacillin, do not report %S for cefoxitin
• E.g., when using the oxacillin DD screen as a surrogate for detection of penicillin-susceptible S. pneumoniae, report %S for penicillin, do not report %S for oxacillin
Antibiograms: CLSI M39-A4; 2014
• Calculations – Include only the percentage of isolates that test “S” to the
listed antimicrobial agent. – The percentage of isolates that have an “I” interpretation
should not be included in the %S statistic. – Exception:
• For viridans group Streptococcus spp. and penicillin, calculate both the %S and the %I and list both on the antibiogram report
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– E.g., D-zone: • Clindamycin is correctly reported as resistant for isolates of
staphylococci, pneumococci, or β-hemolytic streptococci that test erythromycin resistant and clindamycin susceptible but are shown to have inducible clindamycin resistance (D-zone +).
• Use the corrected interpretation when calculating the %S.
Antibiograms: CLSI M39-A4; 2014
How to handle changes in Interpretive Breakpoints
“Your 2013 Antibiogram”
*Revised (2010) CLSI Enterobacteriaceae interpretive criteria (µg/mL) for susceptible are being used for the first time to calculate %S; these are ≤ 1 µg/mL for ceftriaxone and ≤ 1 µg/mL for meropenem. Previous CLSI interpretive criteria for susceptible were ≤ 8 µg/mL for ceftriaxone and ≤ 4 µg/mL for meropenem.
Antibiograms: CLSI M39-A4; 2014
Organism
No.
Strains
%S
AMK AMP CFZ CRO* CIP GEN MEM* PTZ SXT TOB
E. coli 1165 100 62 88 94 88 100 100 88 74 100
Enterobacter
cloacae 223 100 – – 82 91 91 99 82 72 100
Klebsiella
pneumoniae 521 100 – – 78 94 93 93 86 75 100
How to validation your antibiogram - • Include only species for which there are 30 or more isolates.
– If data are listed for organisms with fewer than 30 isolates available, determine if it is essential to include the species; if yes, append a note to indicate less statistical validity of the %S.
– Alternatively, consider analyzing data from a longer time frame (eg, two years) and footnote this exception on the cumulative antibiogram report.
• Be sure to define all your abbreviations. • Only include %S data for antimicrobial agents that are appropriate
for the species. – For antimicrobial agents which only “susceptible” interpretive criteria
are provided, any %S calculation that is not 100% should be investigated.
– This should be done at the time the observation is made and before reporting results on the individual patient report.
Antibiograms: CLSI M39-A4; 2014
Specifics
Antibiograms: CLSI M39-A4; 2014
Specifics: S. pneumoniae • Penicillin
– For all isolates tested, regardless of body site, calculate and list the %S using meningitis, nonmeningitis, and penicillin V (oral penicillin) breakpoints
– NOTE: It may not be necessary to include data for penicillin V if that information is not used in the facility.
• Cefotaxime and ceftriaxone – For all isolates tested, regardless of body site, calculate and
list the %S using both meningitis and nonmeningitis breakpoints.
Antibiograms: CLSI M39-A4; 2014
Specifics: S. pneumoniae
* Breakpoints differ for cefotaxime, ceftriaxone, and penicillin based on diagnosis. Cefotaxime, ceftriaxone, and penicillin meningitis applies to susceptibility for patients who have meningitis; cefotaxime, ceftriaxone, and penicillin nonmeningitis applies to susceptibility for patients who do not have meningitis.
Antibiograms: CLSI M39-A4; 2014
Organism
No.
Strains
%S
AMX CTX CRO CLI ERY LVX
PEN
(IV)
PEN
(oral) SXT VAN
S. pneumoniae 110 94 –* –* 81 64 99 –* 64 69 100
Meningitis 110 – 85 84 – – – 64 – – –
Nonmeningitis 110 – 95 96 – – – 84 – – –
Specifics: S. pneumoniae
*Breakpoints differ for cefotaxime, ceftriaxone, and penicillin based on diagnosis. M (meningitis) applies to susceptibility for patients who have meningitis; NM (nonmeningitis) applies to susceptibility for patients who do not have meningitis.
Antibiograms: CLSI M39-A4; 2014
Organism #
%S
AMX CTX CRO CLI ERY LVX
PEN
(IV)
PEN
(oral) SXT VAN
S.
pneumoniae 90 94
85M/95NM
*
84M/96NM
* 81 64 99
64M/84NM
* 64 69 100
Specifics: Viridans Group Streptococcus spp.
• For penicillin: in addition to the %S to penicillin, calculate and list separately the %S and %I to penicillin.
• The %I can be indicated in a footnote. – E.g., if 80% are susceptible to penicillin, the footnote
might then read: • “For the 20% nonsusceptible isolates, 15% were intermediate
and 5% were resistant to penicillin.”
– Only include data from sterile body sites for VS group
Antibiograms: CLSI M39-A4; 2014
Specifics: Susceptible Dose-Dependent • For antimicrobial agents that have susceptible dose-
dependent (SDD) interpretive criteria (eg, cefepime and Enterobacteriaceae), in addition to the %S to cefepime, calculate and list separately the %S and percent SDD (%SDD) to cefepime for each organism (2014 antibiogram).
• The %SDD can be indicated in a footnote. – E.g., with E. cloacae, if 89% of isolates are susceptible, the
footnote might then read: • “In addition to the 89% susceptible results, 8% of the isolates were
susceptible-dose dependent (MIC 4 to 8 µg/mL) and 3% were resistant to cefepime.”
Antibiograms: CLSI M39-A4; 2014
Specifics: MRSA
Antibiograms: CLSI M39-A4; 2014
Organism No.
%S
CLI DOX ERY GEN OXA PEN RIF SXT VAN
S. aureus
1317 80 98 50 93 68 13 98 96 100
Oxacillin-
resistant
S.aureus
(MRSA)
421 44 96 4 79 0 0 95 94 100
Oxacillin-
susceptible
S.aureus
(MSSA)
896 97 99 72 99 100 18 99 97 100
It may be useful to perform a separate analysis for oxacillin-resistant S. aureus (MRSA) and oxacillin-susceptible S. aureus (MSSA) to demonstrate that many MRSA have lower %S to some other antistaphylococcal agents.
Specifics: MRSA
Antibiograms: CLSI M39-A4; 2014
Organism No.
%S
CLI DOX ERY GEN OXA PEN RIF SXT VAN
S. aureus
1317 80 98 50 93 68 13 98 96 100
Oxacillin-
resistant
S.aureus
(MRSA)
421 44 96 4 79 0 0 95 94 100
Oxacillin-
susceptible
S.aureus
(MSSA)
896 97 99 72 99 100 18 99 97 100
It may be useful to perform a separate analysis for oxacillin-resistant S. aureus (MRSA) and oxacillin-susceptible S. aureus (MSSA) to demonstrate that many MRSA have lower %S to some other antistaphylococcal agents.
Specifics: Enterococcus • Due to differences in susceptibility profiles for
Enterococcus faecalis and Enterococcus faecium: – Perform a separate analysis for E. faecalis and E.
faecium
– Then perform an analysis for all enterococci as a group
• This can be especially useful when laboratories only identify select enterococcal isolates to the species level
– sterile body site isolates speciate
– VRE speciate
Antibiograms: CLSI M39-A4; 2014
Specifics: Enterococcus
Antibiograms: CLSI M39-A4; 2014
Organism
No.
Strains
%S
AMP DOX PEN QDA VAN
GEN
Syn
STR
Syn
E. faecalis + 77 100 84 100 1 95 60 71
E. faecium + 261 2 89 2 99 13 40 14
All Enterococcus spp.* 1525 ^ 74 69 74 32 83 71 60
+ Species identification performed only from sterile sources and isolates of VRE. * Profile from all enterococcus isolates (E.faecalis, E.faecium, and all others). ^ A majority of the 1525 isolates are from urine and are likely comprised of the most common Enterococcus species (E. faecalis and E. faecium).
Gram-Negative Organisms
No.
Strains
Am
ikacin
Am
picillin
Cefa
zolin
Cefo
taxim
e
Cefta
zidim
e
Cip
roflo
xacin
Nitro
fura
nto
in†
Gen
tam
icin
Mero
pen
em
Pip
eracillin
-ta
zob
acta
m
Trim
ethop
rim-
sulfa
meth
oxazo
le
Tob
ram
ycin
Acinetobacter baumannii 32 80 R R 34 52 51 –‡ 60 80 46 58 59
Citrobacter freundii 49 100 R R 72 67 90 78 100 99 67 67 100
Enterobacter aerogenes 31 100 R R 68 69 92 85 91 99 74 95 91
Enterobacter cloacae 76 99 R R 61 62 92 81 90 99 77 84 90
Escherichia coli 1433 99 36 68 96 94 72 98 91 99 51 65 92
Klebsiella pneumoniae 543 99 R 72 91 92 84 74 94 95 86 81 94
Morganella morganii 44 100 R R 85 81 99 R 100 99 64 75 100
Proteus mirabilis 88 100 87 80 99 99 89 R 90 100 70 73 93
Pseudomonas aeruginosa 397 97 R R R 76 75 R 80 80 85 R 83
Salmonella spp. 32 – 88 – 97 97 90 – – 100 91 86 –
Serratia marcescens 50 100 R R 82 94 95 R 94 99 94 91 89
Shigella spp. 33 – 64 – 100 100 95 – – 100 84 69 –
Stenotrophomonas maltophilia 72 R R R R 63 6 R R R – 98 R
Antibiograms: Data Presentation
Antibiograms: Data Presentation
Gram-Negative Organisms
No.
Strains
β-lactams Aminoglycosides FQs Other
Am
picillin
Cefa
zolin
Cefo
taxim
e
Cefta
zidim
e
Mero
pen
em
Pip
eracillin
-ta
zob
acta
m
Am
ikacin
Gen
tam
icin
Tob
ram
ycin
Cip
roflo
xacin
Nitro
fura
nto
in†
Trim
ethop
rim-
sulfa
meth
oxazo
le
Acinetobacter baumannii 32 R R 34 52 80 46 80 60 59 51 –‡ 58
Citrobacter freundii 49 R R 72 67 99 67 100 100 100 90 78 67
Enterobacter aerogenes 31 R R 68 69 99 74 100 91 91 92 85 95
Enterobacter cloacae 76 R R 61 62 99 77 99 90 90 92 81 84
Escherichia coli 1433 36 68 96 94 99 51 99 91 92 72 98 65
Klebsiella pneumoniae 543 R 72 91 92 99 86 99 94 94 84 74 81
Morganella morganii 44 R R 85 81 99 64 100 100 100 99 R 75
Proteus mirabilis 88 87 80 99 99 100 70 100 90 93 89 R 73
Pseudomonas aeruginosa 397 R R R 76 80 85 97 80 83 75 R R
Salmonella spp. 32 88 – 97 97 100 91 – – – 90 – 86
Serratia marcescens 50 R R 82 94 99 94 100 94 89 95 R 91
Shigella spp. 33 64 – 100 100 100 84 – – – 95 – 69
Stenotrophomonas maltophilia 72 R R R 63 R R R R R 6 R 98
Antibiograms: Data Presentation
Gram-Negative Organisms
No.
Strains
β-lactams Aminoglycosides FQs Other
Am
picillin
Cefa
zolin
Cefo
taxim
e
Cefta
zidim
e
Mero
pen
em
Pip
eracillin
-ta
zob
acta
m
Am
ikacin
Gen
tam
icin
Tob
ram
ycin
Cip
roflo
xacin
Nitro
fura
nto
in†
Trim
ethop
rim-
sulfa
meth
oxazo
le
Acinetobacter baumannii 32 R R 34 52 80 46 80 60 59 51 –‡ 58
Citrobacter freundii 49 R R 72 67 99 67 100 100 100 90 78 67
Enterobacter aerogenes 31 R R 68 69 99 74 100 91 91 92 85 95
Enterobacter cloacae 76 R R 61 62 99 77 99 90 90 92 81 84
Escherichia coli 1433 36 68 96 94 99 51 99 91 92 72 98 65
Klebsiella pneumoniae 543 R 72 91 92 99 86 99 94 94 84 74 81
Morganella morganii 44 R R 85 81 99 64 100 100 100 99 R 75
Proteus mirabilis 88 87 80 99 99 100 70 100 90 93 89 R 73
Pseudomonas aeruginosa 397 R R R 76 80 85 97 80 83 75 R R
Salmonella spp. 32 88 – 97 97 100 91 – – – 90 – 86
Serratia marcescens 50 R R 82 94 99 94 100 94 89 95 R 91
Shigella spp. 33 64 – 100 100 100 84 – – – 95 – 69
Stenotrophomonas maltophilia 72 R R R 63 R R R R R 6 R 98
Antibiograms: Data Presentation
Gram-Negative Organisms
No.
Strains
β-lactams Aminoglycosides FQs Other
Am
picillin
Cefa
zolin
Cefo
taxim
e
Cefta
zidim
e
Mero
pen
em
Pip
eracillin
-ta
zob
acta
m
Am
ikacin
Gen
tam
icin
Tob
ram
ycin
Cip
roflo
xacin
Nitro
fura
nto
in†
Trim
ethop
rim-
sulfa
meth
oxazo
le
Citrobacter freundii 49 R R 72 67 99 67 100 100 100 90 78 67
Enterobacter aerogenes 31 R R 68 69 99 74 100 91 91 92 85 95
Enterobacter cloacae 76 R R 61 62 99 77 99 90 90 92 81 84
Escherichia coli 1433 36 68 96 94 99 51 99 91 92 72 98 65
Klebsiella pneumoniae 543 R 72 91 92 99 86 99 94 94 84 74 81
Morganella morganii 44 R R 85 81 99 64 100 100 100 99 R 75
Proteus mirabilis 88 87 80 99 99 100 70 100 90 93 89 R 73
Salmonella spp. 32 88 – 97 97 100 91 – – – 90 – 86
Serratia marcescens 50 R R 82 94 99 94 100 94 89 95 R 91
Shigella spp. 33 64 – 100 100 100 84 – – – 95 – 69
Acinetobacter baumannii 32 R R 34 52 80 46 80 60 59 51 –‡ 58
Pseudomonas aeruginosa 397 R R R 76 80 85 97 80 83 75 R R
Stenotrophomonas maltophilia 72 R R R 63 R R R R R 6 R 98
Memorial Medical Center January - December 2013 Antibiogram
(Percent Susceptible)
Gram-Negative Organisms
# of
Strains
Am
ikacin
Am
picillin
Cefa
zolin
Cefo
taxim
e
Cefta
zidim
e
Cip
roflo
xacin
Nitro
fura
nto
in†
Gen
tam
icin
Mero
pen
em
Pip
eracillin
-ta
zob
acta
m
Trim
ethop
rim-
sulfa
meth
oxazo
le
Tob
ram
ycin
Acinetobacter baumannii 32 80 R R 34 52 51 –‡ 60 80 46 58 59
Citrobacter freundii 49 100 R R 72 67 90 78 100 99 67 67 100
Enterobacter aerogenes 31 100 R R 68 69 92 85 91 99 74 95 91
Enterobacter cloacae 76 99 R R 61 62 92 81 90 99 77 84 90
Escherichia coli 1433 99 36 68 96 94 72 98 91 99 51 65 92
Klebsiella pneumoniae 543 99 R 72 91 92 84 74 94 95 86 81 94
Morganella morganii 44 100 R R 85 81 99 R 100 99 64 75 100
Proteus mirabilis 88 100 87 80 99 99 89 R 90 100 70 73 93
Pseudomonas aeruginosa 397 97 R R R 76 75 R 80 80 85 R 83
Salmonella spp. 32 – 88 – 97 97 90 – – 100 91 86 –
Serratia marcescens 50 100 R R 82 94 95 R 94 99 94 91 89
Shigella spp. 33 – 64 – 100 100 95 – – 100 84 69 –
Stenotrophomonas maltophilia 72 R R R R 63 6 R R R – 98 R
• Acinetobacter baumannii
• Citrobacter freundii
• Enterobacter aerogenes
• Enterobacter cloacae
• Escherichia coli
• Haemophilus influenzae [e.g., percent -lactamase positive]
• Klebsiella oxytoca
• Klebsiella pneumoniae
• Morganella morganii
• Proteus mirabilis
• Providencia spp.**
• Pseudomonas aeruginosa
• Salmonella spp.**
• Serratia marcescens
• Shigella spp.**
• Stenotrophomonas maltophilia
Antibiograms: GN
List organisms alphabetically, by organism group, or by prevalence. **Analyze by organism group or genus if species information is not routinely
available.
• Enterococcus spp. – Separate into E. faecalis and E. faecium when identified to species
level if sufficient numbers of isolates are tested.
• S. aureus (MRSA and MSSA)
• Coagulase-negative staphylococci spp. – Consider excluding Staphylococcus lugdunensis and Staphylococcus
saprophyticus, which could be listed separately if sufficient numbers of isolates are tested.
• Streptococcus pneumoniae
• Viridans group streptococci spp. – Include those only from sterile body sites and if sufficient numbers
of isolates are tested (include footnote about %I).
Antibiograms: GP
• Report only bacteria for which 30 or more isolates of a given species are available. – This is based on a desire to include a reasonable number of
isolates upon which to calculate the %S, while allowing the reporting of clinically relevant organisms that are isolated in small numbers .
– If data are included for organisms with fewer than 30 isolates, a note should be appended to indicate less statistical validity of the estimates of %S.
– When there are fewer than 30 isolates, it may be appropriate to group several species within a genus together (eg, Shigella spp.).
• Include the number of observations (N) for each organism – interpret the relative frequency of each organism as a cause of
infection at their institution – estimate the relative precision of the %S value
Antibiograms: Number of Organisms
• Enter the %S for each organism/antimicrobial
agent in the respective box.
• Place a dash (–) in the data box if an antimicrobial agent is not tested, or is known to be clinically ineffective (e.g., the Salmonella spp. and narrow-spectrum cephalosporins).
• Place an “R” in the data box when it is known that the species or organism group is intrinsically resistant to the antimicrobial agent.
Antibiograms: Data
Antimicrobial Agent
Organism
A
mp
icil
lin
Am
ox
icil
lin
-cla
vu
lan
ate
Am
pic
illi
n-
su
lba
cta
m
Pip
era
cil
lin
Tic
arc
illi
n
Ce
ph
alo
sp
ori
n I
:
Ce
fazo
lin
, C
ep
ha
loth
in
Ce
ph
am
yc
ins
:
Cefo
xit
in, C
efo
teta
n
Cep
ha
los
po
rin
II:
Cefu
roxim
e
Imip
en
em
Te
tra
cyc
lin
es
/
Tig
ec
yc
lin
e
Nit
rofu
ran
toin
Po
lym
yx
in B
Co
lis
tin
Am
ino
gly
co
sid
es
Citrobacter freundii R R R R R R
Citrobacter koseri R R R
Enterobacter aerogenes R R R R R R
Enterobacter cloacae R R R R R R
Escherichia coli
There is no intrinsic resistance to β-lactams in this
organism.
Escherichia hermannii R R
Hafnia alvei R R R R R
Klebsiella pneumoniae R R
Morganella morganii R R R R * R R R
Proteus mirabilis
There is no intrinsic resistance to penicillins and
cephalosporins in this organism.
* R R R
Proteus penneri R R R * R R R
Proteus vulgaris R R R * R R R
Providencia rettgeri R R R * R R R
Providencia stuartii R R R R R R †
Salmonella and Shigella spp.
There is no intrinsic resistance to β-lactams in these
organisms; see Table 2A, comment (6) for reporting.
Serratia marcescens R R R R R R R R
Yersinia enterocolitica R R R R
M100 Appendix B - Intrinsic Resistance Tables (B1-B4)
Gram-Negative Organisms
No.
Strains
Am
ikacin
Am
picillin
Cefa
zolin
Cefo
taxim
e
Cefta
zidim
e
Cip
roflo
xacin
Nitro
fura
nto
in†
Gen
tam
icin
Mero
pen
em
Pip
eracillin
-ta
zob
acta
m
Trim
ethop
rim-
sulfa
meth
oxazo
le
Tob
ram
ycin
Acinetobacter baumannii 32 80 R R 34 52 51 –‡ 60 80 46 58 59
Citrobacter freundii 49 100 R R 72 67 90 78 100 99 67 67 100
Enterobacter aerogenes 31 100 R R 68 69 92 85 91 99 74 95 91
Enterobacter cloacae 76 99 R R 61 62 92 81 90 99 77 84 90
Escherichia coli 1433 99 36 68 96 94 72 98 91 99 51 65 92
Klebsiella pneumoniae 543 99 R 72 91 92 84 74 94 95 86 81 94
Morganella morganii 44 100 R R 85 81 99 R 100 99 64 75 100
Proteus mirabilis 88 100 87 80 99 99 89 R 90 100 70 73 93
Pseudomonas aeruginosa 397 97 R R R 76 75 R 80 80 85 R 83
Salmonella spp. 32 – 88 – 97 97 90 – – 100 91 86 –
Serratia marcescens 50 100 R R 82 94 95 R 94 99 94 91 89
Shigella spp. 33 – 64 – 100 100 95 – – 100 84 69 –
Stenotrophomonas maltophilia 72 R R R R 63 6 R R R – 98 R
“N”
Gram-Negative Organisms
No.
Strains
Am
ikacin
Am
picillin
Cefa
zolin
Cefo
taxim
e
Cefta
zidim
e
Cip
roflo
xacin
Nitro
fura
nto
in†
Gen
tam
icin
Mero
pen
em
Pip
eracillin
-ta
zob
acta
m
Trim
ethop
rim-
sulfa
meth
oxazo
le
Tob
ram
ycin
Acinetobacter baumannii 32 80 R R 34 52 51 –‡ 60 80 46 58 59
Citrobacter freundii 49 100 R R 72 67 90 78 100 99 67 67 100
Enterobacter aerogenes 31 100 R R 68 69 92 85 91 99 74 95 91
Enterobacter cloacae 76 99 R R 61 62 92 81 90 99 77 84 90
Escherichia coli 1433 99 36 68 96 94 72 98 91 99 51 65 92
Klebsiella pneumoniae 543 99 R 72 91 92 84 74 94 95 86 81 94
Morganella morganii 44 100 R R 85 81 99 R 100 99 64 75 100
Proteus mirabilis 88 100 87 80 99 99 89 R 90 100 70 73 93
Pseudomonas aeruginosa 397 97 R R R 76 75 R 80 80 85 R 83
Salmonella spp. 32 – 88 – 97 97 90 – – 100 91 86 –
Serratia marcescens 50 100 R R 82 94 95 R 94 99 94 91 89
Shigella spp. 33 – 64 – 100 100 95 – – 100 84 69 –
Stenotrophomonas maltophilia 72 R R R R 63 6 R R R – 98 R
%S
Gram-Negative Organisms
No.
Strains
Am
ikacin
Am
picillin
Cefa
zolin
Cefo
taxim
e
Cefta
zidim
e
Cip
roflo
xacin
Nitro
fura
nto
in†
Gen
tam
icin
Mero
pen
em
Pip
eracillin
-ta
zob
acta
m
Trim
ethop
rim-
sulfa
meth
oxazo
le
Tob
ram
ycin
Acinetobacter baumannii 32 80 R R 34 52 51 –‡ 60 80 46 58 59
Citrobacter freundii 49 100 R R 72 67 90 78 100 99 67 67 100
Enterobacter aerogenes 31 100 R R 68 69 92 85 91 99 74 95 91
Enterobacter cloacae 76 99 R R 61 62 92 81 90 99 77 84 90
Escherichia coli 1433 99 36 68 96 94 72 98 91 99 51 65 92
Klebsiella pneumoniae 543 99 R 72 91 92 84 74 94 95 86 81 94
Morganella morganii 44 100 R R 85 81 99 R 100 99 64 75 100
Proteus mirabilis 88 100 87 80 99 99 89 R 90 100 70 73 93
Pseudomonas aeruginosa 397 97 R R R 76 75 R 80 80 85 R 83
Salmonella spp. 32 – 88 – 97 97 90 – – 100 91 86 –
Serratia marcescens 50 100 R R 82 94 95 R 94 99 94 91 89
Shigella spp. 33 – 64 – 100 100 95 – – 100 84 69 –
Stenotrophomonas maltophilia 72 R R R R 63 6 R R R – 98 R
-
Gram-Negative Organisms
No.
Strains
Am
ikacin
Am
picillin
Cefa
zolin
Cefo
taxim
e
Cefta
zidim
e
Cip
roflo
xacin
Nitro
fura
nto
in†
Gen
tam
icin
Mero
pen
em
Pip
eracillin
-ta
zob
acta
m
Trim
ethop
rim-
sulfa
meth
oxazo
le
Tob
ram
ycin
Acinetobacter baumannii 32 80 R R 34 52 51 –‡ 60 80 46 58 59
Citrobacter freundii 49 100 R R 72 67 90 78 100 99 67 67 100
Enterobacter aerogenes 31 100 R R 68 69 92 85 91 99 74 95 91
Enterobacter cloacae 76 99 R R 61 62 92 81 90 99 77 84 90
Escherichia coli 1433 99 36 68 96 94 72 98 91 99 51 65 92
Klebsiella pneumoniae 543 99 R 72 91 92 84 74 94 95 86 81 94
Morganella morganii 44 100 R R 85 81 99 R 100 99 64 75 100
Proteus mirabilis 88 100 87 80 99 99 89 R 90 100 70 73 93
Pseudomonas aeruginosa 397 97 R R R 76 75 R 80 80 85 R 83
Salmonella spp. 32 – 88 – 97 97 90 – – 100 91 86 –
Serratia marcescens 50 100 R R 82 94 95 R 94 99 94 91 89
Shigella spp. 33 – 64 – 100 100 95 – – 100 84 69 –
Stenotrophomonas maltophilia 72 R R R R 63 6 R R R – 98 R
“R”
• Laboratories may use different panels of antimicrobial agents for the testing of isolates from various organism groups or body sites. – E.g., one set of antimicrobial agents may be used for testing urine
gram-negative isolates and another for non urine gram-negative isolates.
• Include the number of observations based on the highest number of organism/antimicrobial agent combinations tested. – If a subset of isolates (eg, urine isolates) is not tested against all
antimicrobial agents, the clinical relevance of the cumulative antimicrobial susceptibility test report data may or may not be affected.
– Sometimes, it might be necessary to report subsets separately.
Antibiograms: Variations in Drug Panels Tested Routinely
Antibiograms: Variations in Drug Panels Tested Routinely
Organism
No.
Strains
%S
AMP CFZ CRO CIP GEN IPM LVX* PTZ SXT
E. coli 3636 61 92 99 92 93 100 80 96 76
Organism
No.
Strains
%S
AMP CFZ CRO CIP GEN IPM LVX* PTZ SXT
E. coli
(All) 3636 61 92 99 92 93 100 80 96 76
E. coli
(Nonurine) 292 44 82 96 80 87 100 80 93 62
E. coli
(Urine) 3417 63 93 99 93 94 100 NT 97 77
*Levofloxacin tested on non-urine isolates only (n = 292). Therefore, results should not be compared to those of other antimicrobial agents listed, all of which were tested against both urine and non-urine isolates.
*Tested on non-urine isolates only (n = 292). Therefore, results should not be compared to those of other antimicrobial agents listed, all of which were tested against both urine and non-urine isolates.
Antibiograms: Change in Drugs Tested Routinely
Organism
No.
Strains
%S
AMP CFZ CPM* CRO CTZ CIP GEN IPM PTZ SXT
E. cloacae 44 R R 86 75 76 93 95 98 84 90
E. coli 378 49 90 96 95 95 77 91 100 86 74
K. pneumoniae 97 R 94 96 94 93 95 100 98 95 86
P. aeruginosa 73 R R 86 R 85 79 91 93 92 R
*Added to test panel August 2012. Results for CPM should not be compared directly to those of other agents as CPM was not tested on all isolates.
Antibiograms: Change in Drugs Tested Routinely
Organism
No.
Strains
%S
AMP CFZ CPM* CRO CTZ CIP GEN IPM PTZ SXT
E. cloacae 44 R R 86 (20) 75 76 93 95 98 84 90
E. coli 378 49 90 96 (155) 95 95 77 91 100 86 74
K. pneumoniae 97 R 94 96 (39) 94 93 95 100 98 95 86
P. aeruginosa 73 R R 86 (27) R 85 79 91 93 92 R
*Added to test panel August 2012. Data for CPM indicates %S (# tested).
Use of the Antibiogram
• The cumulative antibiogram should be used as a guide for empirical antimicrobial therapy until such time that specific AST results for a patient’s organism become available. – Using the antibiogram is one factor the physician employs to choose
empiric therapy.
– Other factors include the organism ID, the antimicrobial agent, patient characteristics, site of infection, etc.
• The antibiogram is increasing in importance as Antibiotic Stewardship Programs evolve in health care facilities. – Individuals responsible for ASPs and those preparing cumulative
antibiograms must work together to ensure these reports are prepared, distributed, and used optimally.
Distribution of the Antibiogram
Pocket Guides • A foldout card with a readable font size (no smaller than 8-point) that fits
in the pocket of a laboratory coat is useful. • A laminated sheet containing the cumulative antibiogram report might
also be placed at the front of each new patient’s chart. • The amount of material presented on the pocket or chart antibiogram
report should be limited, compared to that on a website.
Website Application or Portable Document Format • Presentation of the report on an institution’s website (either in graphical
form or as a downloadable file) may also meet the needs of some clinicians.
• It is important to provide reports in each of the formats most frequently used by prescribing physicians. – E.g., many institutions provide portable devices for use by nurses, medical
students, residents, and house staff who may not wish to carry an additional printed pocket version.
Trifold
Trifold Pocket Antibiogram
Influence of a small “N” • Results of small numbers (< 30) of isolates may be misleading and
usually should not be included in the report. – However, such data should be kept on file in the laboratory for easy access.
• Possible ways to provide guidance for antimicrobial therapy when the number of tested isolates is small include: – Combining data on the organism from data collected over more than 12
consecutive months
– Combining data, when applicable, for more than one species within a genus
– Combining data from several comparable institutions in a geographical area (eg, acute care hospitals)
• Combining data is only appropriate if the %S data among the institutions are similar.
• Providing data from published summaries and guides E.g., Anaerobic antibiogram (just a bit later)
The “Enhanced” Antibiogram
By nursing unit or site of care • Data are segregated by patient location (e.g., ICU, burn
unit, ward, outpatient clinic, nursing home)
• These reports can be used to guide initial empirical antimicrobial therapy for patients at that site of care – ICU patients – Inpatient patients (includes or excludes ICU patients) – Outpatient reports (includes or excludes ED patients)
• Unit- or site of care- specific antibiograms may be useful in
the empirical treatment of patients in those locations – MICU (ventilator-associated pneumonia)
By an organism’s resistance characteristics • Data are segregated by resistance characteristics of a given
organism. – Useful for multidrug-resistant organisms: MRSA, VRE, CRE,
MDR-GNR
By clinical service or patient population • Data are segregated by clinical service, medical or surgical
specialty, or specific patient population. – surgical, pediatric, cystic fibrosis, transplant
By specimen type or infection site • Data are segregated by specimen type or infection site
– urine isolates, blood isolates, other…
The “Enhanced” Antibiogram
Supplemental Analyses of Multidrug-Resistant Organisms
Organism
No.
Strains
%S
AMK AMP CFZ CRO CIP GEN IPM PTZ TET SXT
K. pneumoniae
(All) 1163 63 R 44 48 46 74 64 53 84 46
K. pneumoniae
(Extended-
spectrum
cephalosporin
resistant)
233 30 R 0 0 6 48 100 0 84 3
K. pneumoniae
(Carbapenem-
resistant)
361 5 R 0 0 0 28 0 0 82 0
K. pneumoniae
(Not resistant to
Extended spectrum
cephalosporins or
carbapenems)
569 100 R 84 99 94 96 100 88 87 95
ORGANISM Source
(approx. #
tested)
Amk Aug Amp Cfz Cfp Ctz Ctr Cip Erta Gen Lev Mer Nit P/T Tet Tob T/S
Acinetobacter baumanii Urine (1)
Blood (0)
Other (3)
Citrobacter freundii Urine (4)
Blood (0)
Other (11) 100 18 100 82 82 100 100 100 100 100 100 82 100 100 100
Enterobacter aerogenes Urine (4)
Blood (2)
Other (10) 80 90 100 100 100 100 100 30 90 100 100 100
Enterobacter cloacae Urine (6) 100 83 67 67 83 83 100 83 100 17 67 83 100 67
Blood (2)
Other (24) 100 100 72 68 100 87 96 100 100 26 76 88 96
Escherichia coli Urine (240) 100 83 60 82 98 97 95 89 100 94 89 100 97 95 75 94 83
Blood (14) 100 93 71 93 100 93 93 93 100 100 93 100 100 100 86 100 86
Other (110) 100 89 69 90 100 97 95 92 100 96 92 100 98 95 85 96 89
Klebsiella pneumoniae Urine (57) 100 100 93 100 99 97 97 100 95 97 100 28 97 81 97
Blood (6) 100 83 100 100 100 100 100 100 100 100 17 83 83 100 83
Other (41) 100 100 100 100 100 100 100 100 98 100 25 98 90 100 98
Morganella morganii Urine (2)
Blood (0)
Other (6) 100 100 83 83 100 100 100 100 100 100 83 100 100
Proteus mirabilis Urine (22) 100 100 91 86 100 100 100 87 100 96 86 100 100 96 91
Blood (5) 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100
Other (29) 100 100 72 62 100 100 97 93 100 93 93 100 100 93 83
Serratia marcescens Urine (1)
Blood (0)
Other (11) 100 100 100 91 91 100 100 91 100 100 46 91 100
Pseudomonas aeruginosa Urine (33) 97 88 82 91 79 91 89 97
Blood (7) 100 86 100 100 100 100 100 86 100
Other (55) 100 96 89 93 96 87 95 94 100
Stenotrophomonas maltophilia Urine (2)
Blood (1)
Other (13) 39 69 92
By specimen type or infection site
KP 2013 ANTIBIOGRAM; Inpatient– Sources
January - December
National ANAEROBIC Antibiogram (M100) • Data were generated from unique isolates
from patient specimens submitted to three referral laboratories: – Tufts New England Medical Center, Boston, MA
– Loyola University Medical Center, Maywood, IL
– R.M. Alden Research Laboratory, Culver City, CA
• Testing was performed by standardized agar dilution method.
Calculating Percent Susceptible on Select Groups of Organisms
The Use of Data From External
Surveillance Programs
Anaerobic Organisms
Nu
mb
er
of
Str
ain
s
Am
pic
illi
n-s
ulb
ac
tam
Pip
era
cil
lin
-ta
zo
bac
tam
Cefo
xit
in
Ert
ap
en
em
Imip
en
em
Me
rop
en
em
Cli
nd
am
yc
in
Mo
xif
lox
ac
in
Me
tro
nid
azo
leb
Percent Susceptible
(%S) and Percent
Resistant (%R)c
%S
%R %S %R %S %R %S %R %S %R %S %R %S %R %S %R %S %R
Breakpoints in µg/mL ≤ 8/4 ≥ 32/16 ≤ 32/4 ≥ 128/4 ≤ 16 ≥ 64 ≤ 4 ≥ 16 ≤ 4 ≥ 16 ≤ 4 ≥ 16 ≤ 2 ≥ 8 ≤ 2 ≥ 8 ≤ 8 ≥ 32
B. fragilis 872 89 4 98 1 85 6 96 2 98 2 97 2 64 28 53 38 100 0
B. thetaiotaomicron 342 86 3 92 2 32 13 96 2 99 0 99 1 27 56 44 34 100 0
B. ovatus 67 93 2 93 2 37 15 98 0 100 0 100 0 54 39 43 39 100 0
B. vulgatus 70 67 6 100 0 83 4 98 2 98 2 98 2 49 51 43 46 100 0
B. uniformis 60 87 2 93 0 42 13 97 0 100 0 98 0 35 52 35 50 100 0
B. eggerthii 58 95 0 100 0 98 2 100 0 100 0 100 0 29 55 28 55 100 0
Parabacteroides
distasonis 111 69 11 91 2 41 16 97 0 100 0 99 0 30 41 54 38 100 0
B. fragilis group without B.
fragilis 708 83 4 93 1 40 12 97 1 99 0 99 0 33 42 43 40 100 0
B. fragilis group (all 7
species listed) 1580 86 4 95 2 65 9 97 1 98 1 98 1 50 39 49 39 100 0
Anaerobic
Organisms
Nu
mb
er
of
Str
ain
s
Am
pic
illi
n-
su
lba
cta
m
Pip
era
cil
lin
-
tazo
ba
cta
m
Cefo
xit
in
Ert
ap
en
em
Imip
en
em
Me
rop
en
em
Pe
nic
illi
n/
am
pic
illi
n
Cli
nd
am
yc
in
Mo
xif
lox
ac
in
Me
tro
nid
azo
le
Percent
Susceptible
(%S) and
Percent
Resistant (%R)d
%S
%R %S %R %S %R %S %R %S %R %R %S %
R
%S %R %S %R %S %R
Breakpoints in
µg/mL
≤ 8/4 ≥ 32/16 ≤ 32/4 ≥ 128/4 ≤ 16 ≥ 64 ≤ 4 ≥ 16 ≤ 4 ≥ 16 ≥ 16 ≤ 0.5 ≥ 2 ≤ 2 ≥ 8 ≤ 2 ≥ 8 ≤ 8 ≥ 32
Prevotella spp. 173 98 1 99 1 99 1 100 0 100 0 1 40 49 66 30 59 24 100 0
Fusobacterium
nucleatum-
necrophorum
44 100 0 100 0 100 0 100 0 100 0 0 100 0 10
0
0 95 5 100 0
Anaerobic gram-
positive coccie 168 98 1 100 0 100 0 100 0 100 0 0 96 3 78 20 82 11 98 1
Veillonella spp.b 28 100 0 61 7 100 0 100 0 100 0 0 57 28 89 7 79 14 86 11
P. acnes 34 100 0 100 0 100 0 100 0 100 0 0 100 0 91 3 100 0 3 97
Clostridium
perfringens 73 100 0 100 0 100 0 100 0 100 0 0 100 0 96 0 99 1 100 0
C. difficilec
56 100 0 100 0 0 100 100 0 20 18 0 0 79 5 79 78 22 100 0
Other Clostridium
spp. 43 100 0 100 0 47 26 100 0 100 0 0 79 9 56 21 74 12 100 0
The Use of Data From External
Surveillance Programs
Antibiograms
SUMMARY • This guideline presents specific recommendations for
the collection, analysis, and presentation of cumulative antimicrobial susceptibility test data (antibiograms).
• Among the issues addressed are the way in which multiple isolates from the same patient should be handled, species to be included (or combined), the frequency of data analysis, and the format for data presentation.
• This guideline also identifies additional data analysis and presentation options that may be useful to certain clinicians for specialized applications.