The Very Latest from the CLSI AST Subcommittee.

Transcription

1 The Very Latest from the CLSI AST Subcommittee. Susan E. Sharp, Ph.D., DABMM, FAAM Director - Regional Laboratory Director - Regional Microbiology/Molecular Infectious Diseases Diagnostics Laboratory Kaiser Permanente Associate Professor - Department of Pathology Oregon Health & Sciences University Portland, OR

2 OBJECTIVES Review significant changes made in the 2012/2013 M100 documents. Review changes in this year s 2014 CLSI M100-S24 document. Discuss new developments for the January 2015 CLSI M100-S25 guideline. 2

3 CLSI AST Standards January 2014 M100-S24 Tables (2014)* M02-A11 Disk Diffusion Method (2012)^ M07-A9 MIC Method (2012)^ * M100 updated every year ^ M02, M07 updated every 3 years 3

4 Summary of Major Changes Changes to CLSI documents are summarized in the front of each document. Recent breakpoint addition/revision dates are listed in the front of M100 document. Information listed in boldface type is new or modified since the previous edition of M100 document. 4

5 Significant changes in

6 Staphylococcus spp. Penicillin The story.. > 90% of staphylococci are penicillin R Penicillin rarely considered for treatment of staphylococcal infections HOWEVER - Penicillin might be considered for infections requiring lengthy therapy (e.g., endocarditis, osteomyelitis) - IF penicillin were known to be S Some Staphylococcus spp. that test S to penicillin by MIC or disk diffusion may actually possess a β-lactamase (BL) that may cause the patient to fail penicillin therapy. 6

7 Staphylococcus spp. Penicillin CLSI Previous recommendation (2011): If the isolate tests S for penicillin, perform the induced nitrocefin BL test before reporting penicillin as S. Penicillin Breakpoints MIC (µg/ml) Zone (mm) S I R S I R PCR for the blaz gene (codes for BL) may be considered 7 Reference: M100-S21 (2011) - Table 2C. Page 70

8 Staphylococcus aureus (BL) Induced nitrocefin BL test usually, but not always, detects staphylococcal BLs Other BL tests are more sensitive for the detection of BL than the nitrocefin test: Cloverleaf test Penicillin disk zone edge test blaz gene PCR is also not optimal for BL As there are several types of blaz genes all types may not be detected by a single PCR assay 8

9 Staphylococcus aureus (BL) Induced nitrocefin BL test usually, but not always, detects staphylococcal BLs? Other BL tests are more sensitive for the detection of BL than the nitrocefin test: Cloverleaf test Penicillin disk zone edge test blaz gene PCR is also not optimal for BL As there are several types of blaz genes all types may not be detected by a single PCR assay? 9

10 Staphylococcus aureus (BL) Induced nitrocefin BL test usually, but not always, detects staphylococcal BLs? Other BL tests are more sensitive for the detection of BL than the nitrocefin test: Cloverleaf test Penicillin disk zone edge test blaz gene PCR is also not optimal for BL As there are several types of blaz genes all types may not be detected by a single PCR assay? 10

11 Cloverleaf Assay for BL in S. aureus BL negative 5% sheep blood agar S. aureus ATCC as the indicator organism 1 unit penicillin disk A Negative (pen-s) strain Isolates A-D are all BL + (pen-r) Some difficulties reading D C Cloverleaf B 11 Reference: CLSI Agenda Book January 2011.

12 β- lactamase positive β- lactamase negative 12

13 Staphylococcus aureus Disk Zone Edge Test (10 U penicillin disk and standard disk diffusion method) Fuzzy / beach = β-lactamase negative, Penicillin - S S. aureus supplemental QC: Neg - ATCC Sharp / cliff = β-lactamase positive, Penicillin - R Pos - ATCC Reference: M100-S22. Table 2C Supplemental Table 1. Page 83

14 Staphylococcus aureus 3 Lab BL Study Results (N=348), 2012 Test Sensitivity Specificity Cefinase 77% 100% Cloverleaf 100% 100% Penicillin disk zone edge 96% 100% 14 Reference: CLSI Agenda Book January, 2011

15 Staphylococcus spp. Penicillin Optional Strategy Report penicillin as R if tests resistant Suppress penicillin if it tests as S and consider a note: Contact laboratory if penicillin results needed. If penicillin results are needed, perform: Nitrocefin BL test (un-induced) If positive report as penicillin R If negative» Penicillin zone edge test > If Beach = Report Penicillin-S > If Cliff = Report Penicillin-R 15

16 Staphylococcus spp. Penicillin S. aureus Isolates where penicillin zones are 29 mm or penicillin MICs are 0.12 µg/ml, perform a penicillin disk zone edge test before reporting as penicillin susceptible. NOTE: S.lugdunensis isolates where penicillin zones are 29 mm or penicillin MICs are 0.12 µg/ml, perform an induced nitrocefin assay or other CLSI reference method on isolates before reporting as penicillin susceptible. The penicillin disk zone edge test was shown to be inferior as compared to the induced nitrocefin assay and should not be used with S.lugdunensis. 16

17 2012 Inducible clindamycin resistance in Streptococcus: b-streptococcus If performing susceptibility testing on these organisms, you should include inducible-clindamycin resistance testing. S.pneumoniae The clinical significance of this mechanism of clindamycin resistance is not known for S.pneumoniae, but inducible clindamycin resistance can be detected using D-zone testing. If testing S.pneumoniae to clindamycin and the isolate is clindamycin-s, a test for inducible clindamycin resistance should be performed. 17 October 29, Kaiser Foundation Health Plan, Inc. For internal use only.

18 18 NEW IN 2013

19 Staphylococcus All cephalosporins/many penicillins in the 2012 Table 2C were removed. Deleted all β-lactam breakpoints except penicillin, oxacillin [cefoxitin], and ceftaroline. A statement is provided to indicate that results for cephalosporins and other b-lactam antibiotics can be predicted from the results of penicillin, oxacillin MIC, cefoxitin MIC, or cefoxitin disk diffusion testing. 19

20 Staphylococcus spp. M100-S22, Table 2C.

21 Staphylococcus spp. M100-S22, Table 2C Eliminated breakpoints fo Penicillins BL/BL inhibitor combos Cephalosporins Carbapenems

22 Staphylococcus Rationale for deleting these breakpoints for staphylococci: The 2012 breakpoints were most likely inaccurate. They were Grandfathered into the staphylococcal tables with other major table over-hauls in the early 2000 s. Can deduce all anti-staphylococcal b-lactam results from penicillin and oxacillin [cefoxitin] results. 22

23 Staphylococcus spp. β-lactam Breakpoints Remaining Penicillin Represents penicillinase-labile penicillins Oxacillin (MIC only; no more DD) Represents penicillinase-stable penicillins Cefoxitin Surrogate for oxacillin Ceftaroline (added 2013) Cephem with anti-mrsa activity

24 Staphylococcus - β-lactams Use Pen and Oxa (FOX) results to predict results for other ß-lactams Penicillin S R R Test Results Oxacillin (cefoxitin) S S R Predicts Susceptible to: All penicillins ß-lac / ß-lactamase inhibitor combos Cephems Carbapenems Resistant to: Penicillinase-labile penicillins Susceptible to: Penicillinase-stable penicillins ß-lac / ß-lactamase inhibitor combos Cephems Carbapenems Resistant to: All ß-lactams (except cephems with anti-mrsa activity, e.g., ceftaroline) amoxicillin, ampicillin, carbenicillin,mezlocillin penicillin, piperacillin ticarcillin cloxacillin, dicloxacillin flucloxacillin, methicillin nafcillin, oxacillin

25 Staphylococcus - β-lactams Oxa (FOX) results to predict results for other ß-lactams Oxacillin Test Results Predicts S R (Do not report the penicillinase-labile penicillins) Susceptible to: Penicillinase-stable penicillins ß-lac / ß-lactamase inhibitor combos Cephems Carbapenems Resistant to: All ß-lactams (except cephems with anti-mrsa activity, e.g., ceftaroline) cloxacillin, dicloxacillin flucloxacillin, methicillin nafcillin, oxacillin

26 NEW 2013 AST QC Guidance Table 3C. Disk Diffusion: Reference Guide to QC Frequency Conversion from Daily to Weekly QC Routine QC is performed each day the test is performed unless an alternative quality control plan has been established. CLSI document M02-A11 Section 15.7 describes a QC plan using a day protocol that if successfully completed allows a user to convert from daily to weekly quality control. < 1/20 or < 3/30 weekly QC testing 26

27 NEW AST QC: 3x5 (15) Plan Statistics Out-of-control results could be due to either systemic or random errors Systemic errors = likely to get >2 outliers out of 15 results Random (allowable) errors = very high probability of getting 1 outlier of 15 results due to random error (which is OK) 1/15 error: Deemed likely a random error >2/15 errors: Deemed possible systematic error continue tests <3/30 errors: Deemed likely random error >4/30 errors: Deemed likely systematic error investigate 27

28 NEW AST QC 3x5 (15) Plan Test 3 replicates of each QC strain for 5 days using individually prepared inoculum 0-1 of 15 out of range? Pass. Convert to weekly QC. 2-3 of 15 out of range? Test another 3 replicates for 5 days > 4 of 15 out of range? Fail. Continue to include QC each test day. Take corrective action. TOTAL: 2-3 of 30 out of range? > 4 of 30 out of range? 28 Pass. Convert to weekly QC.

29 Intrinsic Resistance Tables: 2013 Enterobacteriaceae Added imipenem with note that Proteus species, Providencia species and Morganella species may have elevated MICs by mechanisms other than by production of carbapenemases. Isolates that test S should be reported as S. Added in a Note 2 information that Enterobacteriaceae are also intrinsically resistant to clindamycin, daptomycin, fusidic acid, glycopeptides (vancomycin, teicoplanin), linezolid, macrolides (erythromycin, clarithromycin, azithromycin), quinupristindalfopristin, and rifampin. Added Non-Enterobacteriaceae Added Staphylococci Added Enterococcus spp. 29

30 NEW IN

31 Vancomycin / Staphylococci 2014 Table 2C: Vancomycin disk diffusion Previously you could use it for detecting R VRSA due to the vana gene will show no zone of inhibition around a 30-mg vancomycin disk Any isolate with > 7mm zone must be tested with a MIC method before reporting as S 31

32 - Staphylococcus species No DD criteria! 32

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35 - Staphylococcus species No DD criteria! 35

36 Streamlined QC 2014 Routine QC recommendations/organism: Those that appear for each organism group will be streamlined. These new guidelines can be used for both weekly QC as well as individual drug QC. 36

37 P.aeruginosa : Table 2B-1 CURRENT: Routine QC Recommendations (See Tables 3A and 4A for acceptable QC ranges.) Escherichia coli ATCC Pseudomonas aeruginosa ATCC Escherichia coli ATCC (for b-lactam/b-lactamase inhibitor combinations) NEW for 2014: Routine QC Recommendations (See Tables 3A and 4A for acceptable QC ranges.) Escherichia coli ATCC Pseudomonas aeruginosa ATCC Escherichia coli ATCC (for b-lactam/b-lactamase inhibitor combinations) 37

38 Acinetobacter : Table 2B-2 CURRENT: Routine QC Recommendations (See Tables 3A and 4A for acceptable QC ranges.) Pseudomonas aeruginosa ATCC Escherichia coli ATCC Escherichia coli ATCC (for b-lactam/b-lactamase inhibitor combinations) NEW for 2014: Routine QC Recommendations (See Tables 3A and 4A for acceptable QC ranges.) Pseudomonas aeruginosa ATCC Escherichia coli ATCC (for tetracyclines and SXT) Escherichia coli ATCC (for b-lactam/b-lactamase inhibitor combinations) 38

39 Burkholderia : Table 2B-3 Stenotrophomonas : Table 2B-4 CURRENT: Routine QC Recommendations (See Tables 3A and 4A for acceptable QC ranges.) Pseudomonas aeruginosa ATCC Escherichia coli ATCC Escherichia coli ATCC (for b-lactam/b-lactamase inhibitor combinations) NEW for 2014: Routine QC Recommendations (See Tables 3A and 4A for acceptable QC ranges.) Pseudomonas aeruginosa ATCC Escherichia coli ATCC (for chloramphenicol, minocycline, and SXT) Escherichia coli ATCC (for b-lactam/b-lactamase inhibitor combinations) 39

40 Other non-enterobacteriaceae : Table 2B-5 CURRENT: Routine QC Recommendations (See Tables 3A and 4A for acceptable QC ranges.) Pseudomonas aeruginosa ATCC Escherichia coli ATCC Escherichia coli ATCC (for b-lactam/b-lactamase inhibitor combinations) NEW for 2014: Routine QC Recommendations (See Tables 3A and 4A for acceptable QC ranges.) Pseudomonas aeruginosa ATCC Escherichia coli ATCC (for chloramphenicol, tetrayclines, sulfonamide and SXT) Escherichia coli ATCC (for b-lactam/b-lactamase inhibitor combinations) 40

41 Enterobacteriaceae : Table 2A CURRENT: Routine QC Recommendations (See Tables 3A and 4A for acceptable QC ranges.) Escherichia coli ATCC Escherichia coli ATCC (for b-lactam/b-lactamase inhibitor combinations) NEW for 2014: Routine QC Recommendations (See Tables 3A and 4A for acceptable QC ranges.) Escherichia coli ATCC Escherichia coli ATCC (for b-lactam/b-lactamase inhibitor combinations) Pseudomonas aeruginosa ATCC (carbapenems) 41

42 Enterobacteriaceae and cefepime ISSUE: When the cephalosporin breakpoints to the Enterobacteriaceae were change (lowered) in 2010, cefepime was also reviewed but the committee at that time left the breakpoint unchanged at < 8 / 16 / > 32 ug/ml. RESULT: The committee after MUCH discussion in 2013 voted to change cefepime breakpoints for the Enterobacteriaceae for M and introduce SDD. Previous 2013 Method Susceptible Intermediate Resistant MIC 8 µg/ml 16 µg/ml 32 µg/ml Zone Diameter (Disk Diffusion) 18 mm mm 14 mm Revised 2014 Susceptible-Dose Method Susceptible Dependent Resistant MIC 2 µg/ml 4 8 µg/ml 16 µg/ml Zone Diameter (Disk Diffusion) 25 mm mm 18 mm

43 SDD Cefepime Breakpoint Change for Enterobacteriaceae and Introduction of the Susceptible-Dose Dependent (SDD) Interpretive Category Pages of the 2014 M100-S24 (discussion of this new reporting criteria)

44 Cefepime SDD Why were the cefepime breakpoints reconsidered ( )? The issue of new breakpoints for cefepime became apparent for several reasons: Previous breakpoints were based on a higher dose of cefepime than is often used. Clinical failures were noted for isolates with cefepime MICs of 4 and 8 µg/ml, especially when lower doses of cefepime were used. There are limited new drugs in the pipeline that show activity against multidrug-resistant gram-negative bacteria: There is a need to optimize use of drugs currently available. Designing susceptibility reports to correlate better with dosages of the drug used is one way to help accomplish this goal.

45 Interpretive Criteria Susceptible Dose Dependent Definition: The SDD category implies that susceptibility of an isolate is dependent on the dosing regimen that is used in the patient. In order to achieve levels that are likely to be clinically effective against isolates for which the susceptibility testing results are in the SDD category, it is necessary to use a dosing regimen that results in higher drug exposure than the dose that was used to establish the susceptible breakpoint. Consideration should be given to the maximum approved dosage regimen, because high exposure gives the highest probability of adequate coverage of an SDD isolate.

46 Cefepime SDD Accompanying NOTE states: The SDD interpretation is a new category for antibacterial susceptibility testing, although it has been previously applied for interpretation of antifungal susceptibility test results (see CLSI document M27-S4). The concept of SDD has been included within the intermediate category definition for antibacterials. However, this is often overlooked or not understood by clinicians and microbiologists when an intermediate result is reported. The SDD category may be assigned when doses well above those used to calculate the susceptible breakpoint are approved and used clinically, and where sufficient data to justify the designation exist and have been reviewed. When the intermediate category is used, its definition remains unchanged.

47 Cefepime SDD NOTE: The SDD interpretation is a new category for antibacterial susceptibility testing, although it has been previously applied for interpretation of antifungal susceptibility test results (see CLSI document M27-S4). The concept of SDD has been included within the intermediate category definition for antibacterials. However, this is often overlooked or not understood by clinicians and microbiologists when an intermediate result is reported. The SDD category may be assigned when doses well above those used to calculate the susceptible breakpoint are approved and used clinically, and where sufficient data to justify the designation exist and have been reviewed. When the intermediate category is used, its definition remains unchanged.

48 Cefepime SDD SDD is recommended instead of intermediate when reporting cefepime results for Enterobacteriaceae isolates because: There are multiple approved dosing options for cefepime, and SDD highlights the option of using higher doses to treat infections caused by isolates when the cefepime MIC is 4 or 8 µg/ml or the zone is 19 to 24 mm.

49 Cefepime SDD Why is SDD being used now? It has become apparent that there is a growing need to refine susceptibility reporting to maximize clinicians use of available drugs. Intermediate too often means resistant to clinicians because they do not appreciate the full definition of intermediate. SDD is more specific and it conveys what we know a higher dose can be considered for isolates with MICs (or zones) that fall in this interpretive category. SDD is already well established for use in antifungal susceptibility testing. It is anticipated that reporting a cefepime SDD result will encourage clinicians to consider the possibility that cefepime may be an option for treatment. Antibiotic stewardship programs, which emphasize dosing regimen and duration of therapy options, are increasing awareness of appropriate use of antibiotics. Personnel from these programs should be able to describe the significance to clinicians of an SDD result for cefepime.

50 Cefepime SDD How should this change be implemented? Meet with the appropriate practitioners at your institution (members of the antimicrobial stewardship team, infectious disease staff, pathology group, pharmacy, etc.) to inform them of these changes and agree on a plan to inform your clinicians of this change. Talk to the manufacturer of your antimicrobial susceptibility testing device to determine how to implement the revised breakpoints on your device. NOTE: Because the US Food and Drug Administration (FDA) has not revised the cefepime breakpoints and commercial manufacturers must use FDA breakpoints, the manufacturer cannot adopt the new CLSI cefepime breakpoints. However, for most systems, you can manually change the breakpoints and implement following a verification study. Work with your laboratory information system staff to report SDD or D for Enterobacteriaceae when the cefepime MIC is 4 or 8 µg/ml. Make certain that SDD will be transmitted to the hospital information system and appropriately displayed on reports viewed by clinicians. Distribute user-specific educational materials to laboratory staff and clinicians receiving antimicrobial susceptibility testing results from your laboratory. Examples of these materials can be found on the CLSI Subcommittee on Antimicrobial Susceptibility Testing webpage at

51 What coming in 2015? 51 October 29, Kaiser Foundation Health Plan, Inc. For internal use only.

52 Quality Control - Continuing to look at ways to decrease routine QC testing 52

53 Out-of-Range QC 2015 (p M100-S24) Currently = The M2/M7 text and flowchart clearly indicates that you must perform 5 consecutive days of repeat QC if you can not attribute the out-of-range result to a specific issue. If you can contribute it to a particular issue (e.g., contamination, used the wrong QC strain, etc.), you only have to do one repeat and if in, you may continue weekly QC testing. However, the above does not address the 0-5% of out-of-range results which would be expected due to random error (as ranges are established based on > 95% agreement). 53 One suggestion is to use retrospective data from the same lot of materials to satisfy the 5 replicate repeat. This would not be a "statistical" change, only a change in approach. Also considering to allow for multiple replicates in one day to determine more quickly if there is a problem (as laboratories may still be testing patient specimens while troubleshooting).

54 Out-of-Range QC 2015 Adding a new section in M2/M7 for Troubleshooting out-of-range results: If the cause can be identified Correct the issue, document the reason, and retest the strain on the day the error is observed. If the repeated result is within range, no further corrective action is required. If the cause can not be identified - If the 4 previous QC results have been acceptable using the same lots of materials (e.g., agar plates, disks, MIC trays/plates/panels), these 4 results, along with the current repeat, may be used to retrospectively satisfy the requirement for 5 repeats. 54

55 Out-of-Range QC 2015 Example - If the cause can not be identified: If the 4 previous QC results were acceptable (same lots) and you now obtain an out-of-range result, repeat the QC as soon as possible and if this repeat is within range, the corrective action was successful and you can resume weekly testing. If the repeat is out-of-range you must take additional corrective action, and daily QC must be continued until the problem is resolved. If 4 previous QC results were not acceptable or not available (e.g., new lot recently put into use), test sufficient QC replicates to satisfy the requirement for a total of 5 results. Up to 3 QC replicates can be tested/day if individual inocula are used. 55

56 Example 1 - Cause can not be identified E.coli ATCC ampicillin: range 2-8 ug/ml If you have an out of range QC result upon weekly QC testing, you will be able to repeat the QC once - if in range, and if the last 4 times you previously tested were also in range (same lot #s) you can go back to weekly QC testing (example below). Week Day MIC panel Lot # Results Action 1/1 Mon /8 Mon /15 Mon /22 Mon /29 Mon Out of range. Repeat QC testing same day. 1/30 Tues In range. 5/6 acceptable in range QC tests for E.coli ATCC and ampicillin with lot Resume weekly QC testing. 56

57 Example 2 - Cause can not be identified E.coli ATCC ampicillin: range 2-8 ug/ml You may also repeat the QC testing prospectively - do as many as you need to get the 5/6 to be in range (same lot #s) (e.g.; 2 retrospective and 3 prospective). If all within range, you and can go back to weekly QC (example below). Week Day MIC panel Lot # Results Action 1/1 Mon /8 Mon /15 Mon /22 Mon Out of range. Repeat QC testing same day. 1/22 Tues In range. 3 acceptable in range QC tests for E.coli ATCC and ampicillin with lot Repeat QC for 2 more consecutive days. 1/22 Wed In range. 1/22 Thur In range. 5/6 acceptable in range QC tests for E.coli ATCC and ampicillin with lot Resume weekly QC testing. 57

58 Example 3 - Cause can not be identified E.coli ATCC ampicillin: range 2-8 ug/ml You may also do up to 3 replicates per day (same lot #s) using different starting dilutions (example below). Week Day Lot # Results Action 1/1 Mon /8 Mon /15 Mon /22 Mon Out of range. Repeat QC testing x3 same day from different starting dilutions. 1/22 Tues (1 st ) replicates from different starting dilutions 1/22 Tues (2 nd ) are in range. 5/6 acceptable in range QC tests for E.coli ATCC and ampicillin 1/22 Tues (3 rd ) with lot Resume weekly QC testing. 58

59 Streamlined QC 2015 M2/M7 (?) Using retrospective data to go to weekly testing: If you have been performing intermittent QC testing of a drug each time you test patient organisms, you will be able to use those contemporary (within the last year) retrospective results in order to collect data that can be used for going to weekly QC testing. For example, if you have QC tested a drug approximately 2x/month for the last year (but requests are starting to pick up), you can use the most recent 20 QC tests to document your ability to go to weekly QC testing for the drug. 59

60 Streamlined QC 2015 M2/M7 (?) Date tested LOT # disk/mha Results OK (Y/N) 11/13/13 123/258 Y 12/12/13 123/456 Y 12/22/13 123/456 Y 1/1/14 123/003 Y 1/15/14 456/003 Y 1/29/14 456/003 Y 2/5/14 456/225 Y /225 Y 20 days consecutive QC testing days = all acceptable begin weekly QC 3/3/14 456/258 Y 3/26/14 456/258 Y 4/16/14 456/459 Y 4/20/14 788/459 Y 5/1/14 788/459 Y 5/17/14 788/560 Y 6/6/14 788/560 Y 6/18/14 788/777 Y 7/3/14 788/777 Y 7/30/14 909/777 Y 8/16/14 909/889 Y 60 8/25/14 909/889 Y

61 Salmonella M100-S15 The pefloxacin (5ug) disk test was approved to screen for fluoroquinolone resistance for use in countries that cannot readily perform MIC testing. Screening breakpoint were approved at <23mm (resistant), >24mm (susceptible). The M100 will state that the pefloxacin disk test is the preferred method for fluoroquinolone resistance screening in Salmonella spp.; however, these disks are not currently available in the U.S. and may not be for some time. Breakpoints for azithromycin with Salmonella Typhi were approved for resistant isolates seen (1 o outside the US). The new breakpoints will be published in 2015 M100 document and will be: <16mg/ml (>13mm)-Susceptible; >32mg/ml (<12mm)-NonSusceptible 61 October 29, Kaiser Foundation Health Plan, Inc. For internal use only.

62 M-45 Guideline third edition: Revisions will be coming in this third edition for susceptibility testing with fastidious organisms. Includes 5 new organism groups (Lactococcus, Micrococcus and assorted related genera [Kocuria, Nesterenkonis, Dermacoccus and Kytococcus spp.], Rothia, Aerococcus and Gemella). Other existing groups will have additional antibiotics added or modified. Plesimonas shigelloides will be moved to the M100 document (enterobacteriaceae) and out of the Aeromonas group in M-45. Will look to harmonize the b-lactam breakpoints of Aeromonas to those of the Enterobacteriaceae in the M100 document. 62 October 29, Kaiser Foundation Health Plan, Inc. For internal use only.

63 SDD - Susceptible Dose-Dependent The CLSi will consider developing SDD breakpoints for the following b-lactam antibiotics with the enterobacteriaceae: aztreonam cefotaxime ceftriaxone cefoxitin ceftazidime They will also consider the possibility of developing SDD breakpoints with Pseudomonas aeruginosa: ceftazidime aztreonam cefepime 63 October 29, Kaiser Foundation Health Plan, Inc. For internal use only.

64 Carbapanemase detection The CLSI will develop the CarbaNP as a standardized reference test for detection of carbapenemases in GNRs. It is based on in vitro hydrolysis of carbapenems by bacteria containing carbapenems, which is detected by a changes in ph using the indicator phenol red [red (-) to yellow(+)]. This standardized protocol should be published in the 2015 M100-S15 guidelines.

65 M100 document - miscellaneous: Will remove 12 drugs from Table 1 ( antimicrobials suggested for routine testing and reporting ) in the M100-S15 document as they are no longer available for use in the U.S. The CLSI will also be looking at placing new, clarified information (with pictures!) for reading trailing endpoints in broth microdilution microtiter tray assays. The 2015 M100-S15 document will have an updated national anaerobe antibiogram table (from isolates testing from ). 65 October 29, Kaiser Foundation Health Plan, Inc. For internal use only.

66 New Antibiotics Oritavancin A new lipogycopeptide antibiotic for use in acute soft skin and tissue infections caused by resistant Gram positive cocci. It is reported that this drug may be given as a single bolus dose that may work as well as 7-10 days of twice daily vancomycin therapy for these organisms. The committee may look to see if a vancomycin disk testing might work as a screening test for susceptibility to this new antibiotic. 66 October 29, Kaiser Foundation Health Plan, Inc. For internal use only.

67 Remember this? Staphylococcus 2013 All cephalosporins/many penicillins in the 2012 Table 2C were removed for Deleted all β-lactam breakpoints except penicillin, oxacillin [cefoxitin], and ceftaroline. A statement is provided to indicate that results for cephalosporins and other b-lactam antibiotics can be predicted from the results of penicillin, oxacillin MIC, cefoxitin MIC, or cefoxitin disk diffusion testing. Oxacillin Test Results S R Predicts Susceptible to: Penicillinase-stable penicillins ß-lac / ß-lactamase inhibitor combos Cephems (= cephalosporins) Carbapenems Resistant to: All ß-lactams (except cephems with anti-mrsa activity, e.g., ceftaroline) 67

68 MSSA and Ceftriaxone Etest issue: CLSI & ASM White Paper A recent paper Pickering, et al, ( Common Occurrence of Ceftriaxone- Resistant, Methicillin-Sensitive Staphylococcus aureus at a Community Teaching Hospital ), published in Clinical Infectious Diseases has been RETRACTED. The paper reported that although the rate of ceftriaxone resistance in methicillin-susceptible S.aureus (MSSA) in the literature is ~3%, at their institution 60% of MSSA isolates tested non-susceptible to ceftriaxone. The authors went on to state that ceftriaxone susceptibility cannot be predicted by testing oxacillin (or cefoxitin) as suggested by the CLSI M100- S23 document Indication that they found MICs to oxacillin of <0.5 mg/ml in all of their ceftriaxone-r isolates. They concluded that MSSA isolates should be tested for susceptibility to ceftriaxone before this agent is used to treat serious MSSA infections. Again, this article has been RETRACTED. 68 October 29, Kaiser Foundation Health Plan, Inc. For internal use only.

69 MSSA and Ceftriaxone Etest issue: CLSI & ASM White Paper The reason behind this retraction is that the authors used Etest to perform ceftriaxone MIC testing on the MSSA isolates (did not use standardized microbroth dilution [BMD] methods). Based on additional studies, it is now apparent that the ceftriaxone Etest will over call resistance in MSSA as compared to standardized BMD testing. The CDC acquired 16 of the MSSA/ ceftriaxone non-susceptible isolates from the Pickering study. These 16 isolates were tested by ceftriaxone BMD at the CDC and all of the isolates had results in the susceptible range (MIC range 2-4mg/mL). Although there are no current CLSI breakpoint MIC values for ceftriaxone with the staphylococci (the 2012 CLSI M100 breakpoint for susceptible was <8mg/mL), the FDA susceptible breakpoint for ceftriaxone with staphylococci is <4mg/mL. 69 October 29, Kaiser Foundation Health Plan, Inc. For internal use only.

70 MSSA and Ceftriaxone Etest issue: CLSI & ASM White Paper In addition, the microbiology laboratory at Massachusetts General Hospital (MGH) did additional studies with 30 MSSA from their patient population with ceftriaxone. BMD MIC: 29/30 isolates MIC of 2 or 4 (1 isolate had an 8mg/ml) when tested Etest: all isolates had MIC results as follows: 4 mg/ml (3 isolates) 8 mg/ml (14 isolates) 16 mg/ml (9 isolates) >32 mg/ml (4 isolates) Per FDA breakpoints; 17/20 isolates non-s/cro Thus, the Etest showed many major errors as compared to BMD testing and should not be used to test staphylococci to ceftriaxone. It should also be pointed out that the ceftriaxone Etest is not approved for testing against Staphylococcus isolates in US. 70 October 29, Kaiser Foundation Health Plan, Inc. For internal use only.

71 MSSA and Ceftriaxone Etest issue: CLSI & ASM White Paper FDA breakpoint: < 4 Previous 2012 CLSI breakpoint: < 8 Massachusetts General Hospital Study 71 October 29, Kaiser Foundation Health Plan, Inc. For internal use only.

72 Take home MSSA and Ceftriaxone Etest issue: CLSI & ASM White Paper A recent paper (Pickering, et. al.) published in CID stating that MSSA isolates were 60% resistant to ceftriaxone HAS BEEN RETRACTED. Current CLSI M100 documents stating that oxacillin (cefoxitin) testing can be used for predicting the susceptibility of ceftriaxone for staphylococci can and should be used. The ceftriaxone Etest is not FDA approved for testing against staphylococci and will overcall resistance in MSSA if used. There is a need for reference confirmatory testing of any new resistance seen. 72 October 29, Kaiser Foundation Health Plan, Inc. For internal use only.

73 Summary - CLSI updates AST tables (M100) each January. CLSI updates documents that describe how to perform reference disk diffusion (M02) and reference MIC (M07) tests every 3 years (new ones due out in 2015). Changes to CLSI documents are summarized in the front of each document. Information listed in boldface type is new or modified since the previous edition. Recent breakpoint addition/revision dates are listed in the front of M100. Minutes of CLSI AST Subcommittee meetings and other materials are available at 73

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78 CLSI Watch for the January 2015 M100-S25 document! 78

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