# Presentation: 562368

## What’s New in the 2006 Standards for Antimicrobial Susceptibility Testing (AST)?

**Janet Hindler, MCLS MT(ASCP)**
**UCLA Medical Center**
_**[jhindler@ucla.edu](mailto:jhindler@ucla.edu)**_
***“******working as a consultant with the Association of***
***Public Health Laboratories with support from CDC******”****** ***

**1**

## At the conclusion of this talk, you will be able to......

**Outline the ****major changes**** found in the new CLSI tables (M100-S16) and standards for disk diffusion (M2-A9) and MIC testing (M7-A7).**
**Discuss how to optimally use the new Disk Diffusion and MIC QC ****Troubleshooting Guides.**
**Describe a strategy for ****implementing**** the new practice guidelines in your laboratory, as appropriate.**

**2**

## CLSI Standards - 2006

**M100-S16 Tables ****(2006)***
**	****...****..to be used with text documents explaining how to perform the tests....**
**	****	****M2-A9   Disk Diffusion**** (2006)****
**	****	****M7-A7   MIC**** (2006)****

- New!

*** M100 updated yearly**
****M2, M7 updated every 3 years**

**3**

## Reference Terminology

**...****.when I refer to....**
**M100 ****-- this means the new tables M100-S16**
**M2**** -- this means the new disk diffusion document M2-A9**
**M7**** -- this means the new MIC document M7-A7**
**M45**** -- this means the new fastidious organism testing document M45-P**
**CLSI**** = formerly ****NCCLS****	****	**

**4**

## CLSI M100 contains.....

**this edition**

**M2 Tables **
**Disk Diffusion**

**M7 Tables**
**MIC**

**Glossary**
**I & II**

**Answers to **
**user questions**

**CLSI M100 contains.....**

**Test/report**
**Breakpoints**
**QC**

**M100**
** **

**Test/report**
**Breakpoints**
**QC**

**5**

## Updated information in M100-S16

**Updated information in M100-S16**

**6**

## Changes 2006 CLSI M100-S16

- CLSI

**7**

## CLSI Standard Reference  Method and Breakpoints (M100-S16, page 14)

**CLSI Standard Reference  Method and Breakpoints (M100-S16, page 14)**

**8**

## CLSI M2, M7, M100

**Describe standard consensus ****“reference methods”**
**U.S. clinical labs can use:**
**CLSI test method as written**
**Method that performs comparably to CLSI ****“reference  method” ****(e.g. FDA-cleared diagnostic AST device)**

**Diagnostic AST device = commercial instrument or test used to determine antimicrobial susceptibility in vitro**

**9**

## 10

**Testing to establish ****FDA breakpoints**** done using CLSI “standard reference methods”**

**Submits “New Drug Approval” (NDA) request packet  to FDA**
**  ****-clinical outcome data**
**  ****-microbiological data**
**     ****-****breakpoints**
**     ****-QC ranges**
**  ****-other**

**Therapeutic details provided in pharmaceutical product labeling; includes ****FDA breakpoints**

**Submits diagnostic AST device performance data to FDA**

**Diagnostic AST device performance data is based on manufacturer demonstrating that their device produces results comparable to results produced with CLSI “standard reference methods”**

**If FDA approved**

**Testing details provided in diagnostic AST device product labeling;  includes ****FDA breakpoints**

**If FDA approved**

**Testing details and ****CLSI breakpoints**** provided in laboratory testing “reference standards”....CLSI M2, M7 and M100**

**If CLSI approved**

**Submits condensed version of NDA request packet to CLSI**
**  ****-clinical outcome data**
**  ****-microbiological data**
**     ****-****breakpoints**
**     ****-QC ranges**
**  ****-other**

**New Antimicrobial Agent Pathway**

**Diagnostic Manufacturer**
** **

**Pharmaceutical**
** ****Company**
** **

**10**

## FDA vs. CLSI Breakpoints

**Nearly always agree!**
**Sometimes ****disagree**
**Sometimes ****only FDA breakpoints**** (e.g. tigecycline)**
**Sometimes ****only CLSI breakpoints**** (before drug is FDA cleared or if drug used in other countries) **
**Sometimes ****modified by CLSI**** (e.g., 2006, vancomycin – *****S. aureus*****)**

**11**

## 2006 Vancomycin MIC (μg/ml) Breakpoints – S. aureus

**≤****2   4-8  ********16**

**FDA**
**≤****4   8-16  ********32**

**Presently, diagnostic manufacturers must use ****FDA breakpoints**

**Clinical laboratories can use ****CLSI**** or ****FDA**** ****breakpoints**
**Caveat:**** if using commercial AST instrument, system uses ****FDA breakpoints**

**2006 Vancomycin MIC (****μ****g/ml) Breakpoints – *****S. aureus***

**12**

## CLSI Introduction to 

**Tables 1-1B; 2A-2L**

**13**

## CLSI Introduction to Tables “Clinical Indications”

**	****“****These guidelines are based on drugs with **_**clinical indications approved by the**__** **__**Food & Drug Administration (FDA) in the United States**_**. In other countries, placement in Tables 1 and 1A of antimicrobial agents should be based on available drugs approved for clinical use by relevant regulatory agencies.”**

**CLSI M100-S16; Introduction**_ _**(M2, M7)**

**14**

## Example of Drug Labeling

**Daptomycin product labeling...**
- _[http://www.cubicin.com/PDF/1004-2_MARKETING_gt.pdf](http://www.cubicin.com/PDF/1004-2_MARKETING_gt.pdf)__._

**Example of Drug Labeling**

**15**

## Drug product labeling....

**Has many ****sections****, including...**
**(Clinical) indications and usage**
**Based on demonstrated clinical efficacy**
**Examines in vitro susceptibility test and clinical outcome data**
**Microbiological activity**** (in vitro)**
**Does not mean clinical efficacy**
**Provides ****information**** for**
**Clinicians**
**Pharmacists**
**Diagnostic AST manufacturers**
**Patients**
**Others**

**16**

## “Clinical Indication and Usage”

**Clinical indication**** = a disease entity that has a specific set of signs, symptoms and laboratory findings that can be described to clinicians in product labeling.**
**Example:****Daptomycin has ****clinical indication**** for complicated skin and skin structure infections **
**This means...**
**Daptomycin can be used to treat *****S. aureus *****(including MRSA) wound infections as noted in package insert**
**Clinical indication**** is linked to ****specific pathogens**

**17**

## Daptomycin product labeling...

**Daptomycin product labeling...**
- _[http://www.cubicin.com/PDF/1004-2_MARKETING_gt.pdf](http://www.cubicin.com/PDF/1004-2_MARKETING_gt.pdf)__._

**18**

## Daptomycin product labeling...

**Daptomycin product labeling...**
- _[http://www.cubicin.com/PDF/1004-2_MARKETING_gt.pdf](http://www.cubicin.com/PDF/1004-2_MARKETING_gt.pdf)__._

**both in vitro and in clinical infections**

**in vitro**

**19**

## Daptomycin FDA MIC Breakpoints (same as CLSI)

**Daptomycin product labeling...**
- _[http://www.cubicin.com/PDF/1004-2_MARKETING_gt.pdf](http://www.cubicin.com/PDF/1004-2_MARKETING_gt.pdf)__._

**Daptomycin FDA MIC Breakpoints (same as CLSI)**
**2006 - CLSI eliminated disk diffusion breakpoints**

**20**

## CLSI Table 1 (M7)

**CLSI Table 1 (M7)**
** ****Drugs to Test/Report**

**21**

## Why are some drugs listed in Table 2 but not in Table 1?

***Why are some drugs listed in Table 2 but not in Table 1?***

**CLSI Table 1 (M7)**
** ****Drugs to Test/Report**

**CLSI Table 2B-1 (M7)**
** ****Non-Enterobacteriaceae Breakpoints**

**22**

## Possible Reasons why drug may be in Table 2 but not Table 1...

**Drug does ****not have an FDA clinical indication**** for organism**
**Drug may ****not be used**** in the USA **
**Drug is ****not a first-choice**** or alternative drug suggested for routine testing for organism**
**	****Example:**
**piperacillin-tazobactam and *****P. aeruginosa***

**23**

## Susceptible (“S”) Reworded

**New**** -...****implies that isolates are inhibited by the usually achievable concentrations of antimicrobial agent when the recommended dosage is used for the site of infection.**** **
**Old**** -...implies that an infection due to the strain may be appropriately treated with the dosage of antimicrobial agent recommended for that type of infection and infecting species, unless otherwise contraindicated.**

**CLSI M100-S16; Introduction**_ _**(M2, M7)**

**24**

## Intermediate (“I”)

**The “intermediate” category includes isolates with antimicrobial agent MICs that approach usually attainable blood and tissue levels and for which response rates may be lower than for susceptible isolates. The intermediate category implies clinical efficacy in body sites where the drugs are physiologically concentrated (e.g., quinolones and β‐lactams in urine) or when a **_**higher than normal***_** dosage of a drug can be used (e.g., β‐lactams). This category also includes a buffer zone, which should prevent small, uncontrolled, technical factors from causing major discrepancies in interpretations, especially for drugs with narrow pharmacotoxicity margins.**

***previously stated “****high dosage****”**

**CLSI M100-S16; Introduction**_ _**(M2, M7)**

**25**

## Resistant (“R”) Reworded

**New**** –...****implies that isolates are not inhibited by the usually achievable concentrations of the agent with normal dosage schedules and/or that demonstrate MICs that fall in the range where specific microbial resistance mechanisms are likely (e.g., ********-lactamases), and clinical efficacy of that agent against the isolate has not been  reliably shown in treatment studies.**** **
**Old**** - ...strains are not inhibited by the usually achievable systemic concentrations of the agent with normal dosage schedules and/or fall in the range where specific microbial resistance mechanisms (e.g., ****β****-lactamases) and clinical efficacy has not been reliable in treatment studies.**

**CLSI M100-S16; Introduction**_ _**(M2, M7)**

**26**

## “S” only Definition

**“****S” only Definition**

**rare occurrence**

**CLSI M100-S16; Introduction**_ _**(M2, M7)**

**27**

## “Absence” vs. “rare occurrence”.... How do we know if there has EVER been a “NS” isolate?

**Check CLSI M100-S16 ****“Suggestions for Verification of AST Results and Confirmation of Organism Identification”**** [Table 4 (M2) or Table 8 (M7)]**

**NS, not susceptible**

**28**

## Excerpt from: “Suggestions for Verification of AST Results and Confirmation of Organism Identification”

| 
Organism or Group | Category I
Verify at all labs | Category II
Verify – institution specific |
| --- | --- | --- |
| Staphylococcus aureus | daptomycin - NS
linezolid – NS
quin-dalfo – I or R
vancomycin – I or R | oxacillin – R |
| Streptococcus pneumoniae | fluoroquinolone - NS
linezolidc – NS
vancomycinc – NS | penicillin - R
3rd-gen cephalosporin- R |

**CLSI  M100-S16; Tables 4 (M2) and 8 (M7)**

**NS, not susceptible **
**Note: superscript “c” means “never reported”**

**29**

##  S. pneumoniae - Vancomycinc MIC (μg/ml)

**    ****	****	****    ****	****	**_**Susc**_**     **_**Int**_**      **_**Res**_
**vancomycin****	****  ****	******** 1.0****	****       -          -**
** **

**CLSI M100-S16; Table 2G (M7)**

*****_**investigate any NS isolate**_
**..Repeat ID and AST**
**..Save isolate**
**..Send to reference lab (test by CLSI MIC method)**
**Note:**** vancomycin-NS *****S. pneumoniae***** have NEVER been reported**

**c****NS  ****Example**
**NS, not susceptible**

**30**

##  S. aureus - Linezolid MIC (μg/ml)

**    ****	****	****    ****	****	**_**Susc**_**     **_**Int**_**      **_**Res**_
**linezolid****	****  ****	******** 4.0****	**** -****	****     -**
** **

*****_**investigate any NS isolate**_
**..Repeat ID and AST**
**..Save isolate**
**..Send to reference lab (CLSI MIC method)**
**Note:**** linezolid-NS *****S. aureus***** have been reported on rare occasions**

**NS  ****Example**
**NS, not susceptible**

**CLSI M100-S16; Table 2C (M7)**

**31**

## CLSI Introduction to Tables

**CLSI Introduction to Tables**
**Added ESBLs to “Warning” List**

**32**

## Clarification of Incubation Temperature Range

**35****°****C +/- 2****°****C (except staphylococci as shown below and *****Neisseria gonorrhoeae*****)**

**33**

## CLSI M45-P Guideline

**“****Methods for Antimicrobial Dilution and Disk Susceptibility Testing of Infrequently-Isolated or Fastidious Bacteria”**

- New!!

**34**

- Fresno 11/00

## CLSI M45-P Guideline

**“****Guideline”**** vs. ****“Standard”**
**M45 is....**
**Based upon data in published literature**
**Based on MIC distributions and resistance mechanisms of organisms**
**Limited clinical data available to support decisions**
**M100 is a ****“standard”**** and is based on substantial ****clinical data**** in addition to ****in vitro data ****(see CLSI M23)**
**“****P”**** = proposed; will likely become M45-****“A”**** (A= approved)**

**35**

## On inside cover of each CLSI document is description of Standard, Guideline, Proposed, Approved and more.... 

**On inside cover of each CLSI document is description of Standard, Guideline,** **Proposed, Approved and more.... **

**36**

## CLSI M45-P Guideline

| Abiotrophia / Granulicatella | Lactobacillus |
| --- | --- |
| *Aeromonas / Plesiomonas | Leuconostoc |
| Bacillus spp. (not anthrax) | Listeria monocytogenes |
| Campylobacter jejuni / coli | Moraxella catarrhalis |
| Corynebacterium | *Pasteurella |
| Erysipelothrix | Pediococcus |
| HACEK Group | *Vibrio spp. (not cholera) |

***disk diffusion method described in addition to MIC method**

**37**

## CLSI M45-P Guideline

**“****Testing should only be undertaken in consultation with ****infectious diseases or other expert clinicians**** that can assist in determining if susceptibility testing is needed in the management of a specific patient.”**

**CLSI M45-P; Indications**

**38**

## CLSI M45-P Table 5 Corynebacterium spp.

**CLSI M45-P Table 5 *****Corynebacterium *****spp.**

**39**

## CLSI M45-P Table 5  (con’t) Corynebacterium spp.

**CLSI M45-P Table 5  (con’t) *****Corynebacterium *****spp.**

**40**

## Changes 2006 CLSI M100-S16 Gram Negatives

- GNR

**41**

## Enterobacteriaceae

***CLARIFICATIONS...***
**ESBL screening breakpoints for***** ******Proteus mirabilis***
**Warning comment for***** ******Salmonella/Shigella***
**AST of *****Salmonella***** spp.**** from feces**

**42**

## Proteus mirabilis ESBL Screen Test

| Drug | Disk Screen 
(mm) | MIC Screen
 (μg/ml) |
| --- | --- | --- |
| Cefpodoxime | 17* | >1* |
| Ceftazidime | 22 | >1 |
| Aztreonam | NA |  NA |
| Cefotaxime | 27 | >1 |
| Ceftriaxone | NA | NA |

***unique for *****P. mirabilis***** (as compared to ****≤****22 mm and >4 ****μ****g/ml for *****E. coli***** and *****Klebsiella***** spp.); NA, not applicable**** **

**CLSI M100-S16; Table 2A (M2, M7)**

**43**

## “Warning” CommentSalmonella/Shigella

**“*****Warning*****: ****For *****Salmonella***** and *****Shigella***** spp., aminoglycosides, ****1****st**** - and ****2****nd**** -generation cephalosporins**** **_**and cephamycins**_** may appear active in vitro but are not effective clinically and should not be reported as “S”.**

**CLSI M100-S16; Table 2A (M2, M7)**

**44**

## CLSI Glossary I

**CLSI Glossary I**
** ****(Part 1)**
**Cephems**

**45**

## Salmonella Reporting 

_**When**_** ****fecal isolates**_** **_**of *****Salmonella***** and *****Shigella***** spp. **_**are tested**_** only ****ampicillin****, a ****quinolone****, and ****trimeth-sulfa**** should be tested and reported routinely. In addition, ****chloramphenicol**** and a ****3****rd****-generation cephalosporin**** should be tested and reported for extraintestinal isolates of *****Salmonella***** spp.**

**CLSI M100-S16; Table 2A (M2, M7)**

**46**

## Salmonella spp. (feces) 

**ampicillin****	****S**
**ciprofloxacin****	****S**
**trimeth-sulfa****	****S**

**Notes:**
**Add chloramphenicol (if your MDs want this) and 3****rd****-generation cephalosporin for extraintestinal isolates**
**May not need to do AST on *****Salmonella***** spp. isolated from patients with mild diarrhea as disease is self-limiting**

**47**

## Non-Enterobacteriaceae

**Added separate breakpoint tables:**
***Pseudomonas aeruginosa *****(disk diffusion)**
***Pseudomonas aeruginosa***** and other non-Enterobacteriaceae (MIC)**
***Acinetobacter***** spp.**
***Burkholderia cepacia***
***Stenotrophomonas maltophilia***
**Delete**** *****P. aeruginosa***** *****“Rx”***** comment**
**Colistin / polymyxin B**
**Deleted disk diffusion QC ranges**
**Added colistin MIC breakpoints for *****Acinetobacter***** spp*****. ***

**48**

## CLSI Table 1 (M7)

**CLSI Table 1 (M7)**
** ****Drugs to Test/Report**

**49**

## Table 2B-4 (M7)  MIC Breakpoints for Stenotrophomonas maltophilia

**Table 2B-4 (M7)  MIC Breakpoints for *****Stenotrophomonas maltophilia***

**50**

## S. maltophilia (blood)

**ceftazidime****	**** 32  R**
**levofloxacin****	****   2  S**
**minocycline****	****   1  S**
**ticarcillin-clav****	**** 16  S**
**trimeth-sulfa              0.5/9.5 S**

_**MIC (**__****__**g/ml)**_

**These are the only drugs for which there are MIC breakpoints in M100-S16 Table 2B-4 (M7)**

**51**

## What if MD asks for results for other drugs on S. maltophilia?

**Option to consider.....**
**Get request ****in writing****, preferably from Infectious Diseases clinician**
**Test by ****MIC**** only**
**Report results without ****interpretation**
**Qualify**** results**

**52**

## S. maltophilia (blood)

***aztreonam****	****   8**
**ceftazidime****	**** 32  R**
**levofloxacin****	****   2  S**
**minocycline****	****   1  S**
**ticarcillin-clav****	**** 16  S**
**trimeth-sulfa           ********0.5/9.5 S**

_**MIC (**__****__**g/ml)**_

***No MIC interpretive criteria available; reported per Dr. Jones request; Infectious Diseases consult suggested**

**Report **
**Option**

**53**

## Rx: Comment Deleted Pseudomonas aeruginosa

**“*****Rx:***** *****P. aeruginosa***** infections in granulo-cytopenic patients and serious infections in other patients should be treated with maximum doses of the selected antipseudomonal penicillin (carboxypenicillin or ureidopenicilllin) or ceftazidime in combination with an aminoglycoside.” **
**Rationale for deletion**** – there are currently other options for treatment  **

**CLSI M100-S16; Table 2B (M2, M7)**

**54**

## Colistin / Polymyxin B

**Currently, NO disk diffusion**** recommendations**
***Acinetobacter***** spp.**
**Breakpoints for ****other bugs**** forthcoming**
**No FDA-cleared**** test**

| Antimicrobial Agent | MIC (μg/ml) |  |  |
| --- | --- | --- | --- |
|  | S | I | R |
| Polymyxin B or colistin | ≤2 | - | 4 |

**CLSI M100-S16; Table 2B (M7)**

**55**

## Haemophilus spp. Neisseria meningitidis

**Procedures in M2, M7 and M100 are for *****H. influenzae *****and***** H. parainfluenzae***
**CLSI M45-P for other *****Haemophilus***** species**
***Neisseria meningitidis***
**Added disk diffusion procedure**

**56**

## Standard Disk Diffusion Method for                Neisseria meningitidis

**Standard Disk Diffusion Method for                *****Neisseria meningitidis***

- New!

**CLSI M100-S16; Table 2J (M2)**

**57**

## Neisseria meningitidisDisk Diffusion Testing

**Medium:****	****MHA with 5% sheep blood**
**Inoculum:****	****direct colony suspension equivalent ****	****to 0.5 McFarland standard**
**Incubation:****	****35********C +/- 2********C; 5% CO****2****; 20-24h**
**QC:****	*****S. pneumoniae***** ATCC 49619**
***	******E. coli***** ATCC 25922 (select drugs)**

**Biosafety Level 2 (BSL 2) safety practices; use biosafety cabinet**

**58**

## Neisseria meningitidisDisk Diffusion Testing

**Therapeutic agents***
*******Penicillin**
*******Ampicillin**
**Cefotaxime**
**Ceftriaxone**
**Meropenem**
**Chloramphenicol**

**All drugs listed are in Test/Report Group C “Supplemental, Report Selectively”**
***No disk diffusion breakpoints; must do MIC test**

**59**

## Neisseria meningitidisDisk Diffusion Testing

**“****Breakpoints may be appropriate only for ****prophylaxis**** of meningococcal case contacts”**
**Azithromycin**
**Ciprofloxacin**
**Minocycline**
**Nalidixic acid (for ****surveillance**** only; may detect diminished ****fluoroquinolone**** susceptibility)**
**Rifampin**
**Trimethoprim-sulfamethoxazole (predicts susceptibility to ****sulfonamides**** also)**

**All drugs listed are in Test/Report Group C “Supplemental, Report Selectively”**

**60**

## Changes 2006 CLSI M100-S16 Gram Positives

- GPC

**61**

## Daptomycin

**For.....**
**Staphylococcus**
**Enterococcus**
**Streptococcus**
**Deleted daptomycin disk diffusion breakpoints**
**Rationale for deletion**** – inability of disk diffusion method to consistently detect those few isolates that are non-susceptible to daptomycin**
**Specify ****agar dilution testing has not been validated**** for daptomycin **
**FDA-cleared**** for several commercial systems**

**62**

## Staphylococcus spp. 

***Clarifications...***
**For disk diffusion testing, ****cefoxitin disk**** is..**
**Preferred**** over oxacillin disk for detection of *****mec*****A-mediated resistance  **
**A ****“surrogate”**** for oxacillin (report oxacillin NOT cefoxitin)**
**Should always be used for *****S. lugdunensis***** (do not use oxacillin disk)**
**Fluoroquinolones**** – breakpoints for gatifloxacin, levofloxacin, moxifloxacin, and ofloxacin still tentative (for another year)****  **

**63**

## Cefoxitin Disk for mecA-mediated Resistance in Staphylococci

** ****	****	****   ****	****                   ****Cefoxitin zone (mm)**** **
**	****	****	****	****	****    **_**Res**_**	****           **_**Susc**_**	****             **
***     ******S. aureus*****               ********19***** ****               ********20********
**	****  *****S. lugdunensis ******	******    *********19***** ****               ********20********
**     ****CoNS****	****                    ********24*********                ********25********
*******	****Report as oxacillin resistant**
********	****Report as oxacillin susceptible**
**CoNS, coagulase-negative staphylococci**

**CLSI M100-S16; Table 2C (M2)**

**64**

## MIC Breakpoints (g/ml)Staphylococcus and Fluoroquinolones

|  | Old (M100-S14)* |  |  | M100-S15, M100-S16 ** |  |  |
| --- | --- | --- | --- | --- | --- | --- |
|  | S | I | R | S | I | R |
| Gatifloxacin | 2 | 4 | 8 | 0.5 | 1 | 2 |
| Levofloxacin | 2 | 4 | 8 | 1 | 2 | 4 |
| Moxifloxacin |  | none |  | 0.5 | 1 | 2 |

***Same as current FDA breakpoints**
****Tentative for another year **
**Check M100-S16 for corresponding disk diffusion breakpoints**

**65**

## Staphylococcus spp. 

***Additions/changes...***
**Modified ****vancomycin MIC breakpoints**** for *****S. aureus ***
**Table highlighting use of ****BHI-vancomycin agar**** for *****S. aureus***

**66**

## CLSI Vancomycin MIC (μg/ml) Breakpoints – S. aureus

**≤****2   4-8  ********16**

**2005**
**≤****4   8-16  ********32**

**CLSI Vancomycin MIC (****μ****g/ml) Breakpoints – *****S. aureus***

**Notes:**
**2005 same as current FDA breakpoints**
**No change in disk diffusion breakpoints**
**No change for coagulase-negative staphylococci**

**67**

## Why did CLSI modify vancomycin breakpoints for S. aureus?

**To detect ****emerging vancomycin resistance **
**Data shows patients ****fail vancomycin**** therapy when infected with *****S. aureus***** with vancomycin MICs of ********4 ****μ****g/ml**
**Clinical labs have been advised by CDC to investigate *****S. aureus***** with vancomycin ****MICs of ********4 ****μ****g/ml as potential VISA or VRSA**
**Some ****VISA test 4 ****μ****g/ml**** by some methods**

**68**

## Modifying CLSI Breakpoints

** ****CLSI has mechanism for reevaluation of breakpoints when needed as defined in ****CLSI M23-A2**** “Development of In Vitro Susceptibility Testing Criteria and QC Parameters”**

**69**

## Will it matter what vancomycin breakpoints we use for S. aureus?

**“****Either FDA or CLSI susceptibility interpretive breakpoints are acceptable to clinical laboratory accrediting bodies” ****(CLSI M100-S16, page 14)**
**...****and we should all pursue *****S. aureus***** with vancomycin MICs ********4 ****μ****g/ml since these could be VISA (or VRSA if ********16 ****μ****g/ml) **
**So, if we ****ALL diligently pursue vancomycin MICs of ********4 ****μ****g/ml in *****S. aureus,***** it really won’t matter**

**http://www.cdc.gov/ncidod/dhqp/ar_visavrsa_algo.html**

**70**

## S. aureus - Vancomycin MICs* UCLA 1/00-10/05 (n=13981)

***S. aureus***** - Vancomycin MICs* ****UCLA 1/00-10/05 (**_**n=13981**_**)**

***CLSI broth microdilution reference method**

**FDA “S” breakpoint**

**CLSI “S” breakpoint**

**71**

## S. aureus

**Add BHI-V screen if using automated system (unless fixed, check with manufacturer) or use CLSI MIC reference method or Etest to detect reduced susceptibility to vancomycin in *****S. aureus***
**For workup of VISA and VRSA, see ****http://www.cdc.gov/ncidod/dhqp/ar_visavrsa_algo.html**

**BHI-Vancomycin (6 ****μ****g/ml) Screen**

**72**

## VRSA (as of 12/05)

|  | MIC 
(ug/ml) 1 | Source | Date | Location |
| --- | --- | --- | --- | --- |
| 1 | 1024 | 	foot ulcer |  4/02 |  Michigan |
| 2 | 32 | 	foot ulcer | 9/02  |  Pennsylvania |
| 3 | 64 | 	nephrostomy tube | 3/04 |  New York |
| 4 | 256 | 	foot ulcer | 2/05 |  Michigan |
| 5 | 512 | 	wound | 10/05 |  Michigan |

** ****1**** Reference broth microdilution MIC**
** **

**73**

## Enterococcus spp. 

***Additions/changes...***
**Deleted vancomycin-synergy *****Rx***** comment**
**Added definitions  for  ****high-level aminoglycoside resistance (HLAR) testing for disk diffusion**** (similar to those for MIC testing)**

**74**

## Enterococcus Rx Comment Deleted

***Rx:***** If vancomycin is used for serious enterococcal infections, such as endocarditis, combined therapy with an aminoglycoside is usually indicated.**
**Rationale for deletion**** – use of vancomycin should not be encouraged;  ampicillin or penicillin are the preferred agents to use in combination therapy for enterococci**

**CLSI M100-S16; Table 2D (M2, M7)**

**75**

## Enterococcus spp.

***Enterococcus *****spp.**
**Disk diffusion screen for HLAR**

**76**

## Enterococcus spp.Disk diffusion Screen for HLAR

**Resistant ****-- will not be synergistic with cell-wall-active agent (e.g., ampicillin, penicillin, vancomycin)**
**Inconclusive ****-- perform an agar dilution or broth microdilution test to confirm**
**Susceptible**** -- will be synergistic with cell-wall-active agent (e.g., ampicillin, penicillin, vancomycin) that is also susceptible**

**CLSI M100-S16; Table 2D (M2)**

**77**

## Streptococcus pneumoniae Modified reporting recommendations for meropenem... 

**“****Penicillin **_**and**_** cefotaxime or ceftriaxone **_**or**_** meropenem should be tested by a reliable MIC method and reported routinely with ****CSF isolates of *****S. pneumoniae.******”***

**CLSI M100-S16; Table 2G (M2, M7)**

**78**

## New Antimicrobial Agents in M100-S16*

| Agent | Drug class | Route of administration | FDA approved |
| --- | --- | --- | --- |
| ceftobiprole | cephem | IV | No |
| faropenem | penem | PO | No |

***In Glossary and QC tables only**

## Ceftobiprole

**Manufacturer:**
**Johnson & Johnson**** **
**Possible clinical use:**
**Nosocomial pneumonia**
**Complicated skin and skin structure infections**

## Ceftobiprole (con’t)

**Microbiological activity:**
***Staphylococci***** (including MRSA)**
***Streptococci***** (including penicillin-R *****S. pneumoniae*****)**
***Enterococcus faecalis***
**Most *****Enterobacteriaceae ***
***Haemophilus influenzae *****(including BLNAR)**
**Many *****Pseudomonas aeruginosa *****and *****Acinetobacter baumanii***
**Limited activity:**
**Many non-*****Enterobacteriaceae *****[Gram-negatives]**
***Enterococcus faecium***
***ESBL-*****producers**
**Metallo-beta-lactamase producers**
**Beta-lactamase-producing anaerobes**

## Faropenem

**Manufacturer:**
**Replidyne**
**Possible clinical use:**
**Bacterial sinusitis**
**Acute exacerbations of chronic bronchitis**
**Community-acquired pneumonia**
**Uncomplicated skin and skin structure infections**

**82**

## Faropenem (con’t)

**Microbiological activity:**
**Respiratory pathogens***** (S. pneumoniae, H. influenzae, M. catarrhalis)***
***S. pyogenes***
**MSSA**
**Some *****Enterobacteriaceae***
**Limited activity:**
***Non-Enterobacteriaceae***
***Enterobacter *****spp*****.***
***Enterococcus faecium***
**MRSA**

**83**

## Changes 2006 CLSI M100-S16 Quality Assessment / Quality Control

- QA/QC

**84**

## Quality Control

***ADDITIONS / Changes...***
**Added ****QC ranges****:**
**Ceftobiprole**
**Faropenem****	**
**Drugs for testing***** ******Campylobacter jejuni***** ATCC 33560**** using broth dilution method**

**85**

## QC Tables

| Table | M2 (disk diffusion) | M7 (MIC testing) |
| --- | --- | --- |
| 3  | Nonfastidious | Nonfastidious |
| 3A | Fastidious | Fastidious (broth dilution) |
| 3B | DD QC Testing Frequency | Fastidious (agar dilution) |
| 3C | DD Troubleshooting Guide | Fastidious (broth dilution + supplement)* |
| 3D | NA | Fastidious (Brucella broth dilution)*    |

**DD, disk diffusion; NA, not applicable;**_** **_
***when testing potential agents of bioterrorism**

**86**

## QC Tables (con’t)

| Table | M2 | M7 |
| --- | --- | --- |
| 3E  | NA | MIC QC Testing Frequency |
| 3F | NA | MIC Troubleshooting Guide |

***NA, not applicable**

**87**

## Table 3C. Disk Diffusion QC Troubleshooting Guide

**Table 3C. Disk Diffusion QC Troubleshooting Guide**

- New!

**88**

## Disk Diffusion QC Troubleshooting Guide Table 3C (M2)  Examples:

| Antimicrobial Agent | QC Strain | Observation | Probable Cause | Comments / Action |
| --- | --- | --- | --- | --- |
| Beta-lactam group | Any | Zone initially acceptable but decreases and possibly out-of-range over time | Disk has lost potency | Use alternative lot of disks. Check storage conditions and package integrity.
Imipenem, cefaclor, and clavulanic acid are especially labile. |
| Quinolones | Any
 | Zone too large | pH of media too high | Acceptable pH range =7.2=7.4 |

**CLSI M100-S16; Table 3C (M2)**

**89**

## CLSI Standards - 2006

**M100-S16 Tables (2006)***
**	****...****..to be used with text documents explaining how to perform the tests....**
**	****	****M2-A9   Disk Diffusion**** (2006)****
**	****	****M7-A7   MIC**** (2006)****

- New!

*** M100 updated yearly**
****M2, M7 updated every 3 years**

**90**

## M2-A9, M7-A7 Primary Changes 

**Primarily ****expanded discussions and detailed recommendations**** for test procedures in M100-S16 including those for:**
**Oxacillin-resistant staphylococci**
***Streptococcus pneumoniae***
***Streptococcus *****spp*****.***
***Neisseria meningitidis***

**91**

## M2-A9, M7-A7 Primary Changes (con’t)

**Additions to ****antimicrobial agent descriptions **
**Additional tips for ****media/reagent preparation**
**Supplemental ****QC**** suggestions**

**92**

## Last pages of M2 and M7

**Summary of Comments and **
**Subcommittee Responses**

**93**

## Q&A Example (paraphrased)

**Q**** – Why is D zone test not recommended for *****Streptococcus pneumoniae*****?**
**A**** – Isolates of *****Streptococcus pneumoniae***** can have *****erm*****-mediated resistance to erythromycin. However, the vast majority of these are also resistant to clindamycin (constitutive phenotype). Rare isolates of ****pneumococci**** may have inducible resistance; however the clinical significance of this has not been established. Therefore, routine testing for inducible clindamycin resistance is not recommended for this species.**

**94**

## Issues Under Discussion by CLSI

**Additional recommendations for testing ****colistin / polymyxin B**
**Disk diffusion test for ****C*****ampylobacter***** spp. **
**Detection of ****ESBLs**
**Review recommendations for drugs to ****Test / Report (Table 1)**
**Improved communication ****of CLSI AST Subcommittee decisions **

**95**

## Material on your CD-ROM...

**PowerPoint presentation**
**PDF of “New Antimicrobial Agent Pathway” slide (slide #10)**
**M100-S16 checklist**
**References**
**CLSI information flier**
**CLSI catalogue**

**96**

## To Ask a Question....

**Please send to  **_**[neoffice@nltn.org](mailto:neoffice@nltn.org)**__**  **_
**Questions will be compiled and answers will be published on **_**[http://www.phppo.cdc.gov/nltn/nphtcs/ast012506.aspx](http://www.phppo.cdc.gov/nltn/nphtcs/ast012506.aspx)**__** **_

**97**

## Acknowledgements

**Boston NLTN Office**
**Shoolah Escott**
**Denise Korzeniowski**
**Vicente Mejia**
**Elizabeth Szymczak**
**CLSI Staff**
**	**

**Also**
**Mary Jane Ferraro**
**Jim Jorgensen**
**Susan Munro**
**John Powers**
**Jana Swenson**
**Fred Tenover**

***Financial support for this program is generously provided by Ortho McNeil Pharmaceutical***

**98**

## NLTN

**http://www.phppo.cdc.gov/nltn/default.aspx**

**NLTN**

**99**

## Thank you!

**100**