Contemporary Issues in Antimicrobial Contemporary Issues in Antimicrobial Susceptibility Testing (AST) for Susceptibility Testing (AST) for

Public Health Laboratories!Public Health Laboratories!

Janet Hindler, MCLS MT(ASCP)Janet Hindler, MCLS MT(ASCP)UCLA Medical CenterUCLA Medical Centerjhindler@ucla.edujhindler@ucla.edu

…….and working as a consultant with the .and working as a consultant with the Association of Public Health Laboratories Association of Public Health Laboratories with support from CDCwith support from CDC

At the conclusion of this talk, At the conclusion of this talk, you will be able toyou will be able to…………

♦♦ Describe what is currently being done in Describe what is currently being done in PHLsPHLs re: re: antimicrobial susceptibility testing antimicrobial susceptibility testing (AST).(AST).

♦♦ List features, benefits, and costs of commonly used List features, benefits, and costs of commonly used automated and nonautomated and non--automated automated AST systems.AST systems.

♦♦ Discuss the Discuss the role of the PHL role of the PHL in assisting clinical in assisting clinical laboratories with AST problems including emerging laboratories with AST problems including emerging resistance (e.g., CAresistance (e.g., CA--MRSA, VISA, VRSA).MRSA, VISA, VRSA).

♦♦ List List resources availableresources available for performance of AST and for performance of AST and ways in which ways in which PHLs PHLs may help to provide access to these may help to provide access to these resources.resources.

What are PHLs doing What are PHLs doing now re: AST?now re: AST?

AST State PHL AST State PHL Training Needs Survey 2005Training Needs Survey 2005

♦♦36/52 responses (69%)36/52 responses (69%)–– 2 states >1 lab responded2 states >1 lab responded

♦♦29/36 labs do some type of AST29/36 labs do some type of AST–– 16 referral testing16 referral testing–– 10 diagnostic testing10 diagnostic testing–– 25 surveillance25 surveillance

♦♦Desire more training in ASTDesire more training in AST–– 29/36 for surveillance29/36 for surveillance–– 13/36 for diagnostic testing 13/36 for diagnostic testing

Number of State PHLs Performing Number of State PHLs Performing AST on Respective Organisms*AST on Respective Organisms*

OrganismOrganism ForForSurveillanceSurveillance

ForForDiagnosticsDiagnostics

CampylobacterCampylobacter 44 22Salmonella Salmonella spp.spp. 1919 66N. gonorrhoeaeN. gonorrhoeae 1414 77N. meningitidisN. meningitidis 44 11S. aureusS. aureus 2121 1111S. pneumoniaeS. pneumoniae 1212 55Group B streptococciGroup B streptococci 22 66

* of 36 labs that responded

Number of State PHLs UsingNumber of State PHLs UsingTest Methods*Test Methods*

OrganismOrganismDisk DiffDisk Diff EtestEtest

Broth Broth DilutionDilution

CampylobacterCampylobacter 33 33227733

1515101011

--

Salmonella Salmonella spp. spp. 11 1212 33N. gonorrhoeaeN. gonorrhoeae 1010 11N. meningitidisN. meningitidis 11 11S. aureusS. aureus 66 88S. pneumoniaeS. pneumoniae 77 22Group B streptococci Group B streptococci 22 22

* of 36 labs that responded; 1 Vitek (2)

Additional Data from Additional Data from AST State PHL SurveyAST State PHL Survey

♦♦ 9/36 said that their epidemiology section collects 9/36 said that their epidemiology section collects cumulative antibiogram datacumulative antibiogram data from clinical from clinical laboratorieslaboratories

♦♦ Additional AST Methods UtilizationAdditional AST Methods Utilization–– VitekVitek –– 33–– MicroScanMicroScan –– 22–– SensititreSensititre –– 11

♦♦ 23/36 labs use 23/36 labs use EtestEtest for one or more organismsfor one or more organisms

AK

CA

WA

WIMI

VA

PRPR

AL

AZ AR

CO

CTCT

DEDE

GA

IA

FL

IL IN

KS KY

LA

MDMD

NJNJ

MAMA

MONC

ND

NE

NM

NV

NY

OH

OK

OR

PA

SC

SD

TN

TX

UT

VTVT

WV

HAHA

WY

MT

ID

MN

MS

RIRI

NHNH

ME

AST State PHL SurveyAST State PHL SurveySpring 2005Spring 2005

Do Some ASTDo Some AST

Do No ASTDo No AST

No ResponseNo Response

What methods/systems What methods/systems are available for AST?are available for AST?

Who makes the rules for AST and Who makes the rules for AST and reporting of clinical isolates?reporting of clinical isolates?

♦♦The The Clinical and Laboratory Standards InstituteClinical and Laboratory Standards Institute(CLSI, formerly NCCLS) subcommittee on AST(CLSI, formerly NCCLS) subcommittee on AST–– Virtually all labs in USA follow Virtually all labs in USA follow CLSI standardsCLSI standards–– Each lab must Each lab must customizecustomize testing and reporting to meet the testing and reporting to meet the

needs of the facilities they serveneeds of the facilities they serve–– Accrediting agencyAccrediting agency requirements primarily based on CLSI requirements primarily based on CLSI

recommendationsrecommendations

♦♦FDAFDA has rules for manufacturers of AST has rules for manufacturers of AST systems systems

Current CLSI AST StandardsCurrent CLSI AST Standards♦♦M100M100--S16 Tables S16 Tables (2006)*(2006)*

……..to be used with text documents ..to be used with text documents explaining how to perform the testsexplaining how to perform the tests……..

M2M2--A9 Disk DiffusionA9 Disk Diffusion (2006)**(2006)**M7M7--A7 MICA7 MIC (2006)**(2006)**

♦♦M45M45--PP Infrequently Isolated/Fastidious Infrequently Isolated/Fastidious Bacteria (Bacteria (NEW,NEW, 2005)2005)

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

CLSI M100CLSI M100--S16 Table 1S16 Table 1Drugs to Test/ReportDrugs to Test/Report

What drugs should we test / report?What drugs should we test / report?

How should we interpret results?How should we interpret results?

CLSI M100CLSI M100--S16 Table 2CS16 Table 2CInterpretive Criteria Interpretive Criteria

(Breakpoints)(Breakpoints)

CLSI M100CLSI M100--S16 Table 3S16 Table 3QC Strain RangesQC Strain Ranges

How can we ensure accurate results?How can we ensure accurate results?

Clinical lab can use a CLSI reference Clinical lab can use a CLSI reference methodmethod……....

Disk diffusion Disk diffusion (Kirby Bauer)(Kirby Bauer)

Drug A B C DDrug A B C D

- +

6432168421

>64

0.5

>64

Broth microdilution MICBroth microdilution MIC

Vitek 2Vitek 2

SensititreSensititre

PhoenixPhoenix

EtestEtest

BIOMICBIOMIC

MicroScanMicroScan

……or an FDAor an FDA--cleared commercial systemcleared commercial system

Comparison of AST SystemsComparison of AST SystemsCLSI CLSI

Disk DiffDisk DiffBIOBIOMICMIC

EtestEtest MicroMicroScanScan

PhoenixPhoenix SensititreSensititre VitekVitek

Identification of Identification of bacteriabacteria

-- XX -- XX XX XX XX

XX

XX

XX

--**$7 $7 -- 1010

AST fastidiousAST fastidiousbacteriabacteria

XX XX XX XX XX XX

Automated readAutomated read -- XX -- XX XX XX

Rapid result Rapid result optionoption

-- -- -- XX XX XX

Manual read Manual read optionoption

XX --** XX XX --** XX

Cost/panel of 10 Cost/panel of 10 drugs (approx)drugs (approx)

$2$2 $2$2 $22$22 $7 $7 -- 1010 $7 $7 -- 1010 $7 $7 -- 1010

--*, significant capital equipment cost*, significant capital equipment cost

Why would a PHL do AST?Why would a PHL do AST?–– Emerging antimicrobial resistance Emerging antimicrobial resistance (AR)(AR) is a is a

PH concernPH concern–– Clinical labs sometimes need help with Clinical labs sometimes need help with

detection of emerging resistancedetection of emerging resistance

Why would a PHL Why would a PHL NOTNOT do AST?do AST?–– Limited resourcesLimited resources–– Clinical labs have expertise in ASTClinical labs have expertise in AST

““PHLs: Potential Leaders in the Fight PHLs: Potential Leaders in the Fight Against Antimicrobial ResistanceAgainst Antimicrobial Resistance””

(APHL Minute, May(APHL Minute, May--June, 2006)June, 2006)

Approaches to AR & AST in a Approaches to AR & AST in a PHLPHL……♦♦Test isolates Test isolates ““referredreferred”” from clinical labs from clinical labs

((““referralreferral”” isolates)isolates)–– To To verifyverify noteworthy results from clinical labnoteworthy results from clinical lab–– To To test supplemental drugstest supplemental drugs on highly resistant bacteriaon highly resistant bacteria–– To To do tests not donedo tests not done in smaller clinical lab [e.g., extendedin smaller clinical lab [e.g., extended--

spectrum spectrum ββ--lactamase (ESBL) confirmatory test; lactamase (ESBL) confirmatory test; mecmecA, A, etc.]etc.]

–– Clinical labs on Clinical labs on ““front linefront line””♦♦Surveillance Surveillance for ARfor AR♦♦Test isolates from Test isolates from diagnostic specimensdiagnostic specimens♦♦QA QA of AR detection / reportingof AR detection / reporting

CLSI M100CLSI M100--S16 (2006) Table 8 (M7)S16 (2006) Table 8 (M7)What isolates should be What isolates should be ““verifiedverified””

and possibly referred?and possibly referred?

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

Organism or Organism or GroupGroup

Category ICategory IVerify at all labsVerify at all labs

Category IICategory IIVerify Verify –– institution institution

specificspecificStaphylococcus Staphylococcus aureusaureus

linezolid linezolid –– NSNSvancomycin vancomycin –– I or RI or R

oxacillin oxacillin –– RR

Streptococcus Streptococcus pneumoniaepneumoniae

vancomycin vancomycin –– NSNS penicillin penicillin –– RR

CLSI M100CLSI M100--S16 Tables 4 (M2) and 8 (M7)S16 Tables 4 (M2) and 8 (M7)NS, not susceptibleNS, not susceptible

What is the basis of the What is the basis of the ““suggestions for verificationsuggestions for verification”” list?list?

♦♦List includes results that..List includes results that..–– have never been documented*have never been documented*–– have rarely been documentedhave rarely been documented–– can easily result from technical errorscan easily result from technical errors

*critical PH importance!*critical PH importance!

AcceptablePrimary Test Methods

Include:

Important Footnotes1 Laboratories using automated MIC methods that have not been validated for VRSA detection should add a commercial VA agar screen plate (6 µg/ml).2 Disk diffusion will not differentiate VISA (MICs 4-8) from susceptible strains (MICs 0.5-2). VA screen plate will not reliably detect strains for which MIC=4. 3 If concerned about a result based on a patient’s history, send to a reference lab for MIC testing.4 Validated methods: reference broth microdilution, agar dilution, Etest® (0.5 McFarland inoculum, Mueller-Hinton agar), MicroScan® overnight and Synergies plus™; BD Phoenix™ system. For other automated methods, check with the manufacturer about FDA-clearance to detect MICs =4 (i.e., VISA/VRSA).5 Report to CDC by email: SEARCH@cdc.gov

Algorithm Revised:March 31, 2006

More VISA/VRSA info: http://www.cdc.gov/ncidod/dhqp/ar_visavrsa.html

Disk diffusion plus VA screen plate2(BHIA with 6 µg/ml of VA)

VA MIC 15 mmAND NO growth on

VA screen plate

CONFIRM isolate ID

RETEST using a validated MIC method4

SEND to reference laboratory for confirmation

Clinical and Laboratory Standards Institute S. aureus/Vancomycin Breakpoints

(M100-S16; Jan. 2006)Susceptible: ¡Â2 µg/ml (VSSA)Intermediate: 4-8 µg/ml (VISA)Resistant: ¡Ã16 µg/ml (VRSA)

Algorithm for Testing Algorithm for Testing S. aureusS. aureus with Vancomycin (VA)with Vancomycin (VA)

Streptococcus pneumoniae Streptococcus pneumoniae VancomycinVancomycin

SuscSusc IntInt ResRes

DD (mm)DD (mm) ≥≥1717 -- --

MIC MIC ((µµg/ml)g/ml) ≤≤1 1 -- --

*CLSI states: investigate non- susceptible (NS) result..Repeat identification and AST..Repeat identification and AST..Save isolate..Save isolate..Send to reference lab..Send to reference lab

Where do Clinical Labs need help Where do Clinical Labs need help with with ““referralreferral”” isolates?isolates?

ResistanceResistance Clinical Labs need help to rapidly and Clinical Labs need help to rapidly and accuratelyaccurately……..

MRSAMRSA Characterize CACharacterize CA--MRSA vs. HAMRSA vs. HA--MRSA MRSA (?outbreaks) (?outbreaks) –– rapid result not always rapid result not always essentialessential

VISA, VRSAVISA, VRSA VerifyVerify

VREVRE Test broad spectrum drugsTest broad spectrum drugs

DRSPDRSP Test certain drugs by MIC (systemic isolates)Test certain drugs by MIC (systemic isolates)

Where do Clinical Labs need help Where do Clinical Labs need help with with ““referralreferral”” isolates? (conisolates? (con’’t)?t)?

ResistanceResistance Clinical Labs need help to rapidly and Clinical Labs need help to rapidly and accuratelyaccurately……..

ESBLESBL Perform confirmatory test (smaller labs often Perform confirmatory test (smaller labs often dondon’’t do confirmatory test)t do confirmatory test)

MultidrugMultidrug--R R GNRGNR

Test broad spectrum drugsTest broad spectrum drugs

OtherOther Verify unusual results (e.g., vancomycinVerify unusual results (e.g., vancomycin--NS NS S. S. pneumoniaepneumoniae; imipenem; imipenem--R R Klebsiella Klebsiella sppspp..))

AST of Referral IsolatesAST of Referral Isolates

♦♦Preferred AST method = Preferred AST method = CLSI broth CLSI broth microdilution MIC reference methodmicrodilution MIC reference method ……oror

♦♦Method proven reliable by CDCMethod proven reliable by CDC♦♦EtestEtest sometimes an optionsometimes an option♦♦MustMust be aware of be aware of pitfalls of certain AST pitfalls of certain AST

methodsmethods to reliably resolve equivocal to reliably resolve equivocal results or identify emerging resistanceresults or identify emerging resistance

♦♦Often requires Often requires expertiseexpertise

PHL Surveillance for ARPHL Surveillance for AR♦♦ Compile AST dataCompile AST data to answer specific question, e.g.,to answer specific question, e.g.,

–– How many MRSA from EMC patients are susceptible to How many MRSA from EMC patients are susceptible to trimethoprimtrimethoprim--sulfamethoxazole? clindamycin?sulfamethoxazole? clindamycin?

♦♦ Collect isolatesCollect isolates from the community and test from the community and test ♦♦ Alternative, Alternative, collect datacollect data from hospital laboratoriesfrom hospital laboratories♦♦ Must consider Must consider all factors that might impact dataall factors that might impact data, ,

e.g.,e.g.,–– Isolates or drugs selectively tested?Isolates or drugs selectively tested?–– Inclusion / exclusion of duplicate isolates on a patient?Inclusion / exclusion of duplicate isolates on a patient?–– Hospitalization history?Hospitalization history?–– Clonal isolates from a given facility?Clonal isolates from a given facility?

CLSI M39CLSI M39--A2 GuidelineA2 Guideline

““Analysis and Presentation of Analysis and Presentation of Cumulative Antimicrobial Cumulative Antimicrobial Susceptibility Test DataSusceptibility Test Data””

Purpose: aid in preparation of Purpose: aid in preparation of cumulative antibiogram reports to cumulative antibiogram reports to guide empiric therapy of initial guide empiric therapy of initial infectionsinfections..

Relative importance of requirements of AST Relative importance of requirements of AST system depending on purpose of testing system depending on purpose of testing (Hindler opinion!)(Hindler opinion!)……....

RequirementRequirement ReferralReferral SurveillanceSurveillance

AccuracyAccuracy 55

55

55

33

55

44

Turn around timeTurn around time 11

MIC result MIC result (vs. S I R only)(vs. S I R only)

3 (depends on 3 (depends on question posed)question posed)

CostCost 55

AST expertiseAST expertise 44

Scale = 1 (least important) to 5 (extremely important)Scale = 1 (least important) to 5 (extremely important)

What resources (in addition to What resources (in addition to CLSI standards) are available for CLSI standards) are available for

keeping appraised of new keeping appraised of new developments in AST?developments in AST?

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

NLTNNLTN

To view Jan 2006 teleconference To view Jan 2006 teleconference --details of M100details of M100--S16S16

CDC AST CDCDC AST CD--ROMROM♦♦ Modes of action / Modes of action /

mechanisms of resistancemechanisms of resistance♦♦ MethodsMethods♦♦ GramGram--positive bacteriapositive bacteria♦♦ GramGram--negative bacterianegative bacteria

If your lab does NOT have a copy of this, please email jhindler@ucla.edu.

www.phppo.cdc.gov/dls/master/default.asp

American Society for Microbiology Online

Features!

http://www.asm.org/division/c/greatfeatures.htmhttp://www.asm.org/division/c/greatfeatures.htm

http://http://www.cdc.gov/ncidod/dhqp/pdf/ar/CAMRSA_ExpMtgStrategies.pdfwww.cdc.gov/ncidod/dhqp/pdf/ar/CAMRSA_ExpMtgStrategies.pdf

Summary of ExpectationsSummary of Expectations……....

PHLPHL expects Clin Lab to expects Clin Lab to provide:provide:

•• Isolates w/ unusual Isolates w/ unusual ““RR”” (e.g., (e.g., VRSA)VRSA)

…….maybe.maybe•• Cumulative antibiogram dataCumulative antibiogram data

Clin Lab expects Clin Lab expects PHLPHL to to provide:provide:

•• Strategy for verification of Strategy for verification of unusual isolates unusual isolates

•• ““NewNew”” Technical information Technical information from CDC / APHL / Othersfrom CDC / APHL / Others

•• Notice of training eventsNotice of training events

……maybemaybe•• Regional antibiogram dataRegional antibiogram data•• CLSI AST standardsCLSI AST standards

How can How can PHLsPHLs help Clinical Labs help Clinical Labs nownow……for minimal $$$$?for minimal $$$$?

♦♦ Inform them of Inform them of resources resources for verification of for verification of ““referralreferral”” isolatesisolates–– PHL? (test in house or send to CDC)PHL? (test in house or send to CDC)–– Local university lab or reference lab Local university lab or reference lab –– partner???partner???

♦♦ Inform them which isolates with Inform them which isolates with specific Rspecific Rshould be reported to PH departmentshould be reported to PH department

♦♦ Inform them of Inform them of anyany emergingemerging R bug R bug problemproblem in their state rapidly!in their state rapidly!–– e.g., ceftriaxonee.g., ceftriaxone--R R SalmonellaSalmonella spp.spp.

How can How can PHLsPHLs help Clinical Labs help Clinical Labs nownow……for minimal $$$$ (confor minimal $$$$ (con’’t)?t)?

♦♦Inform them of what the state PHL (or Inform them of what the state PHL (or Epi)Epi) is doing re: ARis doing re: AR

♦♦Provide education on new AR and Provide education on new AR and AST issues AST issues --–– Many materials provided by National Many materials provided by National

Laboratory Training Network (NLTN)Laboratory Training Network (NLTN)–– CLSI standards for ASTCLSI standards for AST

Meeting Antimicrobial Resistance Meeting Antimicrobial Resistance ChallengesChallenges

Clin Labs

NLTNAPHL

PHLs (& Epi)State Training Coordinators

NLTN Ongoing Efforts re: ASTNLTN Ongoing Efforts re: AST

♦♦PHLPHL--directed directed webcastswebcasts on ASTon AST–– March 2006 (AST systems)March 2006 (AST systems)–– May 2006 (VISA, VRSA, MRSA)May 2006 (VISA, VRSA, MRSA)–– More planned!More planned!

♦♦Programs for clinical labsPrograms for clinical labs♦♦Assist individual PHLsAssist individual PHLs with specific with specific

needs needs

““I would ask PHLs to look for ways that I would ask PHLs to look for ways that they can become more integrated with they can become more integrated with clinical labs and develop strategies for clinical labs and develop strategies for

ensuring accurate AST. Good ensuring accurate AST. Good surveillance data is the lynchpin for all surveillance data is the lynchpin for all

our work.our work.””

Todd Weber, MD; Todd Weber, MD; Director of CDCs Office or AR Director of CDCs Office or AR (APHL Minute, May(APHL Minute, May--June, 2006)June, 2006)

Contemporary Issues in Antimicrobial Susceptibility Testing (AST) for Public Health Laboratories!At the conclusion of this talk, you will be able to……What are PHLs doing now re: AST?AST State PHL �Training Needs Survey 2005Number of State PHLs Performing AST on Respective Organisms*Number of State PHLs Using�Test Methods*Additional Data from �AST State PHL SurveyWhat methods/systems are available for AST?Who makes the rules for AST and reporting of clinical isolates?Current CLSI AST StandardsClinical lab can use a CLSI reference method…..Comparison of AST SystemsApproaches to AR & AST in a �PHL…Excerpt from:�“Suggestions for Verification of AST Results and Confirmation of Organism Identification”�What is the basis of the “suggestions for verification” list?Streptococcus pneumoniae �VancomycinWhere do Clinical Labs need help with “referral” isolates? Where do Clinical Labs need help with “referral” isolates? (con’t)? AST of Referral IsolatesPHL Surveillance for ARCLSI M39-A2 GuidelineRelative importance of requirements of AST system depending on purpose of testing (Hindler opinion!)…..What resources (in addition to CLSI standards) are available for keeping appraised of new developments in AST?CDC AST CD-ROMSummary of Expectations…..How can PHLs help Clinical Labs now…for minimal $$$$?How can PHLs help Clinical Labs now…for minimal $$$$ (con’t)?Meeting Antimicrobial Resistance Challenges�NLTN Ongoing Efforts re: AST“I would ask PHLs to look for ways that they can become more integrated with clinical labs and develop strategies for ensuring