ASTM_E_2315_-_03_2008.pdf

Designation:E231503(Reapproved 2008)Standard Guide forAssessment of Antimicrobial Activity Using a Time-KillProcedure1This standard is issued under the fixed designation E2315;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This guide covers examples of a basic method tomeasure the changes of a population of aerobic microorgan-isms within a specified sampling time when tested againstantimicrobial test materials in vitro.Several options for organ-ism selection and growth,inoculum preparation,samplingtimes and temperatures are provided.When the basic techniqueis performed as a specific test method it is critical whenevaluating the results to ensure that such variables have beenstandardized.Antimicrobial activity of specific materials,asmeasured by this technique,may vary significantly dependingon variables selected.It is important to understand the limita-tions of in vitro tests,especially comparisons of results fromtests performed under different circumstances.As an example,test results of microorganisms requiring growth supplements,or special incubation conditions,may not be directly compa-rable to more robust organisms under the conditions of a singleprocedure.1.2 Knowledge of microbiological techniques is requiredfor this test.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 This standard may involve hazardous materials,opera-tions and equipment.This standard does not purport to addressall of the safety concerns,if any,associated with its use.It isthe responsibility of the user of this standard to establishappropriate safety and health practices and determine theapplicability of regulatory requirements prior to use.2.Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE1054 Test Methods for Evaluation of Inactivators of Anti-microbial Agents3.Terminology3.1 Definitions:3.1.1 inoculum suspension,nthe initial suspension of testorganism used to inoculate the test material This may also beknown as the organism inoculum(see 8.2).3.1.2 microbial population,nthe microbial count(cfu/mL)in the final volume of test material(see 9.4).This may alsobe known as the“initial population”or“numbers control.”3.1.3 neutralization,na process which results in the inac-tivation or quenching of the antimicrobial activity of a testmaterial.This may be achieved through dilution of the testmaterial(s)or with the use of chemical agents,calledneutralizers,to reduce or quench the antimicrobial activity.3.1.4 neutralizer,na procedure or chemical agent used toinactivate,neutralize,or quench the microbiocidal properties ofan antimicrobial agent.3.1.5 total test volume,nthe volume of test material plusthe volume of inoculum suspension.4.Summary of a Basic Test Method4.1 The test material or a dilution of the test material isbrought into contact with a known population of microorgan-isms for a specified period of time at a specified temperature.The activity of the test material is quenched at specifiedsampling intervals(for example,30 s,60 s,or any rangecovering several minutes or hours)with an appropriate neu-tralization technique.The test material is neutralized at thesampling time and the surviving microorganisms enumerated.The percent or log10reduction,or both,from either an initialmicrobial population,or test blank is calculated.5.Significance and Use5.1 This procedure may be used to assess the in vitroreduction of a microbial population of test organisms afterexposure to a test material.6.Apparatus6.1 Sterile Vials or Test Tubes,or equivalent.1This guide is under the jurisdiction of ASTM Committee E35 on Pesticides,Antimicrobials,and Alternative Control Agentsand is the direct responsibility ofSubcommittee E35.15 on Antimicrobial Agents.Current edition approved April 1,2008.Published May 2008.Originallyapproved in 2003.Last previous edition approved in 2003 as E2315 03.DOI:10.1520/E2315-03R08.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.2 Timer(Stop-clock),one that displays minutes and sec-onds.6.3 Shaking Water Bath or Controlled TemperatureChamber,or equivalent capable of maintaining test system atthe specified exposure temperature 6 2C.6.4 Colony Counter,any of several manual or automatedtypes may be used.6.5 Incubator,any incubator capable of maintaining a speci-fied temperature 62C may be used.6.6 Sterilizer,any suitable steam sterilizer capable of pro-ducing the conditions of ster