humanpathogen,whichmakesits routineuse for disinfectiontesting difficult
and expensive. In addition,thereis a markeddifferencein biocidesusceptibility
between species, which leadsto the question as to which mycobacterial
surrogate can be usedin antimicrobialefficacytesting.M. bovisis recommended
in the EPAand AOAC(confirmation)tests, M. smegmatis in the AOAC
(screening) and AFNOR tests,andM. tuberculosisandM. terraein the DGHM.
However,M. smegmatiswas reported to be more sensitive thanM. tuberculosis
and thusis not recommendedas a test surrogate.M. avium-intracellularehas
beenfoundto be generally more resistantto biocides thanM. tuberculosisand
M. terrae. Nevertheless,M. terraeappears to meet the criteriafor an appropriate
surrogate for M tuberculosis (Griffiths et al., 1998). Mycobactericidal
suspensionand carriertests havebeenpublished (Ascenziet al., 1987;AOAC,
1990;Ascenzi, 1991), althoughconcerns have beenexpressedtowards the
reproducibilityof mycobactericidalsuspensiontests(Robisonet al., 1996).
Disinfectants/sanitisers are usually not required to show antimicrobial
activity againstbacterialspores, except in specific circumstances,wherethe
risk of contamination/infectionby a sporulatedspecieshas beenestablished.
Specific sporicidaltest protocols havebeenpublished and the maindifference
withthe test protocols described aboveis in the preparation of the spore
inoculum; vegetativecells haveto be removedand it is important that the spore
structureand vitalityare not damagedduring the preparation of the inoculum
(Tanimotoet al., 1996).Bacillus subtilis,B. cereusandClostridiumsporogenes
havebeenusedas test microorganisms.Several sporicidal testsprotocolshave
beenpublished (Cremieuxet al., 2001).
Thissection wouldnot be complete without mentioning prions,the agents
responsible for transmissibledegenerative encephalopathies (TDEs). As for
spores,disinfectants/sanitisersare not required to showactivityagainstprions,
whichare probablythe most resistant entities. Theyare highlyresistantto
biocides and often completeeliminationof the agentsinvolvedrasticmeasures
suchas the use of highlycorrosive and toxicbiocidesor a combination of heat
and chemical inactivation (Taylor, 2004). Decontamination studies are
particularly difficult to set up sincethe prion`inoculum'is oftendifficult to
standardise and is closely associatedwithhost tissues,whichmightconfersome
levelof protection. In addition,bioassays needto be usedto detect reliably TDE
infectivity (Tayloret al., 2000).As a result,thereis somevariability in prion
inactivation resultsin the literature,because of the numberof differenttest
protocols used.Nevertheless, it is recommended to use harsh conditionsto
simulate the worst casescenario (Taylor,2004).
38.5 Testlimitationsand scopefor improvement
One can arguethat thereis alwaysscopefor improvement,particularlywiththe
reproducibilityof theseprotocols. Reproducibility,robustnessand limitationsof
testingregimenshavebeenreported in the literature(Groschel, 1983;Rutalaand
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