Cole,1984;Reybrouck, 1991;Bloomfieldand Looney,1992;Bloomfieldet al.,
1994,1995;Langsrudand Sundheim, 1998;Tilt and Hamilton,1999;Kampfand
Ostermeyer, 2002;Borgmann-Strahsen,2003;Kneale, 2003). The variabilityin
resultson the antimicrobialactivity of a givenagentas reportedin the literature
oftenresidesin the differencesin protocolsused,sometests being less stringent
thanothers (Kampfet al., 2003;Marchetiet al., 2003;Messageret al., 2004b),
but also the non-respectof test preparation(notably inoculum)and conditions.
Indeedtherehavebeenseveralreportsof commercialdisinfectants failinga basic
suspensiontest (Jacquetand Reynaud,1994;Tayloret al., 1999).A drivetowards
the standardisation of antimicrobial tests, such as with European testing
protocols, provides a much-neededimprovementin this field. However, the
differenttest requirementsand conditions(Table 38.9)needto be clearly thought,
definedand respected.Preparationof the inoculais of paramount importance
(Bloomfieldet al., 1995;Johnstonet al., 2000).Standardisation of the inoculum,
at leastin the Europeansuspension test, has improved reproducibilityin results.
The reproducibilityof antimicrobialsurfacetests mightremain an issuewhere
the inoculumis difficult to standardise.Overall, antimicrobialefficacytests can
be complex(Table 38.9)and it is impossibleto standardise all the equipment,
glassware and consumables,and thus results will be subjectto variability from
one laboratoryto the next. In addition,the operatorwill undoubtedly add
variability in the test (Bloomfieldet al., 1994).
Reproducibilityset aside,limitationsof antimicrobialtest protocols probably
are concernedwithtwo levelsof testing:practicalandin situtest. The ideaof
practicaltestsis to simulate conditionsin the field.The rigidityof some testing
protocols doesnot allowmuch flexibility,althoughwith antimicrobialtests
recommendedby CEN/TC 216,additionaltemperature, contacttimeand micro-
organismscan be chosento reflect conditionsin practice moreappropriately.
Stillthe determinationof mycobactericidal,sporicidal or virucidal activity
requires specifictesting protocols. Testing for viruses is particularlya problem,
notablywiththe question aboutthe appropriatetest virusto be used.Viruses
differtremendously in structureand sensitivityto biocides and a multitude of
testingprotocols exist(Maillard,2004),althoughsome standardisationwill be
introduced (Holah, 2003).
Testsin locoare costlyand difficultto standardise since parameters cannotbe
controlled accurately in the field.Thesetestsremain poorlyreproducibleand
theiroutcomes may be contentious. It is difficult to imagine improvementsin the
in situtestsin the nearfuture,althoughthesetests wouldprovide key informa-
tion on the antimicrobialefficacy of a disinfectant/sanitiserto the manufacturers
and end users.
38.6 Future trends
Suspensionand surface tests use microorganismsthathavebeen grown in a
planktonicsystem.Althoughthis mightbe appropriatefor preliminarytests,the
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