Triclosan and hexachloropheneare the mostwidelyused(McDonnelland Russell,
1999). Triclosan,a derivativeof diphenylether,is knownas an ingredientin some
medicatedsoaps and hand-cleansinggels and toothpastes,and is effectiveagainst
staphylococci(Hugoand Russell, 1999). It is currentlyappliedas antimicrobial
layerin packagingmaterial(Vermeirenet al., 2002;Chunget al., 2003)and
conveyerbelts (QuantexLaboratories, 2001 ; Stekelenburgand Hartog,2002).
Unfortunately,dependingon the impurityof the startingmaterial,Triclosancan
containconcentrationsof dioxinand dibenzofurans, bothsubstanceshighlytoxic
to humans(QuantexLaboratories,2001).Therefore,it is of great importancethat
the originand way of productionare known priorto applicationin foodproduction
areas. Hexachlorophenehas beenusedin soaps as well;in 1972it was restrictedin
use by the US Foodand DrugAdministration(FDA)to levelsless than0.1%.
Nowadays,applicationas a surgicalscrubber in caseof certaininfectionsis
permitted(SpectrumLaboratories).
Modeof action
The exactmodeof actionis unknown so far but it is suggested that Triclosan
affects the cytoplasmic membrane. However, current research shows that
Triclosaninhibits one specificenzymeof the fattyacid synthesisofE. coli. This
increases the risk of resistance againstTriclosan as one mutationof a genecan
result in a decreased efficacyof the disinfectant(Sixma, 2001).Hexachloro-
phene affects bacteria by inducing leakage, causing protoplast lysis and
inhibitingrespiration.
4.2.7 Biguanides
The groupof biguanides is representedby chlorhexidine,alexidineand poly-
mericbiguanides (McDonnelland Russell, 1999;Hugoand Russell, 1999).
Chlorhexidine is probably the most widelyappliedbiocide in hand-washingand
oralproducts suchas mouthwash,mouthsprayand throat-lozenges(Sixma,
2001) and is bacteriostatic at concentrations of 0.0001mg lˇ^1 as well as
bactericidalat concentrationsof 0.002mg lˇ^1 (Russell, 1991).Chlorhexidinehas
a broadspectrumof activity and is pH-dependent(higherefficacyat alkaline
ratherthanacidpH); its efficacyis greatly reducedby the presenceof organic
matter. Highconcentrationsof chlorhexidinecausecoagulation of intracellular
constituents(Russell, 1990; McDonnell and Russell,1999).Chlorhexidineis
onlysporicidal at elevated temperatures (>0.005mg lˇ^1 at 70 ÎC) and is in
general moresporostatic;it has littleeffecton the germinationof the sporebut
doesnot prevent the outgrowth of the spore(Russell, 1991;Gormanet al.,
1987).Alexidine and the polymericbiguanidesare usedonlyon a small scale.
The polymeric biguanidesare usedin particular by the foodindustry and also for
the disinfection of swimming pools. An example is poly(hexamethylene
biguanide)hydrochloride (PHMB) which is the main active ingredient of
Vantocil,whichis widelyusedin the foodindustry, hospitals,nursinghomes
and consumerhouseholds(Avecia,2004).
76 Handbookof hygiene controlin the foodindustry