Medical Microbiology

40 1 GeneralAspectsofMedicalMicrobiology

disintegratesintoHCland^1 / 2 O 2 andthusactsasapowerfuloxidant.Chlorine

isusedtodisinfectdrinkingwaterandswimming-poolwater(upto0.5mg/l).

Calciumhypochlorite(chlorinatedlime)canbeusedinnonspecificdisinfec-

tionofexcretions.Chloraminesareorganicchlorinecompoundsthatsplitoff

chlorineinaqueoussolutions.Theyareusedincleaningandwashingpro-

ductsandtodisinfectexcretions.

Iodinehasqualitiessimilartothoseofchlorine.Themostimportantiodine

preparationsarethesolutionsofiodineandpotassiumiodideinalcohol(tinc-

tureofiodine)usedtodisinfectskinandsmallwounds.Iodophoresarecom-

plexesofiodineandsurfactants(e.g.,polyvinylpyrrolidone).Whileiodo-

phoresarelessirritanttotheskinthanpureiodine,theyarealsolesseffective

asgermicides.

Oxidants.Thisgroupincludesozone,hydrogenperoxide,potassiumperman-

ganate,andperaceticacid.Theirrelevantchemicalactivityisbasedonthe

splittingoffofoxygen.Mostareusedasmildantisepticstodisinfectmucosa,

skin,orwounds.

Surfactants.Thesesubstances(alsoknownassurface-activeagents,tensides,

ordetergents)includeanionic,cationic,amphoteric,andnonionicdetergent

compounds,ofwhichthecationicandamphoterictypesarethemosteffec-

tive(Fig. 1. 8 ).

Thebactericidaleffectofthesesubstancesisonlymoderate.Theyhaveno

effectatallontuberculosisbacteria(withtheexceptionofamphotensides),

spores,ornonencapsulatedviruses.TheirefficacyisgoodagainstGram-pos-

itivebacteria,butlesssoagainstGram-negativerods.Theiradvantagesin-

cludelowtoxicitylevels,lackofodor,goodskintolerance,andacleaningef-

fect.

PracticalDisinfection

Theobjectiveofsurgicalhanddisinfectionistorenderasurgeon’shandsas

freeoforganismsaspossible.Theprocedureisappliedafterwashingthe

handsthoroughly.Alcoholicpreparationsarebestsuitedforthispurpose,

althoughtheyarenotsporicidalandhaveonlyabriefdurationofaction.

SurfactantDisinfectants

b

R N

H

CH 2 COOH

R^2 R^3

R^1 R^4

N

+

X–

a

Fig. 1. 8 Quaternaryammoniumcom-

pounds(a)andamphotericsubstances

(b)disrupttheintegrityandfunction

ofmicrobialmembranes.

1

Kayser, Medical Microbiology © 2005 Thieme