Medical Microbiology

ThePrinciplesofAntibioticTherapy 197

MechanismsofAction.....................................

Table3. 5 providesaconcisesummaryofthemolecularmechanismsofaction

ofthemostimportantgroupsofanti-infectiveagents.

EfficacyofSelectedAntI-InfectiveAgents

Number of viable cells (log

10

)

Time (hours)

Co

ntr

ol

Betalactams

Amino-

glycosides

Tetracyclines

Betalactams,

aminoglycosi-

des

Persisters

Sulfonamides

Fig.3. 30 Thearrowsindicateadditionofsubstancesinthedifferentphasesof

thenormalgrowthcurve(seeFig.3. 16 ).Betalactamsarebactericidalonlyduring

thebacterialcelldivisionphase,whereasaminoglycosidesshowthisactivityinall

growthphases.Sulfonamidesarealwaysbacteriostatic,tetracyclinesaremainly

bacteriostatic.Somecellsineveryculture(so-calledpersisters)arephenotypically

(butnotgenotypically)resistanttothebactericidaleffectsofanti-infectiveagents.

3

Kayser, Medical Microbiology © 2005 Thieme