Scanning Electron Microscopy ofBacteria Adherent toIntravascular Catheters

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catheters demonstrated multiple linear surface irregularities. Scanning electron microscopy ofinfected patient catheters showeda diffuse material covering theentire surface andthepresenceofbacteria whichappeared anchored tothatsurface byseveral different means. Theseincluded a slime layer, foot processes,andlodgement in surface irregularities. Scanning electron microscopy ofinvitro specimens demonstrated no background surface coating, butitdidshowattachment ofcocci tothesurface bythesame mechanisms asdescribed forclinical specimens. Theseobservations ofsimilar means ofattachment inclinical andinvitro specimens suggest that intrinsic catheter surface properties, bacterial surface features, andperhaps coating withhostsubstances may allplaya roleinbacterial attachment tointravascular catheters. Moresophisticated analysis ofthese interactions may clarify mechanisms ofpathogenesis. Infections associated withtheuseofintravascular devices canbea serious complication ofparenteral therapy in hospitalized patients. Intravenous catheter-associated infections havebeenreported toberelated tolocal skinconditions, catheter placement techniques, andtheduration of catheter useatonesite (7,15). However, theinitiating event andevolution ofthemechanisms leading toclinical infection haveyettobeelucidated. Mostauthorities nowsuspect thatorganisms fromeither exogenous sources (such asthehandsofpersonnel) or microflora indigenous topatients invade viathecatheter insertion woundandmigrate along theexternal catheter surface, eventually colonizing theintravascular catheter segment (13, 14). Bacteremia frominfections atdistant sites mayalsoseedthecatheter surface (17). Ineither event, the encasement offibrin, plasma proteins, platelets, andother undefined around theexternal catheter surface mayprovide a nidusconducive tobacterial implantation. Thekinetics ofthiscatheter-organism interaction arenot clear, andthecatheter persehasbeenpreviously thought to beonly aninert, innocent bystander inthis process. However,recent studies fromourlaboratory indicate thatdifferent catheter materials havevarying affinities forbacterial adherence(20). Studies byLoccietal.(12) andPeters etal.(18) have addressed themorphology ofbacterial adherence tocatheter lumenandexternal surfaces invitro andinvivobyusing scanning electron microscopy (SEM). Intheir studies, itwas notedthat there wereabundant amorphous deposited substances surrounding bacteria adherent tothesesurfaces. Christensen etal.also observed thatslime-producing strains ofcoagulase-negative staphylococci demonstrated increased adherence toplastic surfaces ascompared withnon-slime

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