Medical Microbiology

290 4 BacteriaasHumanPathogens

plagueepidemicsinhumansresultedfromthesesametransmissionpath-

ways.Therarehumaninfectionsseentodayresultfromcontactwithrodents

thatareinfectedwithorhavediedofplague.Thepathogenbreachestheskin

throughdermalinjuries.Fromsuchalocation,thebacteriareachregional

lymphnodesinwhichtheyproliferate.Twotofivedaysafterinfection,hem-

orrhagicallyaltered,blue,andswollenlymphnodes(buboes)areobserved.

Over 90 %ofpestisinfectionsshowthe“bubonicplague”course.In 50 – 90 %of

untreatedcases,theorganismsbreakoutintothebloodstreamtocauseaclin-

icalsepsis,inthecourseofwhichtheymayinvademanydifferentorgans.

Disseminationintothepulmonarycirculationresultsinsecondarypulmon-

aryplaguewithbloody,bacteria-rich,highlyinfectioussputum.Contactwith

suchpatientscanresultinprimarypulmonaryplagueinfectionsduetodirect,

aerogenictransmission.Leftuntreated,thisformofplagueislethalinnearly

100 %ofcases.

Diagnosis.Thepathogenmustbeidentifiedinbubopunctate,sputum,or

bloodbymeansofmicroscopyandculturing.

Therapy.Inadditiontosymptomatictreatment,antibioticsaretheprimary

method(streptomycin,tetracyclines,inthecaseofmeningitis,chloramphe-

nicol).Incisionofthebuboesiscontraindicated.

Epidemiologyandprevention.Plaguestilloccursendemicallyinwildro-

dentsoverlargeareasofAsia,Africa,SouthAmerica,andNorthAmerica.

Humanplagueinfectionshavebeenreducedtosporadicinstances.The

sourcesofinfectionaremainlydiseasedrodents.Transmissionofthedis-

easeismainlyviadirectcontactwithsuchanimals.

Preventioninvolvesexposureprophylacticmeasures.Personswithmani-

festdisease,inparticularthepulmonaryform,mustbeisolated.Contactper-

sonsmustbequarantinedforsixdays(=incubationperiod).Casesofplague

infectionmustbereportedtohealthauthorities.

YersiniaenterocoliticaandYersinia

pseudotuberculosis

Occurrenceandsignificance.Y.enterocoliticaandY.pseudotuberculosiscause

generalizedinfectionsindomesticandwildanimals,especiallyrodents.The

pathogenscanbetransmittedfromanimalstohumans.Y.enterocoliticais

responsibleforabout 1 %ofacuteenteritiscasesinEurope.Y.pseudotuber-

culosisisinsignificantintermsofhumanpathology.

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Kayser, Medical Microbiology © 2005 Thieme