Yersinia Pestis

Gram neg rodsfacultatively anerobic

-primarily an animal pathogen with occasional, accidental transmission to human-causes bubonic and pneumonic plague-referred to as "black death"-organism carried by fleas

-fleas are carried by wild prairie dogs, rabbits, squirrels, rats, domestic cats,-human infection results when the human touches a dead animal and flea jumps on human-leads to bubonic plague-usually 10 cases/year in US

-starts when an urban rat becomes infected with fleas from a wild animal-urban rat population soar in cities with crowding and poor hygienerat becomes infected with fleasfleas move rat to ratrat gets sick and diesfleas need a new hostjump from dead rat to humanflea bites humanregurgitates Y pestis into woundmoves to lymph nodes to replicateleads to septicemia

1. LPS2. capsular glycoprotein antigen F13. Icr gene product (low calcium response)4. Yersinia outer membrane proteins (YOPS)5. Plasminogen activator protease6. iron acquisition7. coagulase

Endotoxin lipid A of LPS

Antiphagocytic

*would want to target this to decrease virulence-expressed at low blood calcium levels-allows for expression of YOPS

-requires expression of Icr-have cytotoxic activity-resist phagocytic killing-initiates apoptosis in macrophages-suppresses cytokine formation and diminishes the inflammatory response to infection

-degrades fibrin clots-allows for spreading

Absorbs from host

-made at flea body temperature and only expressed at this temperature therefore not expressed in humans-blocks gut of flea so organism is stuck there so it can transmit/pass easier

Organism must first multiply in the gut of the flea to block food passageway and the blocked flea bites ferociously so that blood from the previous host is regurgitated1. bubonic plague2. pneumonic plague

-transmitted via flea bite-organism multiplies rapidly in lymph nodes producing a hemorrhagic necrosis leading to a painful swelling known as a bubo-usually in the groin or under arm-occurs 2-7 days following bite-accompanied by pain and fever-organism can spread to lungs, liver, spleen-leads to disseminated intravascular coagulation-death can occurs within hours of bubo development-no human to human transmission from buboes-if organism spreads to the lungs, leads to pneumonic plague which is highly infectious

-can follow bubonic plague or occur on its own (referred to as primary pneumonic plague)**highly infectious-if following bubonic plague-->lungs will be involved-->mucoid/bloody sputum-->respiratory droplets are highly contagious-if primary pneumonic plague-->incubation 2-3 days following inhalation of organism-->symptoms: fever, malaise, tightness in chest, cough, difficulty breathing, bloody sputumonce you develop symptoms, 100% mortality without treatmentantibiotics must be given within 18 hours of exposure