Lymph And Blood Organisms

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A 44 yr old male archaeologist presents with high fever, malaise, intense headache, sever myalgia, and painful swelling in the inguinal region. He recently returned from a trip to Arizona. He presents with tachycardia, drowsy looking; no meningeal signs; pustule seen at site of an insect bite on left upper arm; inguinal lymph nodes enlarged, fluctuant, and tender; no lesion on external genitalia. His CBC/PBS: normal; no malarial parasites. Gram-negative bacilli with "safety pin" appearance seen in aspirates from buboes.

Back 1

Yersinia pestis

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Yersinia is in what family?

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Enterobacteriaceae

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Yersinis pestis is transmitted by?

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flea

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Y enterecolitica and Y pseudotuberculosis causes

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GIT infections

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Is Y pestis a cause of GIT infections?

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no

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Yersinia pestis characteristics

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gram -
bipolar staining
non motile
Wright-Giemsa stain
growth @ 28-30 degrees C

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What is a Plague?

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descriptive term for any explosive pandemic disease with high mortality; medically it refers only to infection caused by Y. pestis

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Y pestis plague

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most explosively virulent disease known; most virulent epidemic ever recorded; all clinical forms of disease are toxic and produce shock and death within a few days untreated

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Y pestis is transmitted by?

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via bite of infected rat flea or respiratory droplets of pneumonic plague patients

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Y pestis virulence factors

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endotoxin - cause of systemic effects of infectopn
gangrene
DIC - most common cause of death
& facultative intracellular pathogen of macrophages

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Y pestis plasmid encoded virulence factors

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expression istemp and Ca++ dependent
pYV
pFra
pPst

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pYV

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cluster of virulence genes (pathogenicity island)
-type 3 secretion system proteins
- Yersinia outer membrane proteins (Yop)
--- YopH (serine threonine kinase & tyrosine phosphatase - inhibits phagocytosis)
--- YopE (disrupt actin filaments)
--- Yop J/P (initiate macrophage apoptosis

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pFra

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Capsular F1 protein antigen (anti-phagocytic)

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pPst

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-plasminogen activator (Pla) preotease (dissemination)
- degrades C3b, C5a, and fibrin clots

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Sylvatic transmission

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-from wild rodents to wild rodents by fleas
(prairie dogs, deer mice, wood rats, rabbits, squirrels)
poor transmission to humans (sporadic incidence; usually a child who finds a dead or dying infected rodent)

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Urban plague transmission

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between rats in urban population centers by fleas (Black/Norway rats); something happens that decreases rat populationa nd flea wants food source (human); human to human transmission possible (pneumonic form)

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Plague Pathogenesis

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-multiplies in gut of infected flea and blocks foregut (flea regurgitates contents into blood/tissue of host)
-virulence factors need increased temp, decreased Ca++, and increased nutrient availability

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Bubonic/Septicemic plague characterized by

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hemorrhage
suppuration
necrosis
very painful
(bubos-lymphadenitis)

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Septicemic plague
other traits

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develops with treatment
50-70% mortality
dissemination to lungs, liver, spleen, CNS
Endotoxin exerts toxic effect in affected tissues (DIC, gangrene)
Black Death

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Sources of pneumonic plague

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inhalation of droplet nuclei from infected patient
septicemic spread of infection from other sites

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pneumonic plague traits

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hemorrhagic consolidation in lungs
highly infectious
untreated - death in 2-3 days (100% mortality)

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Diagnosis - agent of concern

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-extremely biohazardous
gram negative (bipolar staining - safety pin appearance)
slower growth but adequate @ 48 hrs

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Y pestis test characteristics

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oxidase negative
nonlactose fermentor
catalase positive
nonmotile @ room temperature

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Treatment of Y pestis

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Streptomycin and tretracycline are highly effective

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Y pestis immunity

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both antibody and cell-mediated
long lasting protective immunity

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Y pestis protection

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vaccination
-formaldehyde killed bacterial culture
-given only to those at highest risk (lab and health care givers who are exposed; vets)

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A 28 yr old white male visits his family doctor complaining of acute pain in both hip joints together with weakness, backache, myalgias, arthralgias, and undulating fever of 2 months' duration; this morning he woke up with pain in his right testicle. For the past 3 years he has worked at the largest dairy farm in his state. He enjoys drinking "crude" milk. He presents with fever, pallor; marked pain on palpation of sacroiliac joints; mild splenomegaly; generalized lymphadenopathy. CBC presents relative lymphocytosis with normal WBC count. Positive agglutination titer (>1:160); rising serologic titer over time; small gram-negative rod on blood culture. Hips present with joint effusion and soft tissue swelling without destruction. His spine has evidence of spondylitis. He shows lymphadenopathy and splenomegaly. He is treated with a combination therapy with doxycycline or TMP-SMX and rifampin or streptomycin.

Back 27

Brucellosis
Bang's disease, undulant fever, Malta fever

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Brucellosis
source of human infections

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pigs, cattle, goats, and sheep
acquire by direct contact with contaminated tissue or by products (unpasteurized milk)
abrasions or cuts in skin
contact with mucous membranes
inhalation or ingestion

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brucellosis
cause disease in animals

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causes genito-urinary infection in animals
important cause of abortion, sterility, and decreased milk production in cows
slow growing and very fastidious

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Brucellosis
pathogenesis

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human infection is chronic (acquired by many routes)
disease of reticuloendothelial system (small granulomas and bacteremic episodes - recurrent fevers and chills)
infects macrophages and epithelial cells at initial site of infection

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Brucellosis
disseminates...

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disseminates into liver sinusoids, spleen, bone marrow, and other organs of the RES system: lymphoid tissues

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Brucellosis
virulence factors

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suppresses myeloperoxidase system
inhibits phagosome-lysosome fusion
inhibits monocyte cytokine production (TNF -alpha)

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Does human placenta contain erythritol?

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No. In animals, a four carbon alcohol, ertythritol present in chorionic tissue stimulates bacterial growth and accounts for site of infection.