Enterobacteria/Pseudomonads Flashcards
Yersinia species
non-lactose fermenting, gram negative rods
Motile- i.e. those that cause enteric disease(not y. pestis)
Y. pestis (plague), Y. enterocolitica, Y. pseudotuberculosis (enteric disease, septicemia) pathogenic for animals and man.
Y. ruckeri causes perioral hemorrhage inflammation in fish
Demonstrate bipolar staining (look like safety pins) in Giemsa stained smears from animal tissues
Yersinia species ecology
Y.pseudotuberculosis and Y. enterocolitica in intestinal tract of wild mammals, birds, and domestic animals–reservoir of infection of foodborne pathogens in humans
All may be reservoirs of infection
Many avian species may act as amplifier hosts and may transfer organisms mechanically
Both organisms grow in wide temp. range (4-42)
In endemic areas, wild rodents are important reservoirs of Y. pestis. Fleas, especially Zenopsylla cheopis (oriental rat flea) transmit infection to man and other animals.
Y. enterocolitica
pigs and other domestic animals, wildlife: subclinical enteric infections, occasionally enteritis
ewes: sporadic abortion
humans: gastroenterocolitis
Y. pseudotuberculosis
farmed deer, sheep, goats, cattle, buffaloes, pigs: enteritis in young animals, subclinical infections common in older animals, mesenteric lymphadenitis
nb: mesenteric lymphadenitis- swollen mesenteric LNs–>severe abdominal pain–>masquerades as appendicitis
cattle, sheep, goats: sporadic abortion
g. pigs and other lab animals: focal hepatic necrosis, septicemia
caged birds: septicemia
humans: entercolitis, mesenteric lymphadenitis
Y. pestis
humans: bubonic and pneumonic plague
rodents: sylvatic plague
cats: feline plague.
Pathogenesis of Yersinia
pathogenic enteric yersinia invade some cells (M cells) of peyers patches and prevent uptake by other cells (phagocyte)
virulence: 70kb plasmid. plasmid and chromosomal encoded virulence factors required for survival and inhibit phaogcytosis by PMNs and macrophages.
TTSS secretes effector proteins into phagocytic cells- “YOPS”
Survival of Y. enterocolitica and Y. pseudotuberculosis is enhanced by anti-phagocytic proteins (Yops) secreted by organism (via TTSS) which interferes with normal functioning of neutrophils and macrophages in host.
This system allows extracellular bacteria adhering on surface of cells to secrete and inject bacterial effector proteins called Yops into the cytosol of the target cell in order to disable or alter function.
In GI mucosa, bacteria prevent phagocytosis, replicate in mesenteric lymph nodes with the development of necrotic lesions and neutrophil infiltration.
Clinical infections of yersinia
Y. pseudotuberculosis causes enteric infections which are often subclinical. Enteric disease caused by Y. pseudo is common in farmed deer in Australia and NZ (also, sheep, goats and cattle under 1 year)
Septicemia (pseudotuberculosis) occurs in lab rodents and aviary birds
Overcrowding, sudden, feather ruffling, necrotic foci in liver PM.
Treatment is seldom feasible due to acute nature of the disease
In rodents, organism introduced through contact with contaminated food or wild rodents.
Diarrhea and weight loss leads to emaciation and death. some die suddenly from septicemia.
Generally: yersinia pseudotuberculosis causes enteric disease in younger animals. Adults immune to disease but not carriage.
Clinical infections of Y. enterocolitica
wild and domestic animals may act as a reservoir for what is primarily a human enteric pathogen.
pig is a natural reservoir for y. enterocolitica serotype 03 biotype 4 which is an important pathogen in humans. –common in intensive pig production
Diagnosis of yersinia enterocolitica and y. pseudotuberculosis
histo exam of intestinal lesions
culture from feces, pus or tissue
plated on macconkey for growth at 37 or room temp
API 20E
cold enrichment
serotyping
Plague- yersinia pestis
caused by gram negative bacteria yersinia pestis (3 biotypes)
zoonotic infection in rodents, transferred by fleas
organism in blood of rodents, blood+organism taken up by fleas and flea bites human (or dog or cat)
Endemic in Africa, Asia, USA (southwest and pacific coast plague foci) (prairie dogs, ground squirrels, antelope, chipmunks, wood rats, deer mice)
potential bioterror weppon (pneumonic plague- person to person spread by airborne route).
Sylvatic and urban cycles of yersinia
Sylvatic: infective flea–>man
wild rodent–> direct contact with man
Urban: domestic rodent and infective flea can both infect man
Susceptibility to yersinia pestis
susceptibilities of different wild rodent species to plague mortality vary greatly.
praire dog of western N.america is extremely susceptible
epizootics among colonies of these animals spread very quickly and may cause greater than 99% mortality
other rodents, such as kangaroo rats in N. america can be infected but are relatively resistant and apparently suffer few ill effects.
Certain species have both highly susceptible and relatively resistant populations.
Clinical infection of y. pestis
can infect both dogs and cats in endemic areas. cats are particularly susceptible and may be a source of infection for owners and attending vets
Usually acquired by ingesting infected rodents
bubonic, septicemic, pneumonic
cats with pneumonic plague are a source of human infection through aerosol generation and should be euthanized.
human infection acquired through cat scratches and bites and fleas from infected cats.
Plague syndromes in man
bubonic: fever, painful lymphadenopathy (bubo)
Septcemic: fever, hypotension with or w/out bubo
Pneumonic: cough, hemoptysis (expectoration of blood), with or w/out bubo
Meningitis: fever, nuchal rigidity usually with bubo
Virulence factors specific to Y. pestis
Fraction 1 (F1) antigen: capsule (made of polypeptide NOT polysaccharide) around bacteria- plasmid encoded- prevents opsonisation
HPI for Iron acquistion (also Ye, Yp)
Ymt protein on plasma is a phospholipase D required for survival in flea midgut
Hms locus required for efficient transmission to sub cut. sites. Bacilli lacking hms replicate in flea midgut but don’t lodge en masse in proventriculus. Hms delivers infectious dose by bypassing organisms in proventriculus.
Pla is plasmid encoded and is essential for Y. pestis to disseminate from sub cut site of inoculation to LNs or blood. Pla is enzymes that allows dissemination
