Gram negative facultative anaerobic rods

Question 0

Escherichia coli

Answer 0

Lactose fermentor
Four main types of antigens. O,K,H,F
Diarrhea in newborns
Septicemia in newborn calves, lambs, and piglets
Mastitis in cows, sows, and ewes
Cystitis/polynephritis in bladders, may reach kidneys
Food poisoning enterotoxins
Human pathogen in 1982
0157:H7 is pathogenic strain
Found in foods, flies, manure, ponds, soil, water

Question 1

Enterobacteraceae

Answer 1

Family of a large number of organisms

May have flagella, capsule, or pili

Question 2

Enterobacter aerogenes

Answer 2

Weak lactose fermenters
Does not often cause problems
Can cause mastitis, metritis, or polynephritis

Question 3

Klebsiella pneumoniae

Answer 3

In shavings used as bedding, soil, or decaying vegetables
Weak lactose fermenters
Mastitis (opportunistic)
Metritis
Polynephritis

Question 4

Proteus vulgaris

Answer 4

Foul smelling
Swarming on MAC
Non lactose fermentor
Cystitis/polynephritis (third most common invader in small animals)
Granulomatous dermatitis in dogs
Otitis media ear infections in dogs
Diarrhea - secondary cause in animals on prolonged antibiotic therapy.

Question 5

Salmonella

Answer 5

Three main groups: affects only humans, only animals, and affects animals and humans.
Non lactose fermentor with black centre due to H2S production.
Selective media used: ex. Brilliant green, bismuth sulphite agar, ss media, xlt4 agar.
Liquid enrichment media may be needed in samples with low numbers: tetrathionate and selenite F.
Many rapid tests (ex. Snap tests or ELISA tests)
Kaufmanns white scheme tests for the three antigens (O,Vi,H)
Reportable disease except for horses and small animals.
Septicemia in newborns
Acute diarrhea/dysentery at any age
Abortion in cows and ewes.
Localization in other tissues

Question 6

Salmonella continued.

Answer 6

Carriers may shed for weeks, months, or longer.
Diagnose from fecal sample, blood culture, serology, or rectal biopsy
Humans only: S. typhi, S. paratyphoid
Humans and animals: S. typherium, S. enteritidis
Animals only: cows- S. Dublin, S.newport
Horses- S. abortus equi
Sheep- S. abortus ovis, S. dublin
Pigs- S. choleraesuis

Question 7

Yersinia pestis

Answer 7

May use chocolate agar
Known in the plague
Bubonic form: start of epidemics, transmitted through bites of infected fleas
Pneumonic form: highly contagious, fatal spreads human to human through respiratory droplets.