SI and LI microbiology

Question 1

Why is infection in the oesophagus uncommon?

Answer 1

rapid passage of material
Tough stratified epithelium

Question 2

What are the notifiable infections of the oesophagus?

Answer 2

BVDV (bovine viral diarrhoea virus)
Ovine herpes virus (mucosal disease)
Newcastle disease (poultry)

Question 3

Describe enterobacteriaceae

Answer 3

gram -ve rods
oxidise negative, facultative anaerobes
Grow on MacMonkey

Question 4

What are the major enteric enterobacteriaceae pathogens?

Answer 4

Escherichia coli
Salmonella enterica
Yersinia

Question 5

Describe the major opportunistic enterobacteriaceae pathogens

Answer 5

Proteus species
Enterobacter species
Klebsiella species

Question 6

What are the common methods for differentiation of enterobacteriaceae?

Answer 6

PCR of unique genes
Whole genome sequence
Ribosomal genome sequence
Mass spectrophotometry

Question 7

Which E.coli pathotypes cause enteric disease

Answer 7

Enterotoxigenic E.coli
Attaching and effacing E.coli
Enteroaggregative E.coli

Question 8

What is the LEE (locus of enterocyte effacement) of E.coli?

Answer 8

Gene island that encodes for a type 3 secretion system (TTSS)
Translocates intimin receptor into host cell which the bacteria attaches to
This is what forms the attaching and effacing lesion of AEEC E.coli

Question 9

What factors can lead to infection of young animals with pathogenic E.coli?

Answer 9

Poor colostrum immunity
Receptors:
- enterotoxigenic E.coli receptors in calves for first few weeks of life
Build up of pathogenic E.coli:
- change in digestion and/or types of food allows E.coli build up
stress and environment:
- overcrowding, poor hygiene

Question 10

What are the 2 species of salmonella?

Answer 10

S. bongori
S. enterica

Question 11

What are the important serotypes of salmonella enterica?

Answer 11

S. gallinarum - chicks
S. pullorum - adult poultry
S. enteritidis - poultry
S. typhimurium - cattle, sheep, horses, dogs
S. dublin - cattle, sheep, horses, dogs
S. cholerasuis - pigs

Question 12

where is salmonella found?

Answer 12

contaminated water sources
carrier animals
Faecal contaminated environment
Eggs from infected birds
Raw meat (contaminated faecal material spreads during slaughter)
Offal
Animal feed
Plant material (faecal contamination and uptake)

Question 13

Describe the pathology of enteric salmonellosis

Answer 13

Attachment and invasion
Penetration of mucosal barrier, inflammation and fluid secretion
Neutrophils attracted to site and into lumen of villi
Infection of macrophages

Question 14

What are the clinical signs of enteric salmonellosis?

Answer 14

Fever
Depression
Anorexia
Recumbent if severe

Question 15

Describe the role of type III secretion systems in enteric salmonella

Answer 15

TTSS-1:
- injects effector proteins into host enterocyte
- effector proteins:
=> trigger invasion by actin and tubulin remodelling
=> trigger cytokine response
=> trigger fluid secretion from enterocytes

TTSS-2:
- injects SPI-2 effectors:
=> stop cytoskeletal movements in cells so cell cannot mature vacuoles
=> Salmonella in protected space

Question 16

Describe septicaemic salmonella

Answer 16

disease spread from gut via invasion into blood and lymph inside macrophages
Spreads to liver and spleen
=> sudden high fever, depression, recumbence, rapid death

Question 17

Describe the effect of salmonella in poultry and eggs

Answer 17

Salmonella bacteria found in macrophages which reach oviducts and contaminate eggs (fowl typhoid)
S. enteritidis
S. gallinarum

Question 18

Describe the detection of salmonella

Answer 18

Enrichment in selenite broth
Direct inoculation onto MacMonkey or XLD agar
Suspect colonies confirmed with serotyping/mass spec

Question 19

describe campylobacter bacteria

Answer 19

Gram -ve
vibrio
flagella (motile)

Question 20

What are the most common intestinal species of campylobacter

Answer 20

C. jejuni
C. coli
C. lari

Question 21

Describe the disease process of campylobacter

Answer 21

Infection of poultry with no obvious disease - contamination of meat
Contaminated meat => ingested => colonises intestines => inflammation => tissue damage => secretion and fluid release => inflammatory diarrhoea

Question 22

Where on the farm can you sample to identify campylobacter?

Answer 22

Environmental samples
faecal swabs
Boot swabs

Question 23

Where in the abattoir can you sample to identify campylobacter?

Answer 23

gut contents (Caecum)
neck swabs from birds
skin samples

Question 24

Where at retail can you sample to identify campylobacter?

Answer 24

swabs
juice from meat packages
whole meat samples

Question 25

What is MLST (multi locus sequence typing)?

Answer 25

looks at single base pair changes by sequencing housekeeping genes and clustering strains based on differences (=> clades)
If a clinical isolate clusters in an MLST clade it indicates potential source of infection

Question 26

What is the impact of campylobacter on birds?

Answer 26

inflammation during initial colonisation => reduced weight gain, hock burn

Question 27

Describe campylobacter in dogs

Answer 27

Often found in healthy animals
Large number of campylobacter indicates infection

Question 28

What are the important brachyspira species?

Answer 28

B. hyodysenteriae - pigs and poultry
B. innocens - pigs and poultry
B. pilosicoli - poultry, pigs, horses, dogs
B.intermedia - pigs and poultry
B avinipulli - poultry

Question 29

Describe brachyspira species

Answer 29

Anaerobic
Spiral motile bacteria
gram -ve

Question 30

What methods are used for diagnosis of brachyspira?

Answer 30

selective media
stained faecal smear
PCR

Question 31

Describe pathogenesis of brachyspira

Answer 31

Motility in gastric mucous essential
Haemolytic activity correlates with virulence
Mucosal disruption => cell shedding and oedema

Question 32

Describe lawsonia species

Answer 32

Curved gram -ve rod
obligate intracellular pathogen
Microaerophilic

Question 33

Describe the diagnosis of lawsonia

Answer 33

clinical signs
immunofluorescence or PCR of mucosa or faeces
Staining of tissue secretions
Serological tests

Question 34

Describe the pathology of lawsonia intracellularis

Answer 34

Invades enterocytes
Causes lack of differentiation
Undeveloped cells do not shed
=> pseudo-stratified epithelium
=> thickening of gut wall => poor absorption