SI and LI microbiology Flashcards
Why is infection in the oesophagus uncommon?
rapid passage of material
Tough stratified epithelium
What are the notifiable infections of the oesophagus?
BVDV (bovine viral diarrhoea virus)
Ovine herpes virus (mucosal disease)
Newcastle disease (poultry)
Describe enterobacteriaceae
gram -ve rods
oxidise negative, facultative anaerobes
Grow on MacMonkey
What are the major enteric enterobacteriaceae pathogens?
Escherichia coli
Salmonella enterica
Yersinia
Describe the major opportunistic enterobacteriaceae pathogens
Proteus species
Enterobacter species
Klebsiella species
What are the common methods for differentiation of enterobacteriaceae?
PCR of unique genes
Whole genome sequence
Ribosomal genome sequence
Mass spectrophotometry
Which E.coli pathotypes cause enteric disease
Enterotoxigenic E.coli
Attaching and effacing E.coli
Enteroaggregative E.coli
What is the LEE (locus of enterocyte effacement) of E.coli?
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
What factors can lead to infection of young animals with pathogenic E.coli?
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
What are the 2 species of salmonella?
S. bongori
S. enterica
What are the important serotypes of salmonella enterica?
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
where is salmonella found?
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)
Describe the pathology of enteric salmonellosis
Attachment and invasion
Penetration of mucosal barrier, inflammation and fluid secretion
Neutrophils attracted to site and into lumen of villi
Infection of macrophages
What are the clinical signs of enteric salmonellosis?
Fever
Depression
Anorexia
Recumbent if severe
Describe the role of type III secretion systems in enteric salmonella
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
Describe septicaemic salmonella
disease spread from gut via invasion into blood and lymph inside macrophages
Spreads to liver and spleen
=> sudden high fever, depression, recumbence, rapid death
Describe the effect of salmonella in poultry and eggs
Salmonella bacteria found in macrophages which reach oviducts and contaminate eggs (fowl typhoid)
S. enteritidis
S. gallinarum
Describe the detection of salmonella
Enrichment in selenite broth
Direct inoculation onto MacMonkey or XLD agar
Suspect colonies confirmed with serotyping/mass spec
describe campylobacter bacteria
Gram -ve
vibrio
flagella (motile)
What are the most common intestinal species of campylobacter
C. jejuni
C. coli
C. lari
Describe the disease process of campylobacter
Infection of poultry with no obvious disease - contamination of meat
Contaminated meat => ingested => colonises intestines => inflammation => tissue damage => secretion and fluid release => inflammatory diarrhoea
Where on the farm can you sample to identify campylobacter?
Environmental samples
faecal swabs
Boot swabs
Where in the abattoir can you sample to identify campylobacter?
gut contents (Caecum)
neck swabs from birds
skin samples
Where at retail can you sample to identify campylobacter?
swabs
juice from meat packages
whole meat samples
What is MLST (multi locus sequence typing)?
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
What is the impact of campylobacter on birds?
inflammation during initial colonisation => reduced weight gain, hock burn
Describe campylobacter in dogs
Often found in healthy animals
Large number of campylobacter indicates infection
What are the important brachyspira species?
B. hyodysenteriae - pigs and poultry
B. innocens - pigs and poultry
B. pilosicoli - poultry, pigs, horses, dogs
B.intermedia - pigs and poultry
B avinipulli - poultry
Describe brachyspira species
Anaerobic
Spiral motile bacteria
gram -ve
What methods are used for diagnosis of brachyspira?
selective media
stained faecal smear
PCR
Describe pathogenesis of brachyspira
Motility in gastric mucous essential
Haemolytic activity correlates with virulence
Mucosal disruption => cell shedding and oedema
Describe lawsonia species
Curved gram -ve rod
obligate intracellular pathogen
Microaerophilic
Describe the diagnosis of lawsonia
clinical signs
immunofluorescence or PCR of mucosa or faeces
Staining of tissue secretions
Serological tests
Describe the pathology of lawsonia intracellularis
Invades enterocytes
Causes lack of differentiation
Undeveloped cells do not shed
=> pseudo-stratified epithelium
=> thickening of gut wall => poor absorption
