Small gram negatives and gram negative anaerobes

Question 1

Brucella- general characteristics

Answer 1

Small gram negative coccobacili
non-motile, non-sporing, non-fermentative, aerobe
oxidase positive
visualized by modified Z-N stain
requires complex media for growth (i.e. blood)
growth enhanced by CO2
predilection for male and female repro tracts
organism can be acquired via inhalation, ingestion or direct contact

Question 2

B. abortus

Answer 2

Cattle: contagious bovine abortion, orchitis,
Sheep goats pigs: sporadic abortion
humans: undulant fever- remitting fever localized to musculoskeletal system

Question 3

B. melitensis

Answer 3

Sheep and goats: orchitis and obrtion

HumansL malta fever

Question 4

B. ovis

Answer 4

Sheep: abortion and epidiymitis

Question 5

B. canis

Answer 5

dogs: abortion, epididymitis and arthritis
Humans: mild infection

Question 6

B. suis

Answer 6

pigs: abortion, infertility, orchitis, arthritis
humans: undulant fever

Question 7

B. neotomae

Answer 7

rodents

Question 8

Brucella pathogenesis

Answer 8

Prevention of phagolysosome fusion to allow intracellular survival
Penetrate mucosa (usually GI)–> move to regional LN via macrophages and multiply in LN
Phaogcytosis/invasion–> proliferation/persistence/ bacteremia–> dissemination
tropism for repro tissue
Milk becomes infectious if disseminated to udder.

Question 9

B. melitensis genome

Answer 9

2 chromosomes with 2300 genes.
closest relatives are plant symbionts and plant pathogens
Lacks many of the expected virulence systems: no TTSS, no fimbriae, no secreted toxins, no capsule
Pathogenesis depends on intracellular survival.
Putative virulence genes identified
Type IV secretion system- diff. in structure but it also injects effector proteins.

Question 10

Brucella pathogenesis

Answer 10

We don’t know a lot about brucella virulence
intracellular pathogen- many cell types
survives within the macrophages (and also epithelial and endothelial cells)
-inhibits phagolysosome fusion and actively replicates in macrophore cells.
Preferred carbon source is erythritol- present in high concentration in placenta of cattle, sheep goats and pigs, however, if you knock out erythritol in mice, doesn’t change the outcome, but erythritol isn’t the predominant CHO in mouse placenta.
Siderophore, iron uptake.

Question 11

Brucella: persistent infection

Answer 11

Surivival within the macrophages: inhibits phagolysosome fusion
Type IV secretion system
Cylic Beta 1,2-glucan in brucella virulence factor required for intracellular survival
Doesn’t alarm the host- brucella LPS 1000 times less pro-inflammatory than E. coli. Body doesn’t recognized it well–>stealth pathogen.

Question 12

Bovine brucellosis in GB: eradication

Answer 12

1934- ~40% of cattle herds brucella positive
a a free calf vax scheme S19 vaccine in 1962
voluntary attested herd scheme 1967
compulsory area eradication 1971
disease free, vaccine program ended in 1979
brucellosis free status gained in 1991 from EU

Question 13

Human brucellosis

Answer 13

no human to human transmission
zoonosis via direct contact or unpasteurized dairy products
One of the leading zoonoses worldwide.

Question 14

Brucella screening

Answer 14

detect antibody in serum (milk against brucella LPS)
Milk ring test: test milk using labelled antibodies–> get precipitation if there are anti-brucella antibodies.
ELISA, Serum agglutination test
False positives: ABs cross react with LPS of other bacteria; shares similar O group to Yersinia enterocolitica

Question 15

Brucella vaccines

Answer 15

live vaccines, chemical mutagens
smooth strain: not attenuated for humans due to intact LPS
rough strain: non intact LPS- lack O side chain. look rough on culture.
useful to distinguish between vaccinated animals and naturally infected. rough strain is obviously vaccinated.

Question 16

Bordetella-general characteristics

Answer 16

small gram negative coccobacilli
strict aerobe
oxidase positive
non-sporing, most motile
don't ferment CHOs
respiratory tract pathogens mammals and birds

Question 17

B. bronchiseptica

Answer 17

Dogs: kennel cough
Cats: resp infections/ acute pneumonia
Pigs: progressive atropic rhinitis with Pasturella multocida, bronchopneumonia
Many species: respiratory infections

Question 18

B. parapertussis

Answer 18

Sheep: resp infections
Humans: whooping cough
not zoonotic infection- separate sheep/human strains

Question 19

B. avium

Answer 19

turkeys: resp infections

Question 20

B. pertussis

Answer 20

human whooping cough

Question 21

B. bronchiseptica cultural characteristics

Answer 21

grows on macconkey agar
NLF–> produces urease, lowers pH–Characteristic yellow.
since it grows on macconkey agar and doesn’t produce pink colonies (NLF)–useful to distinguish from most gram negative resp. pathogens

Question 22

Strategies of extracellular pathogens

Answer 22

Likes to survive outside cells
counteract complement
counteract phagocytes
acquire nutrients
bordetella has toxins involved with pathogenesis.

Question 23

Adhesion of B. bronchispetica to ciliated respiratory cells

Answer 23

ciliated epithelial cells trap organisms–> get swallowed.
bordetella adheres to these cells
organisms not being swept back. bordetella gets stuck to the mucociliary elevator.

Question 24

Pathogenesis of bordetella

Answer 24

Initial attachment of B. bronchiseptica to ciliated cells- done by specific adhesins
Tight adhesion to cilia
Production of toxins
paralyse cilia
Loss of cilia
interference with innate and specific IR
Accumulation of mucus–> presentation of disease in kennel cough

Question 25

Bordetella virulence factors

Answer 25

Fimbriae: bind to tissue
Filamentous hemagglutinin (FHA)
Pertactin- outer membrane protein
These three act as adhesins to attach to host tissue.

Adenylate cyclase toxin, tracheal cytotxin and dermonecrotoxin all cause tissue dmage and counteract host defences
TTSS: subversion of host defense mechanisms

Question 26

Adenylate cyclase toxin

Answer 26

adenylate cyclase= bacterial enzyme 
RTX toxin (repeat structure): hemolysin, damages WBCs

RTX binds to host cell surface. Adenylate cyclase enters and activates calmodulin. This increases the cAMP in tissue causing a fluid influx into the tissue (edema). This decreases chemotaxis, and decreases phagocytosis

Question 27

Tracheal cytotoxin

Answer 27

not a classic toxin. sheds TCT (fragment of peptidoglycan) and LPS. These have effect on epithelial cells. Bind and internalize into epithelial cells. Increase IL-1 which increases nitric oxide. The nitric oxide is responsible for the cilia loss.
Increases susceptibility to other respiratory infection as well–> secondary bacterial pneumonia.

Question 28

Regulation of bordetella virulence

Answer 28

2 compoonent regulatory system
BvgS- sensor kinase- phosphorylate and de-phosphorylate- present in membrane and
BvgA- present in cytoplasm- transcriptional activator. BvgA acts as a thermostat. At 37 degrees, S phosphorylates A and virulence genes are expressed. At 25 degrees, A is de-phosphorylated and the virulence genes are not expressed.

Having the virulence genes on all the time is wasteful.

Question 29

Pathogeneis of atropic rhinitis in pigs

Answer 29

Synergistic infection with pasturella multocida and bord. bronchiseptica
Initial attachment of B. bronch to ciliated cells
Tight adhesion to the cells–> production of toxin–> paralyse cilia
loss of cilia–> interference with innate and specific IR, accumulation of mucus.
Colonisation of toxigenic p. multocida types A or D–> P. mutlocida toxin responsible for destruction of turbinates.

Question 30

Bronchiseptica vaccines

Answer 30

available for cats and dogs
live attenuated, not defined
administered intranasally- produces mucosal immunity where organism tries to infect.
mucosal IgA important for immunity

Question 31

Gram negative anaerobes

Answer 31

non-sporing, gram negatives, anaerobic

Question 32

Anaerobic bacterial infections

Answer 32

Anaerobic bacteria require anaerobic conditions, need negative redox potential Eh for growth.
They can grow in lumen of the LI and rumen. Also found on any mucosal surface. Large numbers in the mouth, gut, genitourinary system
Elsewhere (if not on mucosal surface), they require loss of blood supply or necrotic conditions or population of aerobes/facultative anaerobes which reduces the oxygen tension.–> often cause mixed infection.

Question 33

Anaerobic, non-sporing gram negative species

Answer 33

Fusobacterium necrophorum
Dichelobacter nodosus
Bacteroides sp.
Prevotella sp.
Porphyromonas sp.

Question 34

Polymicrobial infections

Answer 34

Foot rot: dichelobacter nodusus (mainly caused by this but need damage from other bacteria)
fusobacterium necrophorum
a. pygoenes
spirochetes, and others
Abscesses: bacteroides fragilis and e. coli (facultative aerobe)

Question 35

Pathogenesis of foot rot

Answer 35

Predisposing conditions: wetting, trauma, etc
primary colonisation: facultative anaerobe (e.g. trueperella pyogenes)
secondary colonisation: F necrophorum–local superficial inflammation (dermatitis)
Tertiary colonisation: Dichelobacter nodosus- causes severe symptoms- ulceration, hoof destruction–> chronic lameness

Question 36

Dichelobacter nodosus

Answer 36

strict anaerobic gram negative, non-sporing
long-clubbed ends
footrot in sheep
type IV fimbriae- can’t be pathogenic w/out this
Several proteases to digest hoof tissue
pathogenicity island?

Question 37

Fusobacterium necrophorum infections

Answer 37

Cattle: calf diphtheria- necrotic laryngitis, post-partum metritis, hepatic abscesses, black spot of teat.
Pig: necrotic rhinitis
horses: necrobacilliosis of lower limb, thrush of hoof.

Question 38

Fusobacterium

Answer 38

obligate anaerobe, non-sporing, gram negative (pleomoprhic) rods
virulence factors: leukotoxin, hemolysins and proteases

Question 39

Bacteroids, prevotella and porphyomonas species

Answer 39

gram negative rods, obligate anaerobes
All pyogenic, may cause abscesses, soft tissue infections
pus is foul smelling
Some bacteroides fragilis strains produce an enterotoxin and cause cause diarrhea in lambs, calves, piglets, foals and children.
produce BLACK pigment on culture.