Streptococci Flashcards
Strep description
G+ve
Cocci
Usually in chains
Commensal and pathogenic on skin and mucous mems
Classification
Grps: pyogenic, enterococci, oral, lactic, other
Based on factors incl haemolysis, Ce antigs and fermentation properties
Beta haemolytic
Complete haemolysis (clear zone produced)
Alpha haemolytic
Incomplete haemolysis or green discolouration
Non haemolyctic or gamma haemolytic
No haemolysis
CW antigen classification
Basis for lancefield test
Carbs from polysacc, teichoic and lipoteichoic acid in the CW
Other serological diff (eg M pro) allow further subdivision
Carb fermentation
Range of sugars fermented somewhat correlates to species
Pyogenic strep summary
Long chains
Beta haem
A B C G L lancefield grps
Viridans summary
Long chains
Alpha haem
Not typable by lancefield
Pneumococci summary
Pairs
Alpha haem
Not typable by lancefield
Enterococci summary
Short chain
Any haem
D grp lancefield
Lancefield process
Extracted with hot HCL wnd ppt with Ab from rabbits
Refer to as gro polysacc and assigned letter
21 grps IDed but ltd prac value
Human strep
Pyogenes (A)
Agalactiae (B)
Canine strep
Canis (G)
Pneumoniae (NT)
Equine strep
Equi
Equisimilis
Zooepidemicus
All C
Cattle strep
Zooepidemicus (C)
Agalactiae (B)
Dysgalactiae (C)
Uberis (NT)
Pig strep
Suis (D)
Porcinus (E)
Strep equi
C
Obligate parasite
Not commensal but can be ‘carried’ in tonsils and guttural pouch asympt
Cause strangles
Strangles symptoms early
Abrupt fever 103+ degrees c
Pharyngitis causing dysphagia neck extended listless depressed reluctant to eat
Pharyngitis laryngitis rhinitis may contrib to nasal discharge
Later strangles symptoms
Lymphadenopathy sub mand and retropharyngeal l nodes equally involved
Painful oedema
Swollen and painful a wk post
Serum ooze from overlying skin for days before rupture
Drains tenacious creamy pus
What is strangles
Highly contagious resp disease affecting horses under 5 potentially fatal
Causes major farm disruption and there is widespread distribution
Suppurative pharyngitis and lymphadentis
How are zooepidemicus and equisimilis differ from equi
Often present as nasopharyngeal colonisers in normal horses but less host adaptive, both opportunistic pathogens causing mastitis local sepsis endometritis abortion endocarditis etc
Zooepi can cause infection of resp tract secondarily eg to influenza
What is bastard strangles
Normal strangles mainly restricted to upper airways but. Septicaemia resulting from strangles due to metastasis to other locations
Involves bacteraemia and abscesses in other lymph nodes, organs of thorax and abdomen rarely infect brain too
Haemorrhagic purpura can occur (widespread blood vessel damage, swelling of head legs and bruise like patches on mouth)
Often fatal
Strangles pathogenesis
Inflam resp to invasion cause neutro and serum influx
Many strep virulence factors interfere with phagocytosis
Destruction of bact and phagosome causes viscous mix of protease, lytic enz and dead cells that extend area of tissue damage
How do bact protect themselves from opsonisation
M pro and capsule and cause host cell lusis by secr streptolysinsnakd othe EC enz
Virulence factor: peptidoglycan
Chemotactic for PMNs and pyrogenic
Virulence factor: fibronectin binding pros
Involved in cellular invasion
Virulence factor: M pro and M like pro
Req for virulence
Pro fibril allowing to bind fibrinogen fibrin and their degradation products to form dense coat over bacteria to protect from complement
Also protect against opsonisation by bind factor H
M like bind fibronectin IgA and G to aid evasion
Virulence factor: ZAG pro
Bind Ab Fc part
Virulence factor: capsule
Protect against phagocytosis
Weakly immunogenic
Virulence factor: C5a peptidase
Cleave C5a
Virulence factor: hyaluronidase NADase and streptokinase
H: facilitate spreading in tissues
S: break down fibrin clots
N: inhib PMN activity and is leukocidal
Virulence factor: SLO and SLS
SLO: O2 labile. Bind cholesterol in mem to form pores
SLS: O2 stable.
Both contrib to pyogenic strep beta haem
Induce cytok release and active against leukocyte chemotaxis degran and lysis
Virulence factor: superoxide dismutase
Neutralise antibac O2 free radicals prod
Virulence factor: degradative enz
Release nutrients from host
Virulence factor: strep pyrogenic exotoxins
Prod by some strains
Mainly grp A
Superantigens so are highly pro inflam and immunomodulatory
Strangles diagnosis
Nasopharyngeal swab and culture or wash or pus from abscess on columbia blood agar
Can hive -ve result, washes are more sensitive esp during early incubation if you spin down wash and culture the pellet.
PCR detection much more sensitive
Strangles epidemiology
Purulent discharge
Horse-horse contact
Indirect transmission
Carriers
Strangles treatment
Penicillin, most are resistant to eg ampicillin
Not always effective
Immunity after natural strangles infection
75% dev over 5yr long imm
So a giid vacc should be feasible
Vacc possibilities
M pro and capsules poorly antigenic but can induce spec IgG and A giving partial/complete imm
Ab also prod to haemolysins
M pro considered as potential vacc immunogen
No reliable vacc yet, approacge involving m pro have failed to prevent outbreaks
Control during strangles outbreak
Stop horse movement in and out
Quarantine
Antibio treatment
Control of strangles after clinical recovery
Over 3 swabs at 1 wk intervals
Quarantine
Strict hygiene introduced
Strep mastitis caused by
Grp A aka Pyogenes mainly in humans
Other grps more predom in animals
Mastitis by agalactiae
Grp B
Chronic contagious bovine mastitis
Obligate mammary gland parasite
Adhere to and grow along the teat and duct sinuses causing mild, chronic inflam and fibrosis
Can cause small duct blockage and loss of milk prod capacity
Mastitis by dysgalactiae
Grp C commensal of mouth and udder
May invade wounds and cause mastitis or summer mastitis in assoc with arcanobacterium pyogenes
Acute can cause permanent quarter damage
Mastitis by uberis and parauberis
Untypable viridan like
Surf commensals
Can cause mastitis under poor enviro or management conditions
Survives and transmitted via bedding
Enviro mastitis
Can occur during dry period and may be severe
Strep suis
Endemic in pig industry
Usually asympt can cause septicaemia meningutis pneumonia and arthritis
Young pigs most at risk
Strep suis predisposing factors
Poor housing with inadeq ventilation
Esp if under intensive conditions that can cause stress leading to imm suppr
Strep suis in humans
Most recent outbreak coincided with pig outbreak
No human to hunan transmission
All affected in contact with pigs
Most people affected had typical strep TSS symptoms
High morbidity and mortality rate
Now under WHO surveillance
