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Bacteriology > Streptococci > Flashcards

Streptococci Flashcards

1
Q

Strep description

A

G+ve
Cocci
Usually in chains
Commensal and pathogenic on skin and mucous mems

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2
Q

Classification

A

Grps: pyogenic, enterococci, oral, lactic, other

Based on factors incl haemolysis, Ce antigs and fermentation properties

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3
Q

Beta haemolytic

A

Complete haemolysis (clear zone produced)

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4
Q

Alpha haemolytic

A

Incomplete haemolysis or green discolouration

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5
Q

Non haemolyctic or gamma haemolytic

A

No haemolysis

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6
Q

CW antigen classification

A

Basis for lancefield test
Carbs from polysacc, teichoic and lipoteichoic acid in the CW
Other serological diff (eg M pro) allow further subdivision

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7
Q

Carb fermentation

A

Range of sugars fermented somewhat correlates to species

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8
Q

Pyogenic strep summary

A

Long chains
Beta haem
A B C G L lancefield grps

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9
Q

Viridans summary

A

Long chains
Alpha haem
Not typable by lancefield

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10
Q

Pneumococci summary

A

Pairs
Alpha haem
Not typable by lancefield

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11
Q

Enterococci summary

A

Short chain
Any haem
D grp lancefield

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12
Q

Lancefield process

A

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

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13
Q

Human strep

A

Pyogenes (A)

Agalactiae (B)

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14
Q

Canine strep

A

Canis (G)

Pneumoniae (NT)

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15
Q

Equine strep

A

Equi
Equisimilis
Zooepidemicus
All C

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16
Q

Cattle strep

A

Zooepidemicus (C)
Agalactiae (B)
Dysgalactiae (C)
Uberis (NT)

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17
Q

Pig strep

A

Suis (D)

Porcinus (E)

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18
Q

Strep equi

A

C
Obligate parasite
Not commensal but can be ‘carried’ in tonsils and guttural pouch asympt
Cause strangles

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19
Q

Strangles symptoms early

A

Abrupt fever 103+ degrees c
Pharyngitis causing dysphagia neck extended listless depressed reluctant to eat
Pharyngitis laryngitis rhinitis may contrib to nasal discharge

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20
Q

Later strangles symptoms

A

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

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21
Q

What is strangles

A

Highly contagious resp disease affecting horses under 5 potentially fatal
Causes major farm disruption and there is widespread distribution
Suppurative pharyngitis and lymphadentis

22
Q

How are zooepidemicus and equisimilis differ from equi

A

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

23
Q

What is bastard strangles

A

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

24
Q

Strangles pathogenesis

A

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

25
Q

How do bact protect themselves from opsonisation

A

M pro and capsule and cause host cell lusis by secr streptolysinsnakd othe EC enz

26
Q

Virulence factor: peptidoglycan

A

Chemotactic for PMNs and pyrogenic

27
Q

Virulence factor: fibronectin binding pros

A

Involved in cellular invasion

28
Q

Virulence factor: M pro and M like pro

A

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

29
Q

Virulence factor: ZAG pro

A

Bind Ab Fc part

30
Q

Virulence factor: capsule

A

Protect against phagocytosis

Weakly immunogenic

31
Q

Virulence factor: C5a peptidase

A

Cleave C5a

32
Q

Virulence factor: hyaluronidase NADase and streptokinase

A

H: facilitate spreading in tissues
S: break down fibrin clots
N: inhib PMN activity and is leukocidal

33
Q

Virulence factor: SLO and SLS

A

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

34
Q

Virulence factor: superoxide dismutase

A

Neutralise antibac O2 free radicals prod

35
Q

Virulence factor: degradative enz

A

Release nutrients from host

36
Q

Virulence factor: strep pyrogenic exotoxins

A

Prod by some strains
Mainly grp A
Superantigens so are highly pro inflam and immunomodulatory

37
Q

Strangles diagnosis

A

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

38
Q

Strangles epidemiology

A

Purulent discharge
Horse-horse contact
Indirect transmission
Carriers

39
Q

Strangles treatment

A

Penicillin, most are resistant to eg ampicillin

Not always effective

40
Q

Immunity after natural strangles infection

A

75% dev over 5yr long imm

So a giid vacc should be feasible

41
Q

Vacc possibilities

A

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

42
Q

Control during strangles outbreak

A

Stop horse movement in and out
Quarantine
Antibio treatment

43
Q

Control of strangles after clinical recovery

A

Over 3 swabs at 1 wk intervals
Quarantine
Strict hygiene introduced

44
Q

Strep mastitis caused by

A

Grp A aka Pyogenes mainly in humans

Other grps more predom in animals

45
Q

Mastitis by agalactiae

A

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

46
Q

Mastitis by dysgalactiae

A

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

47
Q

Mastitis by uberis and parauberis

A

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

48
Q

Strep suis

A

Endemic in pig industry
Usually asympt can cause septicaemia meningutis pneumonia and arthritis
Young pigs most at risk

49
Q

Strep suis predisposing factors

A

Poor housing with inadeq ventilation

Esp if under intensive conditions that can cause stress leading to imm suppr

50
Q

Strep suis in humans

A

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

Bacteriology (15 decks)

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