streptococci Flashcards
-Streptococci represent a diverse group of gram — organisms
- many normally colonise — membrane
1- prodominent component of ——
2- many of —- virulence
3- However may also invade normally sterile body sites, causing significant —-
- positive
- mucosal
- respiratory, gastrointestinal
and genital tract - low
- disease
streptococci : basic lab features:
1- they are gram – shaped — can either be: —- tr —-
2- Optimal growth media
supplemented with —-
- may cause —- on blood agar
3- catalase is —
4- most are —–
- positive
-cocci - can be chains either long or short or pair ( diplococci )
- blood
- haemolytic ( destruction of rbc )
- negative
- facultative anaerobes
(Some are strict (obligate) anaerobes)
classification of systems:
1- based of their actions on —–
2- based on — contained in their cell wall
3- —- classification based on emm gene ( codes for m protein )
- blood containing agar ( haemolytic )
- antigen ( lance field classification )
- molecular ( new)
true or false:
Some clinically important streptococci often referred to by both Lancefield group and haemolysis patter
true
streptococci:
—- : Reduce Hb and cause a greenish discolouration of blood agar
—- : Lyse blood cells & cause complete clearing of blood agar in the vicinity of their growth
—- : no change in blood agar
- alpha haemolytic
- beta haemolytic
- gamma haemolytic
lancefield classification is a — system of grouping streptococci based on specific —- present in their cell wall
groups — of most clinical siginifance
basis of tests:
- serological
- antigen
- A-G
- antibody/anitgen reaction , positive if angulation is detected
clinically important streptococci :
- Strep. pyogenes (Group A, beta-haemolytic)
- Strep. agalactiae (Group B, beta haemolytic)
- Other beta-haemolytic streptococci
- alpha-haemolytic streptococci
-“viridans” streptococci
- Strep. pneumoniae (pneumococcus) - Enterococci (Group D, beta or non-haemolytic)
- Peptostreptococcus (anaerobic or non-haemolytic)
-STREPTOCOCCUS PYOGENES are group — and — haemolytic streptococci
- commonly colonise — of children and young adults ( colonisation is —- , influenced by —- and competition from other — in orpharynx)
- among the — prevalent pf human bacterial pathogen
- major cause of:
- A
- beta
- propharnyx
- transients
- immunity
- organics
- most
- bacterial pharyngitis
( in Irish epidemiology the invasive group A strep is notifiable disease )
GROUP A, beta HAEMOLYTIC STREPTOCOCCI: VIRULENCE MECHANISMS
- virulence factors include
1- — components :
—- : resists pahogystocis
—- : peptidoglycan can activate alternative complement system
2- — proteins :
->80 types, mediate attachment to cells, anti-phagocytic
- Major virulence factors – some types associated with greater severity of disease
-the M-like proteins bind —-
3- —- :
* Streptolysin O/S
exotoxins
– ASOT titre
* Hyaluronidase
– Tissue destruction,
allowing spread of
infection
* Leucocidin
* Haemolysins
* Streptokinase
4- —— erthyrogenic exotoxins
- responsible for fever and rash
- protent activators of — ( toxic shock syndrome )
- activate of — to increase secretion of —-
- produced by — and —
- structural
- capsule
- cell wall
- m protein
- IgG/igM
- cytolysins
- pyrogenic
- immune system
- T cells
- pro inflammatory cytokines
- antigen presenting cells and t lymphocytes
( check slide 13 for summary )
clinical infections include :
1- suppuartive infection as:
2- post infectious immune mediated complication as:
- supportive :
1. Pharyngitis
2. Scarlet fever
3. Erysipelas, cellulitis, necrotising fasciitis
4. Toxic shock syndrome, bloodstream infection - post - infectious :
– Rheumatic fever* - May later develop rheumatic heart disease
– Glomerulonephritis
- STREPTOCOCCAL PHARYNGITIS:
1- One of the most common bacterial infections of —-
2- occasionally due to group —-or —
3- spread: —- and its facilitated by —
4- incubation period:
5- history:
- childhood
- c or g
- Person-to-person via droplets (saliva ornasal secretions)
- Facilitated by overcrowding
- 2-4 days
- sore throat , headaches , fever , nausea , vomiting especially in children
( on examination: - Redness, oedema,
lymphoid hyperplasia - Enlarged tonsils with
exudate, enlarged
tender lymph nodes - Fever
lab findings: - positive throat culture
- immunological
(antibody) response
(anti-streptolysin O
titre, ASOT)
Hyperaemic, enlarged tonsils
with exudate
complication of STREPTOCOCCAL PHARYNGITIS:
1- suppurative complication:
2- non suppurative (immunoligcal sequele) :
- main reason for antibiotic treatment is to —-
- suppurative:
– Quinsy – peritonsillar abscess
– Otitis media
– Acute mastoiditis - non- suppurative :
– Acute glomerulonephritis
– Acute rheumatic fever - to prevent rheumatic fever
Delayed-type skin reactivity to pyrogenic toxin produced by the
organism —–
—– may also occur following impetigo
- scarletina ( from scarlet fever )
- pharungitis + fever
- Impetigo
- Erysipelas
- Cellulitis
- Necrotising fasciitis
are all under —-
skin and soft tissue infection
other serious infection include;
1- streptococcal toxic shock sydrnom which causes inflammation in — followed by —-
- causes production of —
- progresses —-
2- —- infection and mortality reaches —
- soft tissue inflammation
- followed by pain fever , chills , multi organ failure
- pyrogenic exotoxin
- rapidly
- blood stream
- 40%
complication : RHEUMATIC
FEVER & GLOMERULONEPHRITIS
Post-streptococcal auto-immune complications
* Affect a minority of people who have group A streptococcal infection
* Immune reaction: Development of antibodies to some fraction of the organism
– In rheumatic fever: the antibodies cross-react with cardiac tissue → immune complex deposition on the heart
– In post-streptococcal glomerulonephritis: immune
complexes are deposited on the glomerular basement
membrane
– Molecular mimicry
acute rheunaric fever is associated w — but not —-
- occurs —- weeks later
- symomts include:
-with recover , affected heart valves become —–
- —- required if undergoing procedure
that may put patient at risk of endocarditis
- Diagnosis is based on the ——
- streptococcal pharyngitis
- streptococcal skin infections
- 203 weeks
- joint pain , fever , carditis , may also get neurological involvement (Syndenham’s chorea)
- thickened and deformed
- Antibiotic prophylaxis
- jones criteria
acute glomerulonephritis is associated w —- and sometimes with —-
- causes:
- —-
- majority of young patients recover —- but may lead to:
-streptococcal pharyngitis
-streptococcal skin infections
- oedema , puffy face , swollen extremities due to sodium and water retention
- hypertension w albumin and blood in urine
- competly may lead to:
* However, may lead to permanent renal damage
* May warrant lifelong dialysis or renal transplantation
* Or may be fatal
STREPTOCOCCUS AGALACTIAE:
- in group —
- – haemolytic streptococci
- colonises the — and —
- —– % women intermittent carry S. agalactiae in vagina
- may be carried in —-
- important cause of neonatal sepsis:
- b
- b
- lower gi and gu tract
- 10-40%
- throat
- Neonatal colonization usually occurs via the mother’s
genital tract - Risk factors:
- Maternal colonisation
- Premature delivery / Premature rupture of membranes
- Prolonged labour
- Low birth rate
- Intra-partum fever
GROUP B -HAEMOLYTIC STREPTOCOCCI:
VIRULENCE MECHANISMS
1- —- polysacride:
- different — based on capsular polysaccharides
2- types —– most commonly associated w colonisation and disease
3- —-
4- —
5 — proteins as–
- capsule
- serotypes
- la, III, v
- haemolysins
- hyalurindase
- surface proteins - adhesins
other b-haemolytic streptococci :
- can cause similar disses as — but without —- complications
1- group c streptococci :
2- group g streptocci :
- group a
- immunilogical
- group c:
- Puerperal fever
- Tonsillitis
- Wound sepsis
- group g:
- Upper respiratory tract infections
- Endocarditis
A.“viridans” streptococci
B. Streptococcus pneumoniae
(‘pneumococcus’)
are both under —-
alpha-HAEMOLYTIC STREPTOCOCCI
viridian streptococci:
1- are found in —
2- most lack — exception for s.bovis in group d
3- clinical infection includes several associations with —- and —
- and its invasive disease often related to breech in —
- — and —- are the commonest viridian strep has — and infective —-
4- —- for dental caries
5- — purulent infections as brain and liver abscesses
5- — linked to colon cancer and infective endocarditis
- Oropharynx, GIT & GU
tract - lance field antigens
- associated w dental caries and endocarditis
- mussel surfaces
- strep sangus and strep mitis
-tooth biofilm - infective endocaditis
- strep mutans
- strep. angiosus ( milleri )
- strep bovis
-s peneumiua is type of — haemolytic and gram – in the shape of – in chains or dipoloccocci
- carried in — by :
1—– of healthy adults
2- —- of healthy children
- it has a —- of more than 90 serotypes and – available against some serotypes
- variety of clincial infections
-alpha
- +ve
-cocci
- nasopharynx
- 5-10%
-20-40%
- vaccines
(info: Gram-positive diplococci, i.e.
Pneumococcus
(Humphreys, Willatts & Vincent)
CHEKC SLIDE 32 SOOO IMPORTANT )
pneumococcal pneumonia:
- symptoms include:
- classically —> — pneumonia and may cause — especially in elderly
- complication include :
- —- a major predisposing factor
- Symptoms:
- Pleuritic chest pain
- Shortness of breath
- Purulent sputum
- classically —> lobar
- may cause bronchopneumonia
- Complications:
- Parapneumonic effusion
- Empyema / Lung abscess
- Bacteraemia
- influenza
—- is a common
cause of acute infection of the
paranasal sinuses and ear and it usually preceded by —- infection
- otitis media usually affects —
- sinusitis affects —
s.peneumoniae
- upper respiratory tract infection
- young children
- all ages
-how does meningitis get to the central nervous system ?
1- during a —
2- —– infection
3- —- infection
4- after —-
- the BSI/bacteramia 25-30% of patients w —— and it may accompany — it — occurs w cases of sinusitis or otitis media
- bacteriemia
- chronic ear
-sinus - after head
- penumococcal pneumonia
- meningitis
- rarely
enterococci:
1- has — species and —- and — are the most common
2- they are previously classified as —
3- —– usually low virulence
4- are facultative —-
5- their hemolytic patterns —
6- grow in the presence of —
7- — resistance is common
-18
- E. faecium and E facecalis
- group d streptococci
- bowel flora
- anaerobes
- varies ( alpha or beta)
- bile salts ( grow on macconket agar)
- vancomycin
CHECK SLIDE 37 SOOSOSOSO IMPORTANT
1-The at risk patients of enterococci infections are:
2- type of infections include :
At-Risk Patients:
* Recent surgery
* Underlying disease
* Malignancy
* Burns or trauma
* Recent antibiotics
* cephalosporins or
aminoglycosides
* Prolonged hospitalization
* Especially ICU
Types of infection:
1. Urinary tract infection
a) Particularly urinary
catheter-related
2. Endocarditis
3. Bloodstream infection
4. Wound infections
5. Intra-abdominal
infections
infective endocarditis has — flow through heart provides a surface for – to attach , this – enters blood usually after — that damages —- example:
- the bacteria attach to —– and —- form
- turbulent
- bacteria
- bacteria
- procedure
- epithelial barriers as dental extraction, cystoscopy
- valces and vegetations
(info: Vegetation on heart valve
(Slide: A Colour Atlas of Infectious
Diseases, Emond)
- anaerobic streptoccos peptostrepcoccosu:
1- more than 25% of anaerobes from —-
2- colonises —
3- infection include:
- clinical specimen
- oral cavity , GI , GU tracts , and skin
- infections include :
- Aspiration pneumonia
- Sinusitis and brain abscess
- Intra-abdominal abscesses
- Pelvic infections
diagnosis of infection that applies to any infection :
1- —- based on clinical features
2- – sent to a lab based on – of infection as:
3-in the lab:
- — on sterile site sample ( blood , csf , pus)
- culture takes —-
- samples incubated —– and —
- —– for hemolysis
- —– for eneterocci
- clinical suspicion
- appropriate samples based on site as:
– Blood (if invasive disease suspected)
– CSF (meningitis)
– Urine
– Throat swab (pharyngitis) - gram stain
- 24-48 hours
- aerobically and anaerobically
- blood agar
- macConkey agar
laboratory diagnosis includes:
- Identification
- Lancefield Grouping
- Bacitracin susceptibility (GAS)
- Optochin sensitive (pneumococcus)
- Bile solubility (enterococci)
- Serology
- Detect recent Group A infection in suspected rheumatic
fever & glomerulonephritis i.e. ASO titres (ASOT) - PCR
- Blood, CSF
- Urinary antigen (for pneumococcus)
s.pyogenes lab diagnosis:
1- its gram —- shaped – in —
2- — haemolytic
3- catalase is —
4- group –
-
-+ve
-cocci
- chains
- b
- negative
- a
( info : Group A ß-haemolytic streptococci showing bacitracin
susceptibility (clearing around bacitracin disc)
s.penumoniae lab diagnosis:
2- gram — shaped — in – or —-
3- – hameolytic
- catalase is —
- postive
- cocci
-chains or diplococci - alpha
- -ve
(Susceptible to optochin i.e. growth inhibited by optochin)
antibiotic resistance in penomocpcci Pneumococci :
can alter the structure of —— that are found on their surface
- —– as — cant bind to the penomococci and destroy their cell wall
- have different levels/degree of resistance which can be high/full level resistance or low/imtermediate level resistance
- its important to know if patient has been in area where there is — of resistance
- penicillin-binding proteins (PBPs)
- b lactam antibiotics
- as penicillin
- high resistance
streptococci: antibiotic treatment :
most commonly use —– :
1- penicillin which is nearly all — susceptible
2- cephalosporin used for :
- —— penomococci
- used for treatment of:
- used if — with —
- don’t use for —-
3- vancomycin used for:
- if —-
- if —
- cell wall active agents
- b-hamelytic strepcocci
- pencilin resistant
-mengitis - ceftriaxone 3rd gen - rash w penicillin
- don’t use for enterococci ( are intrinsically resistant )
- if b- lactam analphylix
- of resistant to b lactam suspected
enterococci antibiotic treatment:
1-* First line treatment for enterococci is — and id resistant to this which many e.faecium are then —
2-However VRE (vancomycin resistant enterococci) are — so we cant use vancomycin so patient mat become —- and +/- develop significant — due to VRE
3- – treatment options with significant potential — and — : —
- amoxilixllin
- vancomycin
- problematic
- colonised
- infection
- limited
- linezoilid
prevention and control vaccination :
- Pneumococcal vaccine
available against some
serotypes - 2 types of vaccine available
– PPV 23 – only used if >2 yrs,
recommended for >65 yrs of
age
– PCV 13 – Immunogenic from
6/52 of age, part of childhood
vaccination schedule, given at
2, 6 and 13 months - At risk groups should also be
offered vaccination
principle of infection and prevention :
-group a step :
- notable diseases :
- isolate in a single room if iGAS
confirmed until 24 hours on appropriate antimicrobial
therapy - public health
