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Staphylococcus-StreptococcusEnterococcus
Gr + cocci
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~ 21 genera
Common features
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Spherical shape
Gram stain reaction
Absence of endospores
Catalase activity
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Catalase positive genera
subdividing
Staphylococcus
Micrococcus
Stomatococcus
Alloiococcus
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Catalase negative genera
Streptococcus
Enterococcus
Staphylococcus
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Gram positive
Grow pattern
cluster of grapes
single cells, pairs,
short chains
Nonmotile
Aerobic or facultatively anaerobic
Catalase-positive
Grow in 10 % NaCl medium @ 18-40 o C
Most common Staph. causing diseases
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S. aureus
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S. epidermidis
S. saprophyticus
S. capitis
S. haemolyticus
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Produce coagulase
Coagulase negative
staphylococcus
Micrococcus
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Can be confused with CN staphs
Differ in that, they grow only aerobically
Resistant to lizostafin and furazolidone
Isolation of micrococcus in clinical samples
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Contamination ?
Stomatococcus
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Stomatococcus
mucilaginosus
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Only species in this
genus
Infection in the
immunocompromised
host
Alloiococcus
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Alloiococcus otitidis
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Only species in this
genus
Aerobic Gr +
Disease??
Staphylococcus and their diseases
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S. aureus
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Toxin-mediated
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Food poisoning
Toxic shock syndrome, scalded skin
syndrome
Cutaneous
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Impetigo
Folliculitis
Furuncles
Carbuncles, wound infections
Staphylococcus and their diseases
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S. aureus
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Others
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Bacteremia
Endocarditis,
Pneumoniae
Empyema
Osteomyelitis
Septic arthritis
Staphylococcus and their diseases
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S. epidermidis
Bacteremia
 Endocarditis,
 Surgical wounds
 Urinary tract infections
 Opportunistic infections of catheters,
shunts, prostetic devices and peritoneal
dialysates
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Staphylococcus and their diseases
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S. saprophyticus
Urinary tract infections
 Opportunistic infections
 Resistant to novobiocin
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Staphylococcus/physiology & structure
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Capsule
Peptidoglycan
Teichoic acids
Protein A
Coagulase and other sutface proteins
Cytoplasmic membrane
Staphylococcus/capsule
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Loose-fitting
Polysaccharide layer (slime layer)
In vitro
rare
Staphylococcus/peptidoglycan
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Half of the cell wall
More rigide compared to Gr negatives
Endotoxin-like activity
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Endogenous pyrogenes
Activation of complement
Production of int-1 from monocytes
Aggregation of polymorphonuclears
Staphylococcus/teichoic acids
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Teichoic & lipoteichoic acid
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Polysaccharide A in S. aureus
Polysaccharide B in S. epidermidis
Mediate the attachment of staphs to
mucosal surfaces
Poor immunogens (except when bound to
peptidoglycan)
Staphylococcus/protein A
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The surface of most S. aureus is coated with
protein A (not CNS)
Affinity to bind Fc receptor of IgG1, IgG2 &
IgG4
prevents the antibodymediated immune clearence of the bacteria
Staphylococcus/coagulase & other surface
proteins
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S. aureus clumping factor (bound
coagulase)
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Collagen-binding protein
Elastin-binding protein
Fibronectin-binding protein
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adherence to
host tissues
Staphylococcus/pathogenesis & immunity
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Toxins
&
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Enzymes
Staphylococcus/toxins
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Alpha toxin
Beta toxin
Delta toxin
Gamma toxin & Panton-Valentine Leukocidin
Exfoliative toxins
Enterotoxins
Toxic shock syndrome toxin-1
Staphylococcus/toxins
a Toxin
important mediator of tissue
damage in staphylococcal
diseases
toxic for many cells (erythrocytes,
leukocytes, hepatocytes,..)
produced by most strains of
S. aureus
Staphylococcus/toxins
b Toxin
sphingomyelinase C
toxic for many cells
role in tissue destruction &
abscess formation
produced by most strains of
S. aureus
Staphylococcus/toxins
d Toxin
wide spectrum of cytolytic
activity
detergent-like activity
produced by most strains of
S. aureus
Staphylococcus/toxins
g Toxin & Panton-Valentine Leukocidin
composed of two polypeptide
chains
toxic for many cells
Staphylococcus/toxins
Exfoliative toxins
staphylococcal scalded
skin syndrome (SSSS)
exfoliative dermatitis
two types: ETA & ETB
produced by 5 to 10 %
of all S. aureus strains
Staphylococcus/toxins
Enterotoxins
8 serologically distinct
enterotoxins exist (A-E, G-I)
stable to heating
resistant to
gastric & jejunal enzymes
produced by 30 to 50 %
of all S. aureus strains
are superantigens
Staphylococcus/toxins
Toxic shock syndrome toxin-1
heat & proteolysis resistant
all S. aureus responsible for
menstruation-associated TSS produce
TSST-1
50 % of the strains responsible for other
forms of TSS produce TSST-1
superantigens
Staphylococcus/enzymes
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Coagulase
Catalase
Hyaluronidase
Fibrinolysin
Lipases
Nuclease
Penicillinase
Staphylococcus/enzymes
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Coagulase
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S. aureus
2 forms
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Bound
free
Staphylococcus/enzymes
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Catalase
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“All staphylococci produce catalase”
H2O2 (toxic)
H2O
O2
Staphylococcus/enzymes
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Hyaluronidase
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Hydrolyzes hyaluronic acids
facilitates the
spread of S.
aureus in tissues
> 90 % of S. aureus produce hyaluronidas
e
Staphylococcus/enzymes
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Fibrinolysine
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Staphylokinase
All S. aureus
Dissolve fibrine clots
Staphylococcus/enzymes
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Lipases
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Nuclease
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All S. aureus & 30 % of the CNS produce several
different lipases
A marker for S. aureus
Penicillinase (b-lactamase)
Staphylococcus/IDENTIFICATION
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Microscopy
Culture:
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Nutritionally enriched agar media with sheep blood
Selective agar media for S. aureus with 7.5 % NaCl +
mannitol
Aerobic and anaerobic
Large, smooth colonies
Identification
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Positive coagulase, heat-stable nuclease, alkaline
phosphatase, mannitol ferment.
S. aureus
Streptococcus
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Gram positive
Grow pattern
pairs, chains
Most species are facultatively anaerobes
Some grow only in atmosphere enhanced
with CO2
Nutritional requirements are complex
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Blood, serum
“Catalase-negative”
Streptococcus
Classification is complicated
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1.
2.
3.
3 different schemes are used
Lancefield groupings according to serologic
properties (A-H, K-M, O-V)
Hemolytic patterns: b, a & g hemolysis
Biochemical properties
Streptococci and their diseases
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S. pyogenes (group
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A)
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Pharyngitis,
scarlet fever,
pyoderma,
erysipelas,
cellulitis,
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necrotizing
fasciitis,
streptococcal toxic
shock syndrome,
bacteremia,
rheumatic fever,
glomerulonephritis
Streptococci and their diseases
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S. agalactiae
(group B)
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Neonatal
infections
(meningitis,
pneumoniae,
bacteremia)
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Urinary tract
infections
Amnionitis,
Endometritis
Wound infections
Streptococcus pyogenes/physiology & structure
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Spherical cocci
Form short (clinical specimen) or long chains
(liquid media)
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Grow on enriched blood agar media
White colonies
1-2 mm with large zones
of b-hemolysis
Encapsulated strains mucoid
Basic structure in the cell wall is
peptidoglycan as Staphs
group spec. Ag
Streptococcus pyogenes/physiology & structure
Group specific carbohydrate
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Within the cell wall
10 % of the dry weight
Is used to classify group A streptococci and
distinguish them from others
Streptococcus pyogenes/physiology & structure
Type specific proteins
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M protein
major type-specific protein
associated with virulent streptococci
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2 polypeptide chains
1.
2.
Highly conserved among all ggroup A streptococci
Responsible for the antigenic variability
>80 serotypes
T protein (trypsin-resistant)
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secondary
Usefull when bacteria fail to express the M protein
Streptococcus pyogenes/physiology & structure
Other cell surface components
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M-like proteins
Lipoteichoic acid
F protein
Capsule (hyaluronic acid)
Streptococcus pyogenes/Pathogenesis&Immunity
Virulence of S. pyogenes
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The ability of the bacteria
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to adhere to the surface of the host cells
Invade into the epithelial cells
Avoid opsonization & phagocytosis
Produce a variety of toxins & enzymes
Streptococcus pyogenes/Pathogenesis&Immunity
Pyrogenic exotoxins
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(Streptococcal pyrogenic exotoxin, Spes)
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Produced by lysogenic strains
Superantigens
Responsible for the streptococcal toxic
shock syndrome
Streptococcus pyogenes/Pathogenesis&Immunity
Streptolysin S & O
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Streptolysine S
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Streptolysine O
lyse erythrocytes
leukocytes
platelets
responsible for b-hem.
lyse erythrocytes
leukocytes
platelets
antibodies are formed
against
ASO test
Streptococcus pyogenes/Pathogenesis&Immunity
Streptokinases
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Deoxyribonucleases
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A&B
Lyse blood clots
Used in medicine
A to D
Depolymerase free DNA in pus
viscosity
reduce
C5a peptidase
Hyaluronidase,diphosphopyridine nucleotidase
Streptococcus pyogenes/IDENTIFICATION
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Microscopy
Culture:
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Proper collection of throat swab specimen
Nutritionally enriched agar media with sheep
blood
Selective media (media with “bactrim”)
Identification
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Table 23-4
Streptococcus agalactiae (Group B)
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The only species that carries the group B
antigen
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physiology & structure
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Gr + cocci
Short or long chains (indistinguishable from S. pyogenes)
Buttery colonies, narrow zone of b-hem.
Subdividing
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The B antigen
group specific
Capsular polysaccharides
type-specific
C protein (surface protein)
Streptococcus agalactiae/IDENTIFICATION
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Microscopy
Culture:
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Readily grow on a nutritionally enriched medium
Large colonies
b-hemolysis may be absent
selective broth
medium with antibiotics
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Identification
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Preliminary identification
(+) CAMP test,
hydrolysis of
hippurate
Other beta-hemolytic streptococci
Group C, F and G are most commonly
associated with human disease
2 species of particular importance
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S. anginosus
S. dysgalactiae
Viridans Streptococci
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a-hemolytic and nonhemolytic streptococci
Produce green pigment on blood agar media
Require complex media supplemented with
blood products and inc. @ 5-10 % CO2 atmsp.
Streptococcus pneumoniae
Encapsulated, Gr + coccus
Lancet-shaped cells, in pairs or short chains
a-hemolytic
Can grow only on enriched media (with blood
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products)
Catalase (-)
Capsule, classified accr. to polysaccharides
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90 serotypes
Capsular polysaccharides are used in vaccines
Teichoic acid
C polysaccharide (CRP)
S. pneumoniae / diseases
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Pneumoniae
Meningitis
Sinusitis
Otitis media
Bacteremia
Streptococcus pneumoniae/Pathogenesis&Immunity
The disease manifestations are caused primarily
by the host response to infection
Streptococcus pneumoniae/Pathogenesis&Immunity
Colonization & migration
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S.pn colonizes the oropharynx
Can spread to the lungs, paranasal
sinuses, middle ear, blood stream
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By means of:
Surface protein adhesins, secretory IgA
(sIgA) protease, pneumolysin
Streptococcus pneumoniae/Pathogenesis&Immunity
Tissue destruction
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Mobilization of inflamatory cells
pneumococcal infections
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characteristic of
Teichoic acid
Peptidoglycan fragments
Pneumolysin
H2O2 production
Phosphorylcholin
Phagocytic survival
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Capsule
Pneumolysin mediated suppression of the
phagocytosis
Streptococcus pneumoniae/IDENTIFICATION
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Microscopy
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Culture:
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Lancet-shaped, Gr (+) diplococci, unstained
capsule (Gram stain with “quellung” reaction)
Enriched supplemented medium with blood
Selective medium with gentamicin
Identification
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Bile solubility test
Optochin
Enterococcus
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Most frequently isolated & most commonly
responsible for human disease with
streptococcus among gram-positive cocci
“enteric cocci”
Possess the group D cell wall antigen
16 species in the genus
E. faecalis & E. faecium are most commonly
isolated
Enterococcus/physiology & structure
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They can not be differentiated from S.
pneumoniae in microscope
Facultatively anaerobic
Optimal growth temp.= 35 oC (10oC to 45oC)
White, large colonies on blood agar (after 24h)
Nonhemolytic (or a or b-hemolysis)
Grow in the presence of
 6.5 % NaCl, tolerate 40 % bile salts,
hydrolyse esculin
Enterococcus/Pathogenesis&Immunity
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Are commensal with
limited potential for
causing disease
Do not possess toxins
Cannot avoid being
engulfed & killed by
phagocytic cells
BUT,
Cause
Serious
Disease
Enterococcus/Pathogenesis&Immunity
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Virulence factors
Adhesive factors
 Bacteriocins
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Inherently resistant to many
antibiotics
Enterococcus/Clinical Diseases
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Can cause life-threatening infections
One of the most feared nosocomial
pathogens
10% of all nos. infct.
Most commonly involved sites
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Urinary tract
Blood stream
A sever complication: endocarditis( following
bacteremia)
Enterococcus/Laboratory diagnosis
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Grow readily on nonselective media
Resemble S. pneum.
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Differentiation
resistant to optochin
don’t dissolve when
exposed to bile
hydrolyze PYR
pyrolidonyl-b-naphthylamide