Streptococcus pyogenes (group A β-hemolytic Streptococcus (GABHS)) is the common cause of acute bacterial pharyngitis also known as strep throat or sore throat. Recorded cases of GAS bacterial pharyngitis are 15-36% in children and 5-15% in adults. School aged children in seasons of spring and winter harbor the bacterium up to 20% whereas this rate is much lower in adults. On a global scale, over 616 million new cases of GAS pharyngitis occur every year. Not only is this bacterium responsible for hundred millions of pharyngitis cases but also approximately 10,000 to 15,000 cases of invasive GAS cases are reported annually in the United States, accounting for 10% to 13% mortality rate (http://www.cdc.gov/ncidod/dbmd/abcs/forinvasiveandnoninvasivediseaseincidence). Acute infections can lead to rheumatic fever and post-streptococcal glomerulonephritis (kidney inflammation), which distress children worldwide with disability and death, if antibiotic treatment fails or if the disease is left unattended. Rheumatic fever and rheumatic heart disease are known to be the leading causes of cardiovascular death during the first five decades of life in underdeveloped countries mainly concerning children. Tissues contributing to the GAS nosocomial infections are upper respiratory tract, skin, vaginal and anal area, although latter cases are rare.
GAS has several surface proteins and produces numerous extracellular products that facilitate permeation and successive evasion of the host’s immune system. Streptococcal pharyngitis results from the proliferation of GAS in the pharynx. Virulence associated factors enable S. pyogenes to attach to host tissues, elude the immune response, and spread by penetrating the host tissue layers followed by colonization.
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S. pyogenes, its virulence, antibiotic, phytochemicals
1. 1
GAS
virulence
Soheila Abachi
For more information you could download my thesis at the following link
[https://dalspace.library.dal.ca/handle/10222/10559/browse?type=author&value=Abachi+
Hokmabadi%2C+Soheila]
2. 2
Cross-section of the two types of bacterial cell
walls
Department of crop and soil environmental sciences, Virginia Polytechnic
Institute and State University
Structure of the Gram-positive
cell wall Joubert, Quizlet LLC
Cell wall
3. 3
Colored trans- mission electron
micrograph of GAS, cell diameter of
one micron
Sport photo gallery website
Cell surface structure of GAS &
secreted products involved in its
virulence
Todar's online textbook of bacteriology
Bacterial surface
4. 4
Surface proteome of GAS
www.studyblue.com
Streptococcus colonization is facilitated by
Adherence
Signaling
Nutritional adaptation
Host modulation
Virulence
6. GAS virulence factors
6
Antiphagocytic
M protein
M-protein-like
• M-related protein (Mrp)
• Enn and others
Hyaluronic acid capsule
C5a peptidase (a protein fragment released from cleavage complement
component C5 by protease C5-convertase into C5a and C5b fragments)
Adherence to epithelial cells
Lipoteichoic acid (oral epithelial cells)
Fn binding proteins (oral epithelial, cutaneous
Langerhans cells)
M protein (skin keratinocytes)
Hyaluronic acid capsule (CD44-positive keratinocytes)
7. GAS virulence factors
7
Internalisation
M protein
Protein F1
Invasion
Hyaluronic acid capsule
M protein
Spread through tissues
Hyaluronidase
Streptokinase
SpeB (cysteine protease)
DNAses A-D
Systemic toxicity
Streptolysin O
Streptolysin S
Superantigenic exotoxin
9. Fn binding protein(s)
9
100 kDa, anchored to cell wall at its LPxTG domain in C-terminal
region of molecule
Environmentally regulated expression, expression of protein F1
enhanced in O2-rich environment & when GAS adhere to the
cutaneous surface
various Fn-binding proteins have different N-terminal domains
All contain a peptide that is repeated in tandem from three to five times
(R1, R2, etc)
GAS has 5 Fn binding protein(s) protein F1 (Sfb1), protein F2, PFBP,
SOF, & Sfbx
Utilize (i) peptide repeat domains to bind Fn (primarily to N-terminal
domain of Fn) & (ii) upper binding domain that reacts with collagen
binding domain of Fn e.g. F1 & F2 [such interactions promote efficient
entry of GAS into host cells]
Fn is large glycoprotein, 440 kDa, in human blood plasma &
extracellular matrix
10. 10 conformational change is a change in the shape of a macromolecule, often induced by
environmental factors
11. Quantification of primary adherence of different strains of S. pyogenes (serotypes M6 and
M49) and S. epidermidis (positive control) to uncoated polystyrene surfaces.
Cordula Lembke et al. Appl. Environ. Microbiol.
2006;72:2864-2875
13. FIG.2. Quantification of characteristic primary adhesion profiles of different S.
pyogenes serotype strains and S. epidermidis (positive control) to immobilized
matrix proteins and polystyrene surfaces. (A) Serotype M1 GAS strain; (B) serotype
M2 GAS strain; (C) serotype M6 GAS strain; (D) serotype M18 GAS strain; (E) S.
epidermidis (positive control strain). Bacteria were grown in BHI under static
conditions at 37°C in ambient air. Adhesion of the bacteria was quantified by
safranin staining of potential biofilms and subsequently by measuring absorbance at
492 nm at the indicated time points. The mean values of six independent
experiments and standard deviations are shown. Immobilized matrix proteins were
as follows: Fn, fibronectin; Fo, fibrinogen; Co I, collagen type I; Co IV; collagen
type IV; Lam, laminin; wPrt, without proteins (i.e., polystyrene surface).
15. 15
• ATP synthase regulates
intercellular & cytoplasmic pH
• Important molecular target for
drugs in the treatment of infectious
disease
ATP synthase schematic
University of Leeds, Faculty of Biological Sciences
16. ATPase, Acid tolerance, lack of
TCA cycle
16
Streptococci lack respiratory chains, relying on glycolysis or
arginine fermentation for production of ATP (energy)
GAS lacks necessary enzymes for functional TCA cycle &
oxidative-cytochromes for electron transport
Unable to generate a large proton potential
Cell membrane physiology major role in acid base regulation
Depend on permeability of cells to protons at various
environmental pH values
Membrane ATPase important in cell permeability
H+-ATPase (ATP synthase) hydrolyze ATP & form
electrochemical gradient of protons
GAS extrude protons across plasma membrane establishing
an electrochemical potential providing driving force for various
kinds of physiological work e.g. uptake of sugars, amino acids,
other nutrients with aid of secondary porters (primary transport
systems) & regulation of cytoplasmic pH & cytoplasmic
concentration of potassium & other ions
Cytochromes are hemeproteins containing heme groups and are primarily responsible for the
20. Scanning electron microscopy of S. pyogenes biofilm development under continuous flow
conditions in a flow chamber system.
Cordula Lembke et al. Appl. Environ. Microbiol.
2006;72:2864-2875
M1
8
M2
21. 21
Scanning electron microscopy of S.
pyogenes biofilm development under
continuous flow conditions in a flow
chamber system. (A to C) Serotype M18
GAS strain; (D to F) serotype M2 GAS
strain. Biofilms were formed for 72 h on
coverslips coated with collagen type IV (A
to C) or fibronectin (D to F) in a flow
chamber system under continuous flow
conditions for the medium. The
development of the biofilm architecture is
shown at magnifications of ×140 (D), ×350
(A), ×1,400 (B and E), and ×3,500 (C and
F).
22. SEM of S. pyogenes biofilms.
Cordula Lembke et al. Appl. Environ. Microbiol.
2006;72:2864-2875
M4
9
M6
M1
8
SEM of S. pyogenes biofilms. (A and B)
Serotype M49 GAS cells from a 72-h
static culture on an uncoated plastic
surface. Images reveal primary bacterial
adherence without subsequent formation
of typical biofilm structures, with
magnifications of ×500 (A) and ×5,000
(B). (C and D) Serotype M6 GAS
grown on plastic coverslips for 72 h
in static culture, with magnifications of
×500 (C) and ×5,000 (D). (E and F)
Biofilms of the serotype M18 GAS
strain grown for 72 h in static culture
on collagen type IV-coated coverslips,
with magnifications of ×200 (E) and
×2,000 (F).
23. Biofilm
23
3D biofilm structures consistof up to 46 bacterial layers
GAS mutants failed to form biofilm
lacking transcription for regulators Mga & CovR (CsrR)
lacking M protein, hyaluronic acid capsule
26. Biofilm, Adhesion
26
serotypes M1, M12, M28, M49 biofilm-negative strains
serotypes M1, M4, M12, M49 form microcolonies when
grown in liquid medium.
serotypes M1, M4, M12, M49 aggregation into
microcolonies mediated by conserved 19-amino-acid
residue peptide present in M protein & protein H
serotypes M2, M18 preferentially adhere to human
matrix protein-coated surfaces
serotype M6, M14 preferentially adhere to uncoated
plastic or glass surfaces
Isolate-specific patterns within a certain serotype could be
due to diverse regulatory mechanisms leading to
differential expression of primary adhesins.
The adhesins & corresponding regulators enabling strains
to directly interact with uncoated plastic are
uncharacterized
Protein H: a surface protein with separate binding sites for IgG, albumin
27. 27
Rheumatic fever M serotpyes 5, 6, 18, 19, 24, …
Acute post streptococcal glomerulonephritis M
serotpyes 12, 49, 55, 57, 60, 63, …
Pharyngitis causing M serotypes 1, 3, 5, 6, 12,
18, 19, 24,…
30. 30
Compound name Class Strain Conc. MOA
Ursolic acid
Oleanolic acid
Triterpene
acid
S. mutans
UA159
1024 µg/ml 100% AI
(-)-Epigallocatechin
(-)-Epigallocatechin-3-O-
gallate
Flavan-3-ol S.
pyogenes
DSM 2071
30 μg/ml 15-40% AI
Epicatechin-(4β→8,
2β→O→7)-epicatechin-
(4β→8)-epicatehin
Flavan-3-ol S. mutans
UA159
500 µg/ml 85% F-
ATP AI
Morin Flavonol S.
pyogenes
MGAS6180
225 μM 50-60 %
BR
AI; Adherence Inhibition, BR; Biofilm Biomass Reduction, F-ATPAI; F-ATPase
Activity Inhibition
Phytochemicals with anti-infective effects
against Streptococcus spp.
Zhou et al., 2013, Janecki et al., 2010, Duarte et al., 2006, Gregoire et al., 2007, Green et al., 2012, Prabu et al., 2006
33. 33
Penicillinase, a group
of -lactamase enzymes,
inactivates lactam ring of
penicillin molecule.
Erythromycin
resistant Target
modification,
methylation of 23S rRNA
Mechanisms of antibiotic
resistance in bacteria
Todar's online textbook of bacteriology
Leclercq et al. 2002
Antibiotic resistant
34. 34
Cross section of a biofilm with
attachment to surface
Antibiotic containing aqueous phase
Bacteria with activated stress responses
Antagonized antibiotic action in zones with nutrient depletion
Bacteria differentiated into a protected phenotype
Antibiotic resistant
Biofilms start forming:
1)Cellular recognition
of attachment sites on
surface
2)Nutritional cues
3)Expose of planktonic
to sub-MIC
antimicrobial
36. Resistance
36
Resistance mechanism
Prevent antibiotic from binding to target
Allow cells to grow at an elevated level of
antibiotic
Main types of resistance are
Target modification by mutation
Target modification by specialized enzymatic
changes
Target substitution, such as expressing an
alternative target
Antibiotic modification
Antibiotic efflux
Restricted antibiotic permeation
37. Resistance
37
Persister cells
Are not antibiotic-resistant mutants
Are slow dividing cells (dormants), little or no cell-wall synthesis,
translation or topoisomerase activity
Temporarily give up propagation in favor of survival
Able to survive a dose of antibiotic that kills regular cells
Numbers in a growing population of bacteria rises at mid-log &
reaches max. Of 1% at stationary phase
Are produced substantially in slow-growing biofilms
Form when proteins toxic to cell, growth & essential functions are
overproduced/over expressed
Resistance mechanisms prevent the antibiotic from
hitting/binding a target
Tolerance mechanism shutting down the targets
39. Quorum sensing
39
Quorum-sensing consist of three components,
a small soluble signal peptide
a two-component regulatory system that has a
membrane-bound histidine kinase sensor &
an intracellular response
40. Quorum sensing
40
Two-component regulatory system CsrRS (CovRS)
regulates its own expression & virulence-associated
genes;
has operon
streptokinase
cysteine protease SpeB
SLO
Mga activates its own transcription & several virulence
genes;
M protein family (emm, mrp, arp, enn)
C5a peptidase
serum opacity factor (sof; sbfII)
Sic
Collagen-like protein (sclA)
41. Quorum sensing
41
Rgg (or RofB) regulates expression of;
Genes encoding regulators Mga and CsrRS
FasBCA (three-component system) regulates
expression of;
Fibrinogen & fibronectin binding
SLS encoding locus (sagA)
SilA & SilB (two-component system) regulates
expression of;
Proteins responsible for spreading of S.
pyogenes into deeper tissues during infection
43. M protein
43
Primary virulence factor
Resist phagocytosis in blood &
Attach to host cells
Starts from surface of the bacteria
a-helical, coiled-coiled protein (advantage: antigenic variation,
multiple functional domains)
number & sequence of the A & B repeats vary depending upon M
type.
C-repeats conserved among different M types.
Adhesion to host cells mediated by either
variable domain or conserved domain depending upon the
receptors expressed by host cells
Close resemblance of its molecular design to certain mammalian
proteins formation of epitopes responsible for serological
cross-reactions between microbial & mammalian proteins
44. M protein
44
Expression of M protein enhanced at higher partial pressures of
CO2 & GAS adheres to deeper tissues where more likely to
encounter phagocytic cells
emm gene encodes M serotype specificity & M type-specific
opsonic epitopes
Adhesion by the variable domain depend upon type of M protein
expressed & on type of receptors expressed by the targeted
tissue
Pharyngitis causing M serotypes (1, 3, 5, 6, 12, 18, 19, 24,…)
46. Treatment
46
Treatment goals include
Prevention of suppurative and nonsuppurative
complications
Reduction of clinical signs and symptoms
Reduction of bacterial transmission
Minimization of antimicrobial adverse effects
Antibiotic selection requires consideration of
Patients’ allergies
Bacteriologic and clinical efficacy
Frequency of administration
Duration of therapy
Potential side effects
Compliance
Cost
49. Treatment failure
49
10-18% penicillin treatment failure
Total treatment failure as high as 30%
Non-compliance
50. Treatment failure
50
Treatment failure defined as
Detection of GABHS of same serotype, with or
without symptoms of pharyngitis, after recent
completion of appropriate antibiotic therapy
Mechanisms for treatment failures
reinfection through various means
lack of compliance
streptococcal tolerance to penicillin
early initiation of antibiotics resulting in inadequate
immune response
lack of protective microflora or its involuntary
eradication
copathogenicity of beta-lactamase-producing flora
52. Adhesion
52
6 different mechanisms of adhesion for S. pyogenes
Pharyngeal epithelial cells and HEp-2 cells M protein-mediated
adhesion
Tissue culture cells infected with influenza virus fibrinogen-
mediated adhesion
Bacterial attachment to different types of substrata with fatty
acid-binding domains
LTA mediated adhesion
Depend upon type of target
substratum used in assay
54. Capsule
54
GAS depend on HA capsule to evade
phagocytosis & to interact with epithelial cells
HA capsule only plays a secondary role in
infections caused by GAS strains pathogenic for
humans
Digest tissue HA & facilitate spread of GAS
4% of GAS and 2.7% of GCS positive HA
12.5% of GAS, 72.1% of GBS, 84% of GCS and
85.3% of GGS positive HY
55. 55
200 known M types divided into 4 major
subfamilies based on sequence of peptidoglycan-
spanning domain at the 3′ end of emm
Subfamilies A, B, C cause pharyngitis
Subfamily D cause skin diseases
Subfamily E generalists, cause symptomatic
infection at either tissue, skin or throat
57. Cell wall, division
57
Many virulence factors of G + anchored to PG by a
sorting signal
Signal sequence of M protein, which contains an
YSIRK-G/S motif (SP+YSIRK), is targeted to the division
septum, while signal sequence of protein F lacking
this motif (SP−YSIRK) is targeted to old pole
M protein is rapidly anchored at septum,
simultaneously at the mother & daughter septa
By contrast SP−YSIRK SfbI protein accumulates
gradually on peripheral PG resulting in a polar
distribution impairment of septum assembly results in
marked reduction in amount of M protein, but not of
SfbI
59. Hydrophobicity
59
Bacterial pathogens depend on hydrophobic interactions for
successful colonization of a host
M+ GAS possess more negative surface charge & express extreme
surface hydrophobic properties
Binding of fibrinogen & albumin decreased surface hydrophobicity of
M+ GAS
GAS clinical isolates hydrophobic
LTA release from cytoplasmic membrane, bind to surface proteins via
glycerol phosphate end, glycolipid end free to interact with various
substrata utilizing the hydrophobic effect
Sub-MIC penicillin reduces hydrophobicity less adhesion
GAS in Exponential phase much less hydrophobic than in stationary
phase
During exponential growth phase hyaluronate capsule cover LTA
hydrophobicity decrease
GAS cells enter stationary phase, capsule no longer produced in high
quantities & HY degrade polymer hydrophobicity increase
Major adhesin(s) of streptococci may be hydrophobins
Stationary phase GAS superior to exponential GAS in adhesion to
60. Hydrophobicity
60
Sub-MIC antibiotics decrease cell surface hydrophobicity
increase negative electric charge hinder interaction
between GAS & pharyngeal Epi cells suppression of
infection
Bacitracin & pristinamycin increased hydrophobicity no
effect on adhesion to pharyngeal Epi cells
Induces excretion of LTA from GAS loss of ability to adhere
61. Fimbriae
61
Type-specific M protein was removed from intact
surface GAS showed increased susceptibility
to phagocytosis, (b) lack of opsonic effect of
homologous M antibody on the treated
streptococci, and (c) loss of HCl- extractable M
protein.
GAS lacking M protein adhered to human oral
mucosal cells equally as well as untreated,
fimbriated organisms which retained their M
protein
Fatty acids ester linked with glycerol teichoic acid
(fimbriae) rather than M protein of streptococci
binds the organisms to epithelial cells
64. Structure-activity; phenolic acids
64
Greater antibacterial activity against gram-positive than negative (strain dependent activity)
OM of gram-negative bacteria with hydrophobic surface structure excludes hydrophilic
molecules, so are inherently resistant to AM including phenolic acids
Gram-positive enclosed in plasma membrane covered by thick peptidoglycan wall (No OM)
Poorly absorbed in small intestine, some stimulate growth of gut microbes
Structure-activity relationship
Different alkyl chain length with hydroxyl groups important for AM actions, longer chain better
activity
Presence of hydroxyl groups on phenol groups & oxidized status of phenol groups important
Disrupt fluidity of the cell membrane with increasing hydrophobic alkyl chains
Enter molecular structure of membrane with polar hydroxyl group oriented into aqueous
phase by hydrogen bonding & nonpolar carbon chain aligned into lipid phase by dispersion
forces, when hydrophilic force exceeds hydrophobic one, activity disappear
Number & position of substitutions in benzene ring & saturated side-chain length important
Potency against Lactobacillus spp.
1.benzoic acids; 4-hydroxy- > 3-hydroxy- > non-substituted > 4-hydroxy-3-methoxy- >
3,4-dihydroxy-substituted acids
2.phenylacetic acid: non-substituted > 3-hydroxy- > 4-hydroxy- > 3,4-dihydroxy-
substituted acids
3.phenylpropionic acids; non-substituted > 4-hydroxy- > 3-hydroxy > 3,4-dihydroxy-
substituted acids
65. Structure-activity; Flavonoids
65
Flavonoids; largest groups of secondary metabolites, constructed
basically with an A & C ring of benzo-1-pyran-4-quinone & a B ring,
commonly conjugated with sugars as glycosides
Main classes;
(1) flavones (basic structures), e.g. luteolin, apigenin, diosmetin,
chrysoeriol, tangeretin, sinensetin, gardenin, vitexin and baicalein;
(2) flavonols (having a hydroxyl group at the 3-position), e.g. kaempferol,
quercetin, galangin, datiscetin, morin, robinetin, isorhamnetin,
tamarixetin, quercetagetin and myricetin;
(3) flavanones (2–3 bond saturated), e.g. hesperetin, taxifolin, eriodictyol
and naringenin;
(4) flavan-3-ol, e.g. catechin and epicatechin;
(5) isoflavone, e.g. genistein, daidzein and coumestrol;
(6) anthocyanidins: cyanidin, delphinidin, pelargonidin and peonidin
Gram-positive absorb more EGCG into peptidoglycan cell wall &
aggregate its presence, while Gram-negative do not aggregate & absorb
less EGCG because of repulsive negative charge of lipopolysaccharides
on surfaces of Gram-negative, binding of EGCG to peptidoglycan disrupts
its function in osmotic protection, cell division, & cell wall biosynthesis
66. Structure-activity; Polyphenols
66
Phenolic acids (ellagic & gallic acids) or flavonoids (flavan-3-ol,
flavan-3-4-diol or flavan-4-ol) are esterified or polymerized into
dimeric, oligomeric or polymeric compounds
Most abundant are tannins; hydrolysable tannins (HT) &
condensed tannins (CT)
HT; complex molecules with a polyol as a central core such
as glucose, glucitol, quinic acids, quercitol and shikimic acid,
partially or totally esterified with a phenolic group, i.e. gallic
acid (3,4,5-trihydroxy benzoic acid; gallotannins) or gallic acid
dimmer hexahydroxydiphenic acid (ellagitannins)
CT (proanthocyanidins); polymers of flavan-3-ols (epi)catechin
& (epi)gallocatechin units, linked by C4-C8 and C4-C6
interflavonoid linkages
prodelphinidin B-2 3′-O-gallate (a proanthocyanidin gallate); anti-
HSV-2; inhibit attachment & penetration between cells & viruses
through instability of viral glycoproteins
Gallotannins; strong affinity for iron & inactivation of membrane-
bound proteins, morphological changes due to inhibition of cell
division by binding of gallotannins to cell wall or inhibition of
enzymes involved in cell separation
67. Phytochemicals Antibacterial
MOA
67
Phenols & phenolic acids; disruption of energy production
due to enzyme inhibition by oxidized products, through
reaction with sulfhydryl groups or through more nonspecific
interactions with proteins
flavonoids (robinetin, myricetin and epigallocatechin
gallate); inhibit the synthesis of nucleic acids of both Gram-
negative & positive, B ring may play a role in intercalation
or hydrogen bonding with stacking of nucleic acid bases
which cause inhibitory action on DNA and RNA synthesis
Quercetin; binds to GyrB subunit of E. coli DNA gyrase and
inhibits enzyme’s ATPase activity, cause an increase in
permeability of inner bacterial membrane & a corruption of
membrane potential
Epicatechin gallate & epigallocatechin gallate; inhibit
antibiotic efflux pumps in MRSA, inhibit β-ketoacyl-ACP
reductase (FabG) & trans-2-enoyl-ACP reductase (FabI)
components in bacterial type II fatty-acid synthase system
68. Phytochemicals Antibacterial MOA
68
Molecules that mimic AHL signals and affect
quorum-sensing
Inhibit AHL-dependent gene expression, interfere
with several AHL-regulated bacterial processes
without any effect on bacterial growth or general
protein synthesis capability
Inhibit interspecies coaggregation
Prevent adhesion, inactivate mature single & multi-
species biofilms, decrease polysaccharide
production
69. synergists/potentiators of
antibiotics
69
phytochemicals that have different antibacterial
modes of action can potentiate activity of same
antibiotic class. For instance, berberine (interact with
the cytoplasmic membrane and with DNA) &
epicatechin, epigallocatechin gallates (inhibit efflux
activity and bacterial type II fatty acid synthesis) have
distinct antibacterial mode of action, however, they
potentiate antibacterial action of β-lactam antibiotics
piperine, reserpine, & triterpenoid saponins sensitize
bacteria & potentiate action quinolones & polymyxins
(chemotherapeutic strategy; sensitize bacteria with
phytochemicals & modulate their susceptibility to
antibiotics at reduced concentrations)
phytochemicals with membrane permeability effects,
potentiate antibacterial activity of antibiotics that
target intracellular sites (aminoglycosides, macrolides,
quinolones, tetracyclines)
74. 74
Permissions P. Dirckx, Center for Biofilm Engineering, Montana State University, Bozeman
Development of new antimicrobial agents
75. 75
Handling the infections
less effective
low survival rate
long-term disability
Immuno-compromised
Demand: discovery of
natural compounds
with diverse chemical
structures,
mechanisms of
action
Threat
Threats
Quantification of primary adherence of different strains of S. pyogenes (serotypes M6 and M49) and S. epidermidis (positive control) to uncoated polystyrene surfaces. Bacteria were grown in BHI under static conditions at 37°C in ambient air. Adhesion of the bacteria was quantified by safranin staining of potential biofilms and subsequently by measuring absorbance at 492 nm at the indicated time points. The mean values of six independent experiments and standard deviations are shown.
Scanning electron microscopy of S. pyogenes biofilm development under continuous flow conditions in a flow chamber system. (A to C) Serotype M18 GAS strain; (D to F) serotype M2 GAS strain. Biofilms were formed for 72 h on coverslips coated with collagen type IV (A to C) or fibronectin (D to F) in a flow chamber system under continuous flow conditions for the medium. The development of the biofilm architecture is shown at magnifications of ×140 (D), ×350 (A), ×1,400 (B and E), and ×3,500 (C and F).
SEM of S. pyogenes biofilms. (A and B) Serotype M49 GAS cells from a 72-h static culture on an uncoated plastic surface. Images reveal primary bacterial adherence without subsequent formation of typical biofilm structures, with magnifications of ×500 (A) and ×5,000 (B). (C and D) Serotype M6 GAS grown on plastic coverslips for 72 h in static culture, with magnifications of ×500 (C) and ×5,000 (D). (E and F) Biofilms of the serotype M18 GAS strain grown for 72 h in static culture on collagen type IV-coated coverslips, with magnifications of ×200 (E) and ×2,000 (F).
![1
GAS
virulence
Soheila Abachi
For more information you could download my thesis at the following link
[https://dalspace.library.dal.ca/handle/10222/10559/browse?type=author&value=Abachi+
Hokmabadi%2C+Soheila]](https://image.slidesharecdn.com/s-160326221921/85/S-pyogenes-its-virulence-antibiotic-phytochemicals-1-320.jpg)
