SBL100
Saran
Lecture 4
Why is adherence important?
BIOFILM
Quorum Sensing
Why is adherence important?
Biofilms Formation
and Impact
• What triggers biofilm formation?
• Bacterial attachment to surfaces
• Nutritional depletion
• Sub-inhibitory concentration of
Antibiotics
• A critical population density of
bacteria.
Bacterial Capsule
• Some species of bacteria
have a third protective
covering made up of
polysaccharides called
capsule.
• Capsule mediate
adherence
• Helps evade host defenses
• It is identified using
negative staining method
such as India Ink Method.
Griffith’s Transformation Experiment
Bacterial Toxins
• Toxins – Poisonous
substances produced
by microorganisms
• Types
• Exotoxins
• Endotoxins
Virulence
Factors in
Bacteria
Diphtheria Toxin
Cholera Toxin
• Vibrio cholerae –
Diarrhoea
• Toxin A –
Increased cAMP –
which controls the
efflux of ions from
cells
• Increased
secretion of water
and ions into the
intestine
CFTR - cystic fibrosis transmembrane conductance regulator (CFTR)
NHE - Na+/H+ Exchanger
TCP – toxin co-regulated pili
Endotoxin
• Gram Negative Bacterial Cell
Wall – Have lipid A
(lipopolysaccharide LPS –
endotoxin).
• Important for pathogenesis.
• How are endotoxin released?
• Bacterial lysis
• Phagocytic digestion of
bacteria
• Antibiotic usage
Bacterial Toxins
Type I – Acts from outside the cell
Type II – Acts on the cell membrane
Type III – Acts inside the cell
Type I
Type II
Type III
Cholera Toxin from
vibrio cholerae
Toxic shock syndrome
toxin-1 (TSST-1) from
Staphylococcus aureus
Alpha-haemolysin from
Staphylococcus aureus
•
Bacterial Spores
Spores help bacteria survive by being resistant to extreme changes in the bacteria’s
habitat
• Temperature
• Dehydration
• Chemical insult
•
•
•
Radiation
Low nutrients
Resistant to antibiotics and disinfectants
Bacterial Spores
https://youtu.be/NAcowliknPs
Antibiotics and their role
Naturally produced antibiotics results of secondary metabolic processes
Semi-synthetic antibiotics – broader spectrum, increased efficiency
Antibiotics and their role
• Antibiotics can be toxic!!!
• Testing through animal studies –
proper dosage
• Antibiotic Resistance
• Broad Spectrum vs Narrow Spectrum
• Prescribed for “other” infections
• Spread through veterinary medicine
practices
• Incorrect practices at hospitals
Bacteria and antibiotic resistance
Source: CDC
Bacteria and antibiotic resistance
Source: CDC
Mechanisms for antibiotic resistance
Endotoxin
and Fever
Example of pathogenic bacterial diseases: Tetanus
Disease causing organism
symptoms
Reservoir
Mode of
transmission
Clostridium tetani
Severe spasms, rigidity of
muscles, lockjaw
Soil
Puncture wounds
contaminated by
bacterial spores
Source: Royal College of Surgeons of Edinburgh, Scotland
Example of pathogenic bacterial diseases:
Anthrax (Pulmonary/Gastrointestinal/Cutaneous)
Disease causing organism
symptoms
Bacillus anthracis
1)
2)
3)
Pulmonary: Pneumonia
Gastrointestinal: GI
difficulties, vomiting of
blood
Cutaneous: Skin
lesions, toxemia
Reservoir
Mode of
transmission
Soil, Animals
Ingestion,
puncture
wounds
contaminated
by bacterial
spores
Source: US army
Example of pathogenic bacterial diseases:
Plague (Bubonic/Septicemic/Pneumonic)
Disease causing organism
symptoms
Yersinia pestis
1)
2)
3)
Bubonic: Swelling of
lymph nodes, gangrene
of extremities, spread
Septicemic: Blood clots,
necrosis
Pneumonic: Severe
infection of lungs
Reservoir
Mode of
transmission
Rodents
Rat flea bites, air,
direct contact
Source: The guardian
Example of pathogenic bacterial diseases: Cholera
Disease causing organism
symptoms
Reservoir
Mode of
transmission
Vibrio cholerae
Severe diarrhea, vomiting,
dehydration, electrolyte
imbalance
Humans,
water
Contaminated food,
water
Source: CDC, Public Health images
Example of pathogenic bacterial diseases: Typhoid
Disease causing organism
symptoms
Reservoir
Mode of
transmission
Salmonella typhi
High grade fever, rashes,
intestinal perforations
Humans
Contaminated water,
bad sanitation
Source: zipheal.com
Host Pathogen Interaction
Bacterial structure
Summary &
Recap
Bacterial classification
Biofilms
Transformation
Bacterial toxins
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