MECHANISMS OF BACTERIAL VIRULENCE Flashcards
WHAT IS PATHOGENICITY?
THE ABILITY TO CAUSE DISEASE
WHAT IS VIRULENCE?
THE EXTENT OF PATHOGENICITY (THE EXTENT OF THE ABILITY TO CAUSE DISEASE)
WHAT ARE PATHOGENICITY AND VIRULENCE MEDIATED BY?
BY THE SO CALLED ‘VIRULENCE FACTOR’ GENES
WHAT DOES ID50 STAND FOR?
INFECTIOUS DOSE FOR 50% OF TEST POPULATION
WHAT DOES LD50 STAND FOR?
LETHAL DOSE (TYPICALLY OF A TOXIN) FOR 50% OF THE TEST POPULATION
HOW IS LD50 EXPRESSED?
the weight of chemical administered per kilogram body weight of the animal (e.g. 250ng/kg)
EXAMPLES OF VERTICAL TRANSMISSION?
- PLACENTA/BIRTH TRANSMISSION
- THROUGH GAMETES
PORTALS OF ENTRY FOR A PATHOGEN?
- MUCUS MEMBRANES (EPITHELIUM)
- SKIN DAMAGE
- VERTICAL TRANSMISSION
- SPECIALISED ENTRY (VECTOR BORNE, DELIBERATE INTRODUCTION)
DESCRIBE THE SPECIALISED PORTALS OF ENTRY FOR A PATHOGEN?
- VECTOR BORNE (INFECTION SPREAD BY ORGANISMS LIKE MOSQUITOES)
- DELIBERATE INTRODUCTION (BIOTERRORISM, NEEDLE SHARING)
WHAT ARE FIMBRIAE/PILLUS?
- PROTEIN APPENDAGES (POLYPEPTIDE CHAINS) THAT OFTEN MEDIATE INITIAL ATTACHMENT OF BACTERIA TO CERTAIN RECEPTOR STRUCTURES ALLOWING THEM TO COLONISE VARIOUS SURFACES
- THEY ARE TIPPED WITH ADHESION PROTEINS THAT BIND LIGANDS ON THE HOST TISSUE
APART FROM FIMBRIAE AND PILUS, WHAT ELSE CAN MEDIATE BACTERIAL ADHESION AND ENTRY?
FLAGELLA (HAIRLIKE STRUCTURE THAT PRIMARILY HAS A ROLE IN MOTILITY)
WHAT IS BIOFILM?
a complex structure of microbiome having different bacterial colonies or single type of cells in a group; adhere to the surface
EXAMPLES OF MEDICAL CASES WHERE BIOFILMS CAUSE PROBLEMS?
- DENTAL PLAQUES
- CYSTIC FIBROSIS (BIOFILMS FORM IN THE LUNGS, DIFFICULT TO GET RID OF, CAN BE FATAL)
- MEDICAL CATHETERS
ADVANTAGES OF A BIOFILMS FOR THE BACTERIA?
- CAN PREVENT PHAGOCYTOSIS AS A PHYSICAL BARRIER
- PREVENT ACCESS OF RECOGNITION PROTEINS
- PREVENT ACCESS OF ANTIBIOTICS AS A DIFFUSION BARRIER
- STOP CELLS BEING ‘WASHED AWAY’ AND ALLOWS DIVISION OF LABOUR
WHAT IS THE ROLE OF CAPSULAR POLYSACCHARIDES (CPS) IN BACTERIA?
- STRUCTURAL DEFENSE AGAINST IMMUNITY
- CAN PREVENT PHAGOCYTOSIS AND INACTIVATE ASPECTS OF HUMORAL IMMUNITY
WHAT ARE CAPSULAR POLYSACCHARIDES?
Polysaccharide capsules are structures found on the cell surface of a broad range of bacterial species. The polysaccharide capsule often constitutes the outermost layer of the cell, and therefore is often involved in mediating direct interactions between the bacteria and its environment. It is due to these interactions that polysaccharide capsules have been implicated as important virulence factors for many bacterial pathogens.
WHAT ARE SIDEROPHORES USED FOR BY PATHOGENS?
TO STRIP ESSENTIAL IRON FROM THE HOST CELL
WHAT IS THE MOST IMPORTANT NUTRIENT PATHOGENS NEED TO ACQUIRE?
IRON
WHAT IS NUTRITIONAL VIRULENCE?
PATHOGEN USING NUTRIENTS OTHERWISE ESSENTIAL FOR THE HOST IMMUNE RESPONSE
WHAT IS A TOXIN?
A SUBSTANCE THAT CONTRIBUTES TO PATHOGENICITY
WHAT IS TOXIGENICITY?
ABILITY TO PRODUCE A TOXIN
WHAT IS TOXEMIA?
PRESENCE OF TOXIN IN HOST’S BLOOD
WHAT IS TOXOID?
INACTIVATED TOXIN USED IN A VACCINE
WHAT IS ANTITOXIN?
ANTIBODY AGAINST A SPECIFIC TOXIN
WHAT IS BOTULINUM?
- AN EXTREMELY STRONG TOXIN
- USED IN BOTOX
- LD50: 0.03 ng/kg
LD50 FOR SHIGA TOXIN?
250 ng/kg
WHAT ARE EXOTOXINS?
TOXINS BACTERIA PRODUCE ONLY AFTER THEY ENTER A HOST I.E. TOXINS PRODUCED AND RELEASED IN RESPONSE TO HOST ‘SIGNALS’
HOW MANY GROUPS OF EXOTOXINS ARE THERE?
4
THE GROUPS OF EXOTOXINS?
- SIMPLE SINGLE POLYPEPTIDE TOXINS
- MULTI POLYPEPTIDE TOXIN COMPLEXES
- SMALL ‘DRUG-LIKE’ MOLECULES (NATURAL PRODUCTS)
- TOXINS DIRECTLY ‘INJECTED’ BY SPECIALIST SECRETION SYSTEMS
WHAT ARE SUPER-ANTIGENS?
- A TYPE OF SIMPLE SINGLE POLYPEPTIDE TOXIN
- DIRECTLY SHORT-CIRCUIT IMMUNE SIGNAL PATHWAYS; CAUSE OVERACTIVATION OF THE IMMUNE SYSTEM LEADING TO A CYTOKINE STORM
WHAT IS A CYTOKINE STORM AND WHAT ARE THE SYMPTOMS?
OVERACTIVATION OF THE IMMUNE SYSTEM (CAN BE CAUSED BY TOXINS CALLED SUPER-ANTIGENS) WHICH CAM BE FATAL
SYMPTOMS: FEVER, NAUSEA, VOMITING, DIARRHEA. SHOCK AND DEATH
SOME PATHOGENS CAN USE HOST’S IMMUNE SIGNALS AS:
GROWTH FACTORS
TOXIN GROUP ‘SMALL DRUG LIKE MOLECULES’ IS ALSO REFERRED TO AS?
NATURAL PRODUCTS
WHAT IS THE ORIGIN OF MOST ANTIBIOTICS?
MOST OF THEM ARE NATURAL PRODUCTS (SMALL DRUG LIKE MOLECULES) ISOLATED FROM BACTERIAL PATHOGENS
HOW DO BACTERIA USE ANTIBIOTICS THEY NATURALLY PRODUCE?
THEY USE THEM TO KILL OTHER BACTERIA/FUNGI
TOXINS DIRECTLY INJECTED BY SPECIALIST SECRETION SYSTEMS ARE MORE COMMON IN GRAM NEGATIVE OR GRAM POSITIVE BACTERIA?
GRAM NEGATIVE
WHAT IS A LIMITATION OF TOXINS DIRECTLY ‘INJECTED’ BY SPECIALIST SECRETION SYSTEMS?
CLOSE CONTACT WITH THE HOST CELL (E.G. MACROPHAGE) IS REQUIRED; RISK OF GETTING KILLED
HOW CAN LONG RANGE NANOSYRINGE TOXIN DELIVERY SYSTEMS BE UTILISED BY HUMANS?
HUMANS CAN PUT USEFUL SUBSTANCES IN THEM TO DELIVER VIA THE SAME MECHANISM (INSTEAD OF TOXINS, E.G. ANTIBODIES CAN BE INSERTED OR APOPTOSIS SIGNALS TO TARGET CANCER CELLS ETC.)
TOXINS DIRECTLY INJECTED BY SPECIALIST SECRETION SYSTEM RESEMBLE A:
SYRINGE
WHAT ARE THE METHODS BACTERIA USE TO DEAL WITH PHAGOCYTOSIS?
INHIBITION:
- DIRECT
- INDIRECT
- DIRECT INHIBITION BY INDUCTION OF APOPTOSIS
SURVIVING PHAGOCYTOSIS:
- INHIBITION BY INTRACELLULAR SURVIVAL IN PHAGOCYTE (LETTING ITSELF GET TAKEN UP ONCE INSIDE THE CELL ‘HIDING’ FROM THE IMMUNE SYSTEM)
