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Why are bacterial toxins well-known among virulence factors?
They have limited variations in their characteristics
They can be easily purified from bacterial supernatant
They are highly specific to certain types of cells
They are difficult to isolate and study
They can be easily purified from bacterial supernatant
What is the role of horizontal gene transfer (HGT) in the evolution and spread of toxin-producing bacteria?
It prevents the acquisition of toxin genes
It only occurs through lysogenic bacteriphages
It limits the variation of toxin characterisitics
It allows rapid spread of toxin genes among bacteria
It allows rapid spread of toxin genes among bacteria
Which bacterial toxin is primarily associated with Shigella bacteria but can also be produced by certain strains of E. coli?
Anthrax toxin
Cholera toxin
Leukotoxin
Shiga toxin
Shiga toxin
What is the primary component of LPS endotoxin found in Gram-negative bacteria?
O antigen
Lipoteichoic acid (LTA)
Phosphatidylglycerol (PG)
Lipid A
Lipid A
Which class of toxins possesses both cytotoxic and immunosuppressive properties?
Mycolactone toxins
Exotoxins
Superantigens
Peptide toxin
Mycolactone toxins
Which bacterium is responsible for causing Buruli ulcer?
Clostridium perfringens
Mycobacterium ulcerans
Vibrio cholerae
Pseudomonas aeruginosa
Mycobacterium ulcerans
Type I toxins primarily act on the:
Intracellular components
Nucleus of the cell
Mitochondria of the cell
Host cell surface
Host cell surface
Type III toxins have an A-B structure with two functional components, where the B component:
Enters the cell and targets intracellular components
Facilitates dissemination to remote organs
Possesses enzymatic activity to damage the cell
Binds to the host cell surface
Binds to the host cell surface
Superantigens exert their effects by binding to:
Macrophage surface receptors
Epithelial cell surface antigens
T-cell receptors (TCRs)
Interleukin-2 (IL-2) molecules
T-cell receptors (TCRs)
Which type of hemolysis causes the lysis of surrounding red blood cells, leaving a yellowish zone?
Beta-hemolysis
Gamma-hemolysis
Alpha-hemolysis
Non-hemolysis
Beta-hemolysis
Pore-forming toxins cause cell lysis by:
Escaping from the phagosome
Hydrolyzing mitochondrium phospholipids
Forming channels in the membrane
Killing host cells for nutrient acquisition
Forming channels in the membrane
Clostridium perfringens produces an alpha-toxin that causes:
Tetanus
Toxic shock syndrom
Gangrene
Pneumonia
Gangrene
A-B toxins, also known as Type III toxins, typically have two functional domains or subunits. The A domain is responsible for:
Mediating the transfer of the A domain
Translocation across the plasma membrane
Conferring toxic activity, usually enzymatic
Binding to host cell receptors
Conferring toxic activity, usually enzymatic
The B domain of A-B toxins:
Facilitates the translocation of the A domain across the membrane
Binds to glycolipids
Is an enzyme
Confers toxic activity, usually enzymatic
Facilitates the translocation of the A domain across the membrane
Proteolytic cleavage separates the A and B domains in A-B toxins, which remain connected by a:
Hydrogen bond
Covalent bond
Ionic bond
Disulfide bond
Disulfide bond
The host cell specificity of A-B toxins is determined by:
The A domain
The retrograde transport process
The pH-dependent process
The B domain
The B domain
AB-type toxins consist of:
A and B portions
A, B, and C portions
B and T portions
A and T portions
A and B portions
Which organism produces neurotoxins?
Clostridium botulinium
Yersinia enterocolitica
Bordetella pertussis
E. coli
Clostridium botulinium
AB-type toxins have two main portions: A and B. The A portion is responsible for:
Enzymatic activity, often ADP-ribosylation
Binding to sprecific receptors
Inserting into the endosome membrane
Facilitating toxin transfer inside the host cell
Enzymatic activity, often ADP-ribosylation
The T domain of AB-type toxins is:
Involved in toxin transfer inside the host cell
Found in all AB-type toxins
Not present in any AB-type toxins
Responsible for enzymatic activity
Involved in toxin transfer inside the host cell
What is the hallmark symptom of diphtheria?
Muscle weakness
Grayish pseudo membrane formation
Skin rash
Sever coughing
Grayish pseudo membrane formation
How does the diphtheria toxin enter the host cell's cytoplasm?
Fusion with the cell membrane
Activation of neuronal cells
Direct penetration of the cell membrane via pores
Endocytosis and translocation through the endosome membrane
Endocytosis and translocation through the endosome membrane
What is the function of the A subunit of the diphtheria toxin
Catalyzing ADP-ribosylation of EF-2
Binding to host cell receptors
Initiating endocytosis
Creating pores in the endosome membrane
Catalyzing ADP-ribosylation of EF-2
How is diphtheria toxin expression regulated in Corynebacterium diphtheriae?
By the presence of specific nutrients
By the chromosomal gene dtxR
By interactions with other bacteria
By temperature changes in the environment
By the chromosomal gene dtxR
What is the purpose of using Botox injections?
To reduce the depth of wrinkles
To treat urinary incontinence
To prevent severe scarring during wound healing
All of the above
All of the above
How is botulinum toxin protected from stomach acids and protease enzymes in the gastrointestinal tract?
The nontoxic components of the progenitor toxin provide protection
It is naturally resistant to stomach acids
It is encapsulated in a protective shell
It undergoes degradation in the stomach
The nontoxic components of the progenitor toxin provide protection
What is the specific effect of the botulinum neurotoxin on peripheral neurons?
Enhancement of muscle contractions
Inhibition of neurotransmitter release
Stimulation of cell growth
Blockage of protein synthesis
Inhibition of neurotransmitter release
What role do SNARE proteins play in normal neurotransmission?
They transport acetylcholine into presynaptic vesicles
They help mediate vesicle docking and fusion
They bind to ganglioside and protein receptors on peripheral neurons
They regulate calcium ion influx at the neuromuscular junction
They help mediate vesicle docking and fusion
What is the role of an antitoxin in the treatment of botulism?
Healing the damage caused by the toxin
Preventing the infection
Neutralizing the botulinum neurotoxin
Vaccination so the individual is not affected by the infection
Neutralizing the botulinum neurotoxin