33 Questions
What is the term used to refer to the establishment of a microbe on the body surface or mucosal layer?
Colonization
What are subjective effects experienced by a patient, such as pain and nausea, called?
Symptoms
What is the term for the number of microbes necessary to establish an infection?
Infectious dose
Which type of pathogen causes disease only when the body's innate or adaptive defenses are compromised or when introduced into an unusual location?
Opportunistic pathogen
How do Shigella cells evade host defenses?
By inducing epithelial cells to engulf them, causing macrophages to undergo apoptosis
How does Neisseria gonorrhoeae evade host defenses?
By hijacking the host system and binding complement regulatory proteins to avoid activation of the membrane attack complex
How do some bacteria interfere with opsonization?
Capsules interfere with opsonization by binding host's regulatory proteins to inactivate C3b
What mechanism do bacteria use to avoid destruction by phagocytes?
Preventing phagosome-lysosome fusion
How do some bacteria avoid antibodies?
By producing IgA protease
What is a strategy employed by pathogens to exit and spread within the host?
Causing direct or indirect damage to the host
How can phage-encoded genes alter the evolutionary trajectory of a species?
By integrating their DNA into the host DNA through lysogeny
What is the role of the TCP operon and cholera toxin in Vibrio cholerae infection?
They are encoded on a pathogenicity island and a phage, respectively
What is critical for the establishment of bacterial infection?
Adherence and colonization, including the role of pili with adhesins
How do Gram-negative bacteria deliver effector proteins into host cells?
Through secretion systems like the type III secretion system
What enables pathogenic E. coli strains to adhere tightly to host cells and cause fluid leakage?
Type III secretion system and effector proteins
What is a mechanism utilized by bacteria to penetrate the mucous membrane?
Secretion of mucinase enzymes
What are exotoxins susceptible to due to their composition?
Immune response
What is the mechanism of action of Cholera toxin?
Generating cyclic AMP
Which type of toxins cause paralysis by targeting the nervous system?
Clostridial toxins
What is another name for Botulinum toxin?
Botox
Which category of exotoxins includes hemolysins and phospholipases?
Membrane-damaging toxins
What do superantigens activate non-specifically?
T cells
What type of paralysis does Botulism toxin cause?
Flaccid paralysis
What was Botox initially used to treat?
Crossed eyes
Which category of exotoxins offers novel approaches for vaccines and therapies?
A-B toxins and membrane-damaging toxins
What is the most potent biological neurotoxin known?
Botulism toxin
What type of paralysis does tetanus toxin cause?
Spastic paralysis
What does ID50 represent?
The number of microbes required to cause infection in 50% of individuals or animals exposed to the microbes
What distinguishes Shigellosis from Salmonellosis in terms of bacterial ingestion?
Shigellosis results from ingestion of approximately 10–100 Shigella bacteria, whereas Salmonellosis may require ingestion of up to 10^6 Salmonella enterica bacteria, reflecting differences in survival in stomach acid
What is the course of infectious diseases?
Incubation period, illness phase, and convalescence
What characterizes chronic infections?
They develop slowly and last for months or years
What distinguishes latent infections from chronic infections?
Latent infections may recur if immunity weakens, whereas chronic infections last for months or years
What is the difference between localized and systemic infections?
Localized infections are limited to a small area, while systemic infections affect the entire body
Study Notes
Bacterial Exotoxins: Structure and Mechanism
- Exotoxins are secreted by bacteria or leak into tissue following bacterial lysis
- Exotoxins can act locally or systemically and are usually proteins, making them susceptible to immune response
- Exotoxins are categorized into neurotoxins, enterotoxins, and cytotoxins based on the tissues they affect
- A-B toxins, a type of exotoxin, consist of a toxic A subunit and a binding B subunit
- Cholera toxin is a classic A-B toxin that causes intestinal disturbance by generating cyclic AMP
- Clostridial toxins, such as botulism and tetanus toxins, are extremely potent and cause paralysis by targeting the nervous system
- Botulinum toxin, also known as Botox, has medical uses for treating muscle spasms and excessive sweating
- Membrane-damaging toxins, another category of exotoxins, include hemolysins and phospholipases that disrupt plasma membranes
- Superantigens are exotoxins that activate T cells non-specifically, leading to excessive immune response
- A-B toxins and membrane-damaging toxins offer novel approaches for vaccines and therapies
- Botulism toxin is the most potent biological neurotoxin known, causing flaccid paralysis, while tetanus toxin causes spastic paralysis
- Botox was initially used to treat crossed eyes and has since been adapted for various conditions involving muscle spasms and excessive sweating
Characteristics of Infectious Diseases and Microbial Pathogens
- ID50 represents the number of microbes required to cause infection in 50% of individuals or animals exposed to the microbes.
- Shigellosis results from ingestion of approximately 10–100 Shigella bacteria, whereas Salmonellosis may require ingestion of up to 10^6 Salmonella enterica bacteria, reflecting differences in survival in stomach acid.
- Commicable diseases with low infectious doses are easily spread.
- The course of infectious diseases involves an incubation period, illness phase, and convalescence. Some diseases may have a prodromal phase with vague symptoms.
- Infectious diseases can be acute (short-term illness), chronic (long-lasting illness), or latent (agent remains in host tissue without causing symptoms).
- Acute infections have rapid onset and short duration, with the pathogen being eliminated by the host's defenses.
- Chronic infections develop slowly and last for months or years, while latent infections may recur if immunity weakens.
- Latent infections may involve pathogens residing in host tissues without causing symptoms and are not contagious during latency.
- Localized infections are limited to a small area, while systemic infections involve dissemination throughout the body.
- There are 10 times more microbial cells in the human body than human cells, with some microbes being harmless commensals and others pathogenic.
- Horizontal gene transfer plays a significant role in the evolution of prokaryotic pathogens, with acquired genes organized into genomic or pathogenicity islands.
- New genes can be acquired through competence/transformation, conjugation, and phage-mediated transduction, allowing for the incorporation of foreign DNA into bacterial genomes.
Test your knowledge on the acquisition of new genes in bacteria through virions. Explore how viral DNA fragments can be incorporated into the bacterial genome and the mechanisms of gene acquisition. Learn about phage encoded genes and lysogeny.
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