Chapter 13 Part 2 Flashcards
What is the difference between an opportunistic and primary (true) pathogen?
True pathogens are capable of causing disease in healthy persons with normal immune function
Opportunistic pathogens cause disease when the host’s immune system is comprised
What factors weaken host defenses and increases susceptibility to infections?
Age
Genetic defects in immunity, and acquired defects in immunity (AIDS)
Surgery and organ transplants
Underlying disease: cancer, liver malfunction, diabetes
Chemotherapy/immunosuppressive drugs
Physical and mental stress
Other infections
What is microbial virulence and how is it determine?
Microbial virulence is the degree of pathogenicity an organism exhibits
Determined by:
The ability to establish in the host
The ability to cause damage to the host
What are virulence factors?
Any characteristic or structure of a microbes that contributes to infection and disease
What three things does establishment involve?
1) entering the host
2) attaching firmly to host tissues
3) surviving host defenses
How is establishment different in primary vs opportunistic pathogens?
Primary pathogens have the greatest ability to establish
Opportunistic pathogens are often those that cause disease but do not establish well in a healthy individual
What are portals of entry?
Routes of entry into the human body
What is the most common portal of entry?
Respiratory tract
What does the term infectious dose indicate about a microbe?
It is the minimum number of microbes needed to cause an infection
If a microbe has a high infectious dose, would it be more or less virulent than a microbe with a low infectious dose?
More virulent
What is the process of attaching to a host and the mechanisms used by microbes?
Adhesion is the process by which microbes gain more stable foothold on host tissues. Adhesion is dependent upon binging between specific molecules of host and pathogens
Bacteria:fimbriae, pili, capsules, slime layers
Fungi and Protozoa: various surface proteins
Viruses: spikes
Helminths: suckers, hooks, and barbs
What are phagocytes?
White Blood cells that engulf and destroy pathogens by means of enzyme and antimicrobial chemicals, and are often the first cells encountered by invading microbes.
What are antiphagocytic factors?
A type of virulence factor used by certain pathogens against pathogens
How do microbes avoid attachment by phagocytes?
Kill or inhibit the phagocyte with toxic substances
Secretion of slime layers or capsules
What are leukocidins?
Substances that are toxic to WBCs, including phagocytes, and are a primary mechanism of killing or inhibiting phagocytes
What are three ways microbes cause damage in the host?
Secretion of enzymes and toxins
Inducing excessive inflammation
Altering the host’s DNA in a manner that disrupts cell function
What are the four types of pathogenic enzymes?
Mucinase= digests protective mucous coating found on mucous membranes
Keratinase= digests keratin, a principle component of skin and hair
Collangenase= digests collagen, principle component of connective tissue
Hyaluronidase= digests hyaluronic acid, a cellular glue that cements many animal cells together.
How do microbes cause indirect damage to the host?
They can cause the immune response to cause as much damage than the pathogen itself. For example, inflammation is intended to activate key immune factors and facilitate the removal of pathogens, as well as their harmful enzymes and toxins. However, this process can actually cause harm and discomfort to the host.
What are the epigenetic changes caused by pathogens?
Damage to the cell
Loss of cell functions
What are the four patterns of infection?
Localized infection= microbe enters the body and remains confined to a specific tissue
Systemic infection= microbe spreads to several sites and tissue fluids, usually in the bloodstream
Focal infection= microbes breaks loose from a local infection and is carried into other nearby tissues
Toxemia= infection remains localized at portal of entry, but toxins produced by pathogen are carried to the target organ
What does it mean for microbes to enter into dormant state called latency?
It is when the initial symptoms and the infectious agents retreat.
What are asymptomatic infections?
Infections that manifest any signs or symptoms of disease
What is the reservoir of a pathogen?
The primary habitat in the natural world where pathogens originate
What is a vector and what are the most common types?
A vector is used to describe a living animal that transmits an infectious agent from one host to another, the most common types are mosquitoes, ticks, flies, and fleas.
What is the difference between a biological vector and a mechanical vector?
Biological vectors actively participate in the life cycle of the pathogen they transmit and are usually necessary for the pathogen to complete its life cycle
Mechanical vectors= not a necessary component of the pathogens life cycle, but may transmit the pathogen without being infected.
What are zoonotic pathogens?
Pathogens that are harbored or vectors by animals and are transmissible to humans
