Microbio Chapter 10 - Host-Microbe Interactions and Pathogens

Delineation as “normal” or “healthy” often has to do with the _________ of the microbe rather than the species itself

location

_______ is the disruption of normal microbiota balance that can compromise health

Dysbiosis

Dysbiosis increases ________

the risk for infections and dieases

Childhood exposure to a variety of microorganisms in necessarey for

proper immune system development

Dysbiosis of the oral microbiome can lead to

periodontal disease

Major HAI C. diff infection is caused by ______ dysbiosis

gut

How does C. diff flourishes in the large intestine

Patient went through antibiotic treatment which disrupts the normal gut microbiota, allowing C. diff to proliferate.

______ is the ability of a microbe to infect a host and/or cause disease

Pathogenicity

_____ if the degree or extent of disease that a pathogen causes (disease severity) or the ability of the pathogen to multiple withing the host (pathogen’s infectivity)

Virulence

What influences pathogenicity and virulence?

Host-microbe interactions

Mechanisms used by pathogens and/or components they produce to: infect, invade, damage host tissues, overcome defenses, or achieve transmission to a new host are known as ____

virulence factors

For a pathogen to persist in a population, it must (3 things)

endure overtime

find a balance between breaking down defenses and living/reproducing within a host

get readily transmitted to a new host

Pathogens that kill hosts quickly usually

cause high mortality outbreaks

are geographically isolated

short lived in duration or in host/population

How is a virus successful?

Gets transmitted to a new host to continue their life cycle

Making virulence factors requires ______

an energy investment; only makes when needed

When pathogens are grown in the lab, they become

attenuated

What is an attenuated pathogen?

Lose virulence factors; still infectious but weakened; do not cause disease in an immunocompetent host

What are examples of bacterial virulence factors?

Adhesion, nutrient acquisition, invasion, immune system evasion, and toxins

_____ promote infection and disease by directing damaging host tissues or by disabling the immune system

Toxins

______ are microbes that make toxins

Toxigenic

______ are toxins in the bloodstream

Toxemia

Lipid A portion of LPS withing the gram-negative bacterial outer membrane; released upon cell lysis; inflammatory

Endotoxins

Proteins (often enzymes) produced and actively secreted by growing cells; active in low concentraions

Exotoxins

Endotoxins are released when

the cell wall breaks apart

When the immune system and/or antibiotics kill infecting gram-negative bacteria _____________ which may lead to ________

endotoxin levels circulating in the bloodstream may increase (endotoxemia)

septic shock

Why is septic shock hard to treat?

Antibodies like proteins, not lipids (endotoxins)

Exotoxins are soluble proteins produced and secreted by _____________ bacteria

both gram positive and negative

Exotoxins are named based on

the organism that makes it and the type of cell it targets

What are the three main families exotoxins are classified into

Type I: Membrane-acting extracellular toxin

Type II: Membrane damaging toxins

Type III: Intracellular toxins (AB toxin family)

Toxin binds at host plasma membrane to generate a signal that changes host cell gene expression; toxin does not enter cell

Type I: Membrane-acting extracellular toxin

Toxins disrupts host cell membranes by forming pores or breaking down membrane lipids; results in cell lysis

Type II: Membrane damaging toxins

Binding portion of toxin binds to plasma membrane, toxin enters cell and active portion enters the host cell to exert an effect

Type III: Intracellular toxins (AB toxin family)

_______ are toxic bacterial proteins with adverse host effects

Exotoxin

Exotoxins may exert effects

locally or systemically

_______ is not always required to be affected by toxin

infection (eg food poisoning, botox)

Exotoxins can be responsible to the

signs/symptoms of an infection

Exotoxins are often ______ - body produces anti-toxin antibodies

immunogenic

Exotoxins can be inactivated by ______ to become a toxoid that are used in _____

heat or chemical treatment; vaccines

Endotoxins are made of

made by

released from

Symptoms

Lipid A portion of LPS

Gram-negative bacteria

Cell wall when bacteria divide or die

Inflammatory/Fever

Are endotoxins used in vaccines? Can be neutralized in patient?

No

Toxicity level of endo vs exo toxins

Endotoxins - less toxic, but can cause septic shock and organ failure

Exotoxins - highly toxic

Exotoxins are made of

made by

released from

Symptoms

Proteins

Gram negative and positive bacteria

Actively growing bacteria or lysis

Sometime fever — specific for a particular cell

Are exotoxins used in vaccines? Can be neutralized in patient?

Yes, some can be used as vaccines and can be neutralized with specific antibodies.

What is the infectious dose-50 (ID50)

The number of pathogens needed to establish an infection in 50% of exposed hosts

More infectious pathogens have a ______ ID50

lower

What is Lethal dose-50 (LD50)?

The amount of a pathogen required to kill 50% of affected hosts that are not treated

A lower LD50 = _____ virulence

higher

What portal of entry for bacillus anthracis is more virulent?

Skin

On both an ID50 and LD50, higher virulence in left/right of lower virulent?

shifted left

What are the 5 steps to infection?

Enter the host; adhere to host tissues and colonize; obtain nutrients and invade; replicate while warding off immune defenses; transmit to a new host

What is a portal of entry?

Any site that a pathogen uses to enter the host

Portal of entry is determined by

mode of transmission

What is the most common portal of entry?

Mucous membranes

Pathogen Must Adhere
Surface molecules on pathogen termed ______ bind to specific

adhesins; receptors

Pathogen Must Adhere
______ are bacterial adhesions that assemble into hair-like appendages and extend from the cell surface

pili or fimbriae

Pathogen Must Adhere
Species and tissue tropism is due to

specificity for attachment to a particular host cell surface marker

Tropism def

Preference of a pathogen for a specific host and/or a specific tissue within the host

If adhesins and/or receptors can be altered or masked to interfere with attachment, infection (and therefore disease)

can be prevented or controlled

_____ block pathogen adhering

antibodies - bind to virus instead of virus to host cell

_______ involves biofilm formation

Colonization

_____ microbial cells embedded in matrix of extra polymeric substances (EPS)

biofilms

EPS matrix contains a wide variety of

polysaccharides, glycoproteins, glycolipids, extracellular DNA of microbial origin

_________ cell to cell chemical communication system allowing microbes encased within the biofilm to coordinate activities/alter gene expression to benefit the community

quorum sensing

Are biofilm or planktonic harder to kill?

biofilm bacteria

Once adhered, a pathogen may

remain on the surface

reside in the cell

invade deeper by passer through cells

pass between cells

_____ are membrane associated enzyme virulence factors that function to assist microbial invasion

invasins

Invasins act locally to _____ or have an immediate effect of ______

damage host cells

facilitating the growth and spread of the pathogen

Most cellular pathogens require _____ to survie

Iron

There is little iron freely circulating in host tissues/blood, so bacteria need to produce

membrane bound iron0binding proteins and secreted iron binding siderophores

As pathogens establish an infection and invade, death or damage occurs to host cells and tissues

Cytopathic effects

Cellular pathogens induce cytopathic effects are they

invade host cells, release toxins, and exploit host nutrients

Viral pathogens generate cytopathic effects when they

disrupt normal host cell function, release from the host cell, and transform normal cells into cancer cells

What is a by product of fighting infections from immune system

Damage on the body

Antigen masking

Pathogen is covered in host factors to avoid immune detection

Antigen mimicry

Pathogen’s antigens resemble host molecules, helping it evade immune detection

Antigen variation

Pathogen switched its antigens, thwarting the mounting immune response

______ pathogens reside, multiply, and survive inside the host cells

Intracellular

____ is the ability of a pathogen to remain dormant and causes persistent or recurrent disease

Latency

Pathogens can _____ the immune response and interfere with

suppress

phagocytosis

How do pathogens suppress the immune response?

Target the immune cells directly to disrupt function

Make proteases to break down immune effectors like antibodies

Interfere with signals and factors that activate specific immune responses

Pathogens can escape phagocytosis by

Releasing toxins that kill phagocytes

Producing a capsule

Blocking phagosome-lysosome fusion

Escaping phagosome

Adapting to hard environment or neutralizing hydrolytic enzymes

Reservoir is the

habitat where the pathogen is typically found

Any route a pathogen uses to exit its host is a

portal of exit

What BSL levels are in most laboratories, hospitals, and health care settings?

1 and 2

What BSL levels are restricted to approve clinical and research facilities?

3 and 4

Agents are likely to cause serious or lethal human disease for which preventative or therapeutic interventions are not available

BSL 4

Agents are associated with serious or lethal human disease for which preventative or therapeutic interventions may be available

BSL 3

Agents are associated with human disease which is rarely serious and for which preventative or therapeutic interventions are often avaible

BSL 2

Agents are not associated with disease in healthy adult humans

BSL 1

What are standard precautions?

Designed to limit transmission of pathogens and are universal standard precautions in all health care facilities

What are transmission precautions?

Used in addition to standard precautions for patients infected with certain infectious agents for which additional precautions are needed to prevent infection transmission

What are the 3 main types of transmissions?

Contact, droplet, and airborne diease

What are examples of transmission precautions?

Limit patient transport, gloves, gown, mask