MM Midterm 1 Part 2 (Notes from 09/14-10/7)

What are the mechanisms of colonization resistance?

1. Occupancy of attachment sites (preventing pathogens from attaching)

2. Consuming nutrients (making less food available for pathogens)

3. Altering the environment (making the environment less favorable for pathogens)

4. Producing inhibitory compounds (battling)

5. Interacting with host defenses (influencing barrier and immune function)

What disrupts normal microbiota?

Broad spectrum antibiotics

T or F: Broad spectrum antibiotics target both normal and pathogenic microbes

True

Why might treatment of one infection contribute to the development of another?

Reduced colonization resistance

__ are microorganisms that cause disease primarily when host defenses are compromised, microbiota is disrupted or the organism gains access to an abnormal body site

Opportunistic pathogens

What are potentials for opportunistic pathogens and examples of each?

1. Barrier disrupted - like a cut on the skin

2. Microbiota disrupted - like sickness after antibiotics

3. Immune system weakened - candida infection

4. Organism displaced - E. coli in urinary tract

What’s a primary pathogen?

a pathogen that can cause disease in an otherwise healthy host

What determines if a microbe will cause a disease?

The microbe itself, location and host

___ is contact with a microorganism

Exposure

T or F: Infection = exposure

False

What’s colonization?

when a microorganism establishes itself at a body site without necessarily causing damage or disease

__ is when a microo. successfully enters or establishes itself within the host

Infection

What is disease?

An infection that results in sufficient host dysfunction or damage to produce clinical manifestations

What are some barriers of the human body?

Intact skin, mucus, cilia, tears, saliva, stomach acid, urine flow and resident microbiota

What are some portals of entry for pathogens in the human body?

The respiratory tract, GI tract, genitourinary tract, skin and parenteral route (injection or infusion)

Does route of entry matter on if a pathogen can cause disease?

Yes

__ is the placed pathogens like to enter through the body

Preferred portal of entry

What are host defenses for the respiratory tract?

Coughing + cilia + mucus

What are the host defenses for the urinary tract and the GI tract?

UT = urine flow

GI T = peristalsis

How do pathogens avoid the human defense systems?

Adhesion

Types of adhesions are

1. pili/fimbriae

2. surface proteins

3. other microbial surface molecules

__ = specific molecules on the host cell surfaces used for identification of pathogens

Host receptors

__ is the preference or specificity of a pathogen for particular cells, tissues or hosts

Tropism

What helps determine tropism?

Receptors, if not present the pathogen cannot attach

What’s infectious dose?

The number of microo. required to establish infection

The higher __ the greater probability for a successful infection

exposure dose

What’s ID50?

The number of pathogen units needed to cause an infection in 50% of an exposed population

How do host factors influence whether exposure progresses to infection?

Things like age, immune status and genetics play a huge part on if a microbe can infect someone, it is a large depends situation

What are virulence factors?

the mechanisms that allow a pathogen to cause harm

__ is the ability to cause disease

Pathogenicity

__ is the relative degree or pathogenicity

Virulence

What’s included in the virulence tool kit?

1. Adhere - stay attached to the host

2. Invade - enter or spread through tissues

3. Acquire - obtain essential nutrients

4. Evade - survive host defenses

5. Damage - directly or indirectly harm the host

What’s the most important virulence factor?

Adhesion

What’s a siderophore?

a small molecule secreted by some microorganisms that binds iron with high affinity (AKA iron thief)

What do capsules aid pathogens in?

Being undetected in the host, therefore aiding in survival

What are some ways pathogens can evade the human immune system?

Capsules, antigenic variation, intracellular survival, interference with antibodies and resistance

__ is when pathogens change their surface antigens

Antigenic variation

T or F: Antigenic variation makes making antibodies less effective

True

What are the advantages if a pathogen can survive intracellularly?

1. Protection from antibodies

2. Access to nutrients

3. Avoidance of certain immune defenses (like phagocytosis)

__ = protein toxin produced by a microorganism and released or delivered to host cells

Exotoxins

Examples of endotoxins and what they cause are:

1. Botulinum toxin → paralysis

2. Cholera toxin → severe watery diarrhea

3. Diphtheria toxin → inhibits host protein synthesis (sometimes used for botox)

T or F: Toxins cannot act at a distance and bacterium have to invade every tissue

False, toxins can act at a distance

__ are recognized by the immune system and it triggers inflammation

Endotoxins

T or F: Virulence is multifactorial

True

What are the human layers of defense against pathogens?

Barriers → Innate immunity → Adaptive immunity

What are the physical ways that the skin acts as a barrier?

Highly connected epithelial cells, keratinized surface and continual shedding

What are the chemical ways skin acts as a barrier?

Its relatively dry, acidic and it has antimicrobial molecules

What’s the process of how innate immune cells recognize microbial features and cause inflammation?

PAMPs present → PRR recognize it → Cell activated → Inflammatory response

White blood cells are __ that are rapidly recruited, are highly antimicrobial and important for acute bacterial infections

neutrophils

Neutrophils are __ in number and have a __ lifespan.

large/reduced

__ aid in phagocytosis, cytokine production, antigen presentation and coordination of immune response

Macrophages

What’s the process of phagocytosis?

Recognition/attachment → engulfment → phagosome made → fusion w/ lysosome → microbial killing/degradation

What do complement proteins accomplish?

1. Opsonization = "Eat me - makes microbes easier for phagocytes to recognize.

2. Inflammation = "Come here"- promotes recruitment/activation.

3. Lysis = "Destroy it - the membrane attack complex can damage susceptible
   microbial membranes.

Are antibodies adaptive or innate?

Adaptive

Are complement proteins adaptive or innate?

Innate

What do antibodies do?

They neutralize, opsonize, and use complement activation

What occurs when antibodies neutralize a pathogen?

They block microbial attachment of toxins

__ is important for intracellular pathogens

Cell mediated immunity (innate)

T or F: Antibodies/phagocytes are important for extracellular pathogens

True

What are the characteristics of staphylococcus?

Gram positive cocci

Arranged in clusters

Facultative anaerobes

Catalase positive

Tolerant to salt/desiccation

Commonly associated with the skin and mucosal surfaces

What color stain will staph. have?

Purple

What’s the name of the test used to determine if a pathogen is a type of staphylococcus?

Catalase test

The catalase test is testing for the presence of __ by adding __.

catalase/hydrogen

What happens if the catalase test is positive?

You will see bubbles

How can staphylococcus species exist as normal colonizers and also cause disease?

Location of the bacteria determines whether it will be virulent or not. They are normally harmless until they have a new opportunity (like being in the bloodstream =disease, on the skin = harmless)

What are the different types of staph.?

1. S. aureus - potentially aggressive pathogen and colonizer

2. S. epidermis - common skin colonizer, opportunistic pathogen

3. S. saprophyticus - associated particularly with UTI’s in young women

What test helps differentiate the types of staph.?

The coagulase test

What does the coagulase test do?

Tests for the presence of the enzyme coagulase by adding blood plasma

__ makes a biofilm which makes it difficult to treat

S. epidermis

What’s the difference between the enzymes catalase and coagulase?

Catalase converts hydrogen peroxide to water and oxygen

Coagulase converts fibrinogen to fibrin

__ is coagulase (+) and the others are (-)

S. aureus

Why is S. aureus’ ability to secrete coagulase a virulence factor?

It uses fibrin as a protective shield from the immune system

Where does S. aureus usually reside on the body?

The skin and nostrils

When does S. aureus cause disease?

When barriers are disrupted like a cut or surgery or catheter insertion

Why is S. epidermis important clinically?

There is a potential issue of contamination while drawing blood or any type of implant, and its presence of biofilms makes it a persistent infection if inside the body

S. aureus is where we get __.

deep staph infections

S. saprophyticus is where we get __.

UTI’s in young women