MBIO 1220 Microbiota (13)

What is pathogenicity?

Ability to cause disease

What is virulence?

Severity of disease (ability to cause harm)

What is etiology?

Cause of disease

What is pathogenesis?

How the disease develops

What 2 types of microbiota is yours made up of?

Normal + transient microbiota

What is your normal microbiota?

Permanent residents

What is your transient microbiota?

Not permanent residents, but may be present for days/weeks/months

Where is microbiota generally localized within your body?

Exposed areas (skin, respiratory, intestinal/urinary tracts)

What parts of your body is normally free of microbes?

Internal tissues (blood, muscle, brain)

What term describes when the microbiota produces harmful substances targeted towards invaders?

Microbial antagonism

What term describes when your microbiota uses up available nutrients to prevent pathogen growth?

Competitive exclusion

Clostridioides difficile is inhibited by the normal microbiota of the?

Large intestine

If the normal microbiota of the large intestine is eliminated, what can be the result?

C. difficile can cause infection → fatal inflammation of the colon

Some bacteria produce _________ that aid digestion

“enzymes”

E. coli in the large intestine makes what 2 vitamins?

K + B

What are opportunistic pathogens?

Microbes part of the normal microbiota that normally do not cause disease but can

In what 3 cases can opportunistic pathogens cause disease?

1. Transferred to another part of the body

2. Human host becomes immuno-compromised

3. Normal microbiota is disturbed

E. coli is a normal resident of the large intestine, but if transferred to the ________ tract, it can cause infection

“urinary”

Streptococcus pneumoniae is the normal resident of the respiratory tract, but if the host is weakened, it can cause?

Pneumonia

Symptom vs. sign

Symptoms = what a patient feels (subjective)

Signs = an objective change that can be measured by a physician

What term describes a specific group of symptoms and signs that always accompany a particular disease?

Syndrome

What characterizes a communicable disease?

Spreads from one host to another

What characterizes a contagious disease?

Spreads easily

What characterizes a non-communicable disease?

Does not spread between people (e.g. heart disease)

What are the 5 periods of infectious disease?

Incubation → prodromal → illness → decline → convalescence

What does the incubation period represent?

Time between initial infection + first signs/symptoms

What does the prodromal period represent?

Early + mild symptoms

What does the period of illness represent?

Most severe signs + symptoms, active immune response, if disease is not overcome → death

What does the period of decline represent?

Signs + symptoms subside over hours/days, patient vulnerable to secondary infections

What does the period of convalescence represent?

Recovery, but the pathogen can still be present (months/years) + spread to others

What are the 3 durations of symptoms?

Acute, chronic, latent

What is the acute duration of symptoms?

Rapidly developing + short duration

What is an example of an acute infection?

Influenza (cold)

What is the chronic duration of symptoms?

Slow developing + continual duration

What is an example of a chronic infection?

Tuberculosis

What is the latent duration of symptoms?

Inactive for a period of time + can be reactivated

What is an example of a latent infection?

Cold sores (herpes virus)

Likelihood of disease increases as?

Microbe number increases

What are the 2 types of doses that express virulence + pathogenicity of a microbe?

Infectious dose + lethal dose (potency)

How would you express an infectious dose?

ID₅₀ = “Causes infection in 50% of the population”

How would you express a lethal dose?

ID₅₀ = “Kills 50% of the population”

What is a localized infection?

Confined to small area of the body

What is a systemic infection?

Microbes/toxins spread throughout the body

What is septicemia?

Systemic infection of the blood

Under septicemia, what is bacteremia?

Bacteria in the blood

Under septicemia, what is toxemia?

Toxins in the blood

Under septicemia, what is viremia?

Viruses in the blood

What is sepsis?

Life threatening systemic inflammatory response to infection (overreaction of the immune system)

Clostridium tetani causes infection of a ___, releasing ______ into the blood

“cut,” “toxins”

Koch’s Postulates allows the determination of specific microorganisms that cause disease, with what 4 rules?

1. The same pathogen should be present in every case of the disease

2. The pathogen must be isolated + grown in pure culture

3. Pathogen from pure culture should cause disease when inoculated into a healthy lab animal

4. The same microbe should be isolated again from the inoculated individual

What are the 4 exceptions to Koch’s postulates?

1. Some bacteria will not grow in pure culture

2. Some pathogens cannot infect (lab) animals

3. Sometimes several microbes can cause 1 disease

4. Sometimes 1 pathogen can cause several diseases

Treponema pallidum is the causative agent of?

Syphilis

What is an example of a pathogen that cannot infect animals?

HIV

Streptococcus pyogenes is an example of a pathogen capable of causing several diseases, 3 of which are?

Strep throat, skin infections, scarlet fever

What are the 2 steps of a pathogen to establish infection?

Adherence → Invasiveness

What are the surface molecules that pathogens use to attach called?

Adhesins

Pathogens often stick to specific receptors on the host cell surface, 4 examples of which being?

Bacterial capsules, pili, fimbriae, viral spikes

What is “invasiveness”?

Ability of a pathogen to invade + multiply in tissues

What 2 types of molecules promote invasiveness?

Exoenzymes + invasin

What do exoenzymes do?

Degrade/alter host cells + tissues

What does fibrinolysin degrade (exoenzyme)?

Fibrin clots (S. pyogenes)

What does collagenase degrade (exoenzyme)?

Connective tissue (Vibrio + Clostridium)

What does coagulase promote (exoenzyme)?

Blood clots around bacterial cell (Staphylococci)

What are invasin + how do they promote invasiveness?

Surface proteins that cause rearrangement of the host cells cytoskeleton → forces host cell to take in bacterium

What are the 3 portals of entry for microbes?

Mucous membranes, skin, parenteral route

What are the 4 mucous membranes that are portals of entry for microbes?

Respiratory tract, GI tract, genitourinary tract, conjunctiva

The respiratory tract is the most common portal of entry, with microbes entering by?

Inhalation by nose/mouth

How do germs enter the GI tract?

Through food/water

Most microbes that enter the GI tract are destroyed by which of 2 things?

Stomach acid + bile (intestine)

What is an example of a pathogen that can withstand both stomach acid + bile?

Vibrio cholera

The genitourinary tract is a gateway for?

STIs

Most pathogens entering the genitourinary tract require what for entry?

Broken mucous membrane (e.g. a cut)

What is the conjunctiva?

Membrane covering the eye

Some microbes can cause infections of ____ ________ (Cutibacterium acnes)

“hair follicles”

What is the parenteral route of entry?

Microbes deposited directly into tissues when skin or membranes are broken (e.g. tick bite, contaminated syringe)

How does a bacteria cause indirect damage?

Inducing an immune response + inflammation

How does a bacteria cause direct damage?

Production of exoenzymes or toxins

What is a toxin?

Poisonous substance produced by a microorganism

What are exotoxins?

Heat sensitive, extremely toxic/lethal proteins that are excreted by bacteria

1 mg of the botulinum toxin can kill how many guinea pigs?

1,000,000

What are the 3 categories of exotoxins?

Neurotoxins, enterotoxins, cytotoxins

What do neurotoxins interfere with?

Nerve impulses

What 2 neurotoxins cause flaccid + rigid paralysis?

Botulinum toxin = flaccid paralysis

Tetanus toxin = rigid paralysis

What type of paralysis causes spasms, which can result in lockjaw + death by spasms of respiratory muscles?

Rigid paralysis

How do enterotoxins behave?

Modify intestinal cells so they continuously secrete water

The cholera toxin is an enterotoxin, which causes?

Severe watery diarrhea

Cytotoxins are general…

…cell killers

The diphtheria toxin is an example of a cytotoxin, which interferes with?

Protein synthesis killing cells (in respiratory tract)

What is an endotoxin?

A lipopolysaccharide (LPS) part of the outer membrane of gram-negative bacteria, causes problems when bacteria die → triggering their release

What 4 symptoms can endotoxins trigger?

Fever, inflammation, hemorrhaging, shock

Are exotoxins or endotoxins more toxic/potent?

Exotoxins

How are the symptoms of salmonellosis brought on, which is a food borne illness.

Endotoxin released from millions of dying bacteria

Endotoxins are only released when bacteria die, however exotoxins are released?

Outside the cell

What are the 7 damages caused by viral infections?

CPE, cell processes disrupted, intracellular structure destruction, inclusion bodies, syncytium formation, host cell lysis, indirect damage by immune response

What are cytopathic effects (CPE)?

Visible effects of viral infection

As an example of the disruption of cell processes that a viral infection can cause, what does the herpes virus affect?

Stops host cell division

Viral infections can form inclusion bodies, which consist of?

Viral parts (viral granule of sorts)

What is syncytium formation?

When several cells fuse to form 1 giant cell (e.g. measles)