Principles of Infection (week 2 pt.2)

the result of pathogen invasion and cellular, tissue, and organ destruction

infection

develops from the interaction btwn the pathogen and host response

disease

first line defenses

skin, mucous membranes, secretions of skin and mucous membranes

second line of defense

phagocytic leukocytes, antimicrobial proteins, inflammatory response, fever

third line defenses

lymphocytes, antibodies, memory cells

resident flora, resident microbes, microflora, microbiome, commensal organisms

microbiota

microbiota live in ___ parts of the body

nonsterile

implicated in altered immune responses and increased infection susceptibility

dysbiosis

• compete with pathogens

• immune system development, induce IgA

• stimulate intestinal epithelial cell growth/differentiation

• ferment non-digestible fibers

functions of the microbiota

organism is present but not causing symptoms

colonization

organism invades tissue and multiplies

infection

illness resulting from tissue damaged due to infection

infectious disease

any organism that produces disease

pathogens

• cause disease in healthy people

• bypass normal defenses and cause infection

• associated w/ a specific and recognizable disease

true pathogens

part of our normal flora but can cause illness if the conditions are right

opportunistic pathogens

opportunistic pathogens often cause

superinfections

communicability

ability to spread from person to person

infectivity

ability to invade and multiply in the host

immunogenicity

ability to stimulate the immune response

antigenic variability

ability to alter antigens recognized by immune cells

virulence

capacity to cause severe disease; potency

• age

• comorbidities

• genetics

• immune status

• microbiome

host susceptibility factors

3 main ways for microbes to cause symptoms

direct cell injury, toxin-mediated injury, host immune response

adaptive and innate immune responses are

host immune response

how disease-causing agents move from their reservoir to a new host

transmission

• close physical contact

• short-range respiratory droplets

direct transmission routes

• fecal oral

• vectors

• long-range aerosol

indirect transmission

infections that can spread between humans and animals

zoonotic

person who can transmit disease to others (may be asymptomatic)

carrier

vertical transmission

passed from mother to baby during pregnancy, childbirth, or breastfeeding

horizontal transmission

typical spread of infection from person-to-person

diseases w/ relatively high, but constant, rates of infection in a particular population

endemic

sudden rise of disease cases in a localized area

outbreak

sudden rise of disease cases over a larger, more generalized area

epidemic

an epidemic that spreads over a large area such as a continent or worldwide

pandemic

phases of acute infection

1. exposure

2. incubation

3. prodrome

4. clinical illness

5. convalescence

contact with pathogen

exposure

no symptoms yet

incubation

vague, nonspecific symptoms

prodrome

specific disease symptoms

clinical illness

recovery/fatigue

convalescence

two or more pathogens infect the host at the same time

co-infection

an infection that develops b/c the intial infection altered host defenses

secondary infections

new, secondary infection that is often caused by treatment-resistant microbes

superinfection

ways to identify the infectious agent

antigenic tests, antibody tests, genetic tests (PCR), direct culture

antigenic tests are ___ but some tests have high ___ ± rates

rapid, false

this type of test doesn’t indicate that you have an active infection (if positive)

antibody

PCR (genetic) tests are very ___, but must know the genetic ___ to test and you need ___ equipment

accurate, sequence, equipment

this test can be useful for determining drug sensitivity

direct culture

universal precautions mean

all blood and body fluids treated as potentially infected

infections caused by bacteria, prokaryotic microorganisms

bacterial infections

molecules or structures made by bacteria that inc. disease severity by enhancing invasion, avoiding the immune system, and causing tissue damage

bacterial virulence factors

(bacteria) adherence factors

pili, fimbriae, adhesins

(bacteria) immune evasion and defense

capsules, antigenic variation, intracellular survival, siderophores

easier for the immune system to recognize, can be easier to manage

gram + bacteria

gram positive bacteria is known for it’s thick ____ layer that causes it to turn ___

peptidoglycan, purple

often have a capsule, prone to develop antibiotic resistance, has a LPS layer (endotoxin)

gram - bacteria

enzymes released during growth

exotoxins

exotoxins damage ___ membranes, ____ second messengers, and ___ protein synthesis

cell, activates, inhibits

normal part of gram-negative cell wall

endotoxins

the LPS layer is an example of an

endotoxin

biofilms help with immune

evasion

multi-organism community that stick to surfaces

biofilms

can contain bacteria and fungi; extremely resistant to antibiotics and immune destruction

biofilms

tissue damage can be ___ or ____

direct, indirect

toxin production is a ___ tissue damage mechanism

direct

induction of the immune response via recognition of pathogen-associated molecular patterns (PAMPs) is an example of ____ tissue damage

indirect

a gram positive aerobe that around 30% of people are colonized commensally with (some strains can secrete toxins)

S. aureus

many strains of staph aureus develop antibiotic resistance and are known as

MRSA

• enzymatic destruction

• altered drug targets

• reduced permeability

• efflux pumps

• biofilm-mediated resistance

common mechanisms of antibiotic resistant organisms

basic structure is nucleic acid surrounded by a protective protein (capsid)

infectious virus

viruses cannot ___ on their own; therefore they are considered an ___ intracellular pathogen

replicate, obligate

stages of a viral infection

1. attachment

2. uncoating

3. replication

4. release

survival strategy where a virus remains dormant in a cell w/out producing more virus

viral latency

small mutations of genes that express surface molecules

antigenic drift

recombination into a new virus from 2 different species

antigenic shift

large eukaryotes w/ thick cell walls

fugal infections

most common fungal infection

Candida albicans (thrush)

fungi that can infect keratinized tissues

dermatophytes

dermatophyte infections are called ___, followed by the area infected

tinea

tinea captis

scalp

tinea pedis

foot

tinea corporis

body

tinea cruris

groin

tinea unguium

nail

parasitic infections are ___ transmitted from human to ___; and are transmitted mainly through___

rarely, human, vectors

a parasitic transmitted disease (from infected female mosquitoes), people with sickle cell trait are protected

malaria

causative agent of tocoplasmosis, parasitic protozoa most associated with risk factor in pregnancy for cat owners

toxoplasma gondii

influenza ___ is made up of single-stranded ___ and has a range of hosts including humans, birds, pigs, horse, dogs, and bats

A, RNA

influenza A is transmitted via

respiratory droplets

amoebas, flagellates, ciliates, sporozoa are all

protozoa

large, multicellular; intestinal and tissue nematodes (hookworms), liver fluke, lung fluke, tapeworm

helminths (parasitic worms)

arthropods that depend on blood from mammals; fleas, ticks, lice, mites

ectoparasites