Microbe Human Interactions: Health and Disease

colonization

microbes living in/on human body

resident microbiota

doesn’t cause disease

transient microbiota

come and go

infection

pathogenic microbe penetrate host defenses, enter tissue, mult

disease

deviation from normal health

factors for disease

infections, genetic/aging, environmental agents/chems, malfunction of systems/organs

infectious disease

disruption of tissue/organ caused by microbes/their products

pathogen

microbe capable of causing disease

pathology

study of disease

etiology

cause of disease

pathogenesis

development of disease

Human microbiome project

sequence of human biota, human cells contain 21000 proteins, 8 million microbes inhabit humans, all healthy people harbor potentially dangerous pathogens but in low numbers

benefits of normal microbiota

influence development of organs, aid digestion, make products (vitamin K- gut bacteria), prevent overgrowth of harmful microorganism

microbial antagonism

microbes in steady, established relationship are unlikely to be displaced by incoming microbes

true pathogen

capable of causing disease in healthy person with norma; immune system

opportunistic pathogen

cause disease when host defense are compromised, when they become established in part of body that is not natural to them

virulence

degree of pathogenicity

indicated by microbes ability to establish itself in host and cause damage

attenuation

weaken by growth in the labe

virulence factor

any characteristics/structure of the microbe that contributes to toxin production/induction of an injurious host response

smaller infection dose have greater virulence

ID

infectious dose

ID50= # of microorganisms required to produce a demonstrable in 50% of the test host pop

LD

lethal dose

LD50= lethal dose for 50% of the inoculated host, kills 50% of the pop

lower LD is worst, more virulent

cause of disease

entrance

attachment/adhesion

establishment/evading host defenses

causing disease/pathogenesis

exiting

parenteral route

microbes deposited directly beneath skin

punctures, injections, bites, cuts, wounds, surgery

ingestion

adapted to survive digestive enzymes/abrupt ph changes

inhalation

agent is carried to respiratory tract based on small size

sexually transmitted

urogenital tract

portals of entry examples

skin, ears, eyes, mouth, nose, mammary glands, urethra, vagina, anus

adhesion

microbes attach to host tissue

specificity

being between specific molecules on both host and pathogen

limit to types of cells it can bind to

quorum sensing

chem communication between nearby bacteria, critical to establishment of infection

adhesins/ligands

for specific proteins/glycoproteins/lipoproteins

located on pili, fimbriae, flagella,glycocalyx, capsule

virus use ___ to attach

spikes

phagocytes

white blood cells that engulf/destroy pathogen using enzymes and antimicrobial chem

antiphagocytic factors

capsules-resist phagocytosis

leukocidins- chems that kill WBCS

microbes secrete ___ and ___

enzymes, toxins

exoenzymes

secreted by pathogen

break down/inflict damage on tissue

dissolve host defense barriers/promote the spread of microbe to deeper tissue

mucinase

breaks down mucus

keratinase

breaks down keratin

toxin

specific chem product of microbe,plant,some animals that is poisonous to other organisms

exotoxin

secreted by living bacteria to host tissue

soluble to body fluids

destroy specific parts of host cell

among the most lethal substances

endotoxin

not actively secreted

ex:shed from outer membrane

how are exotoxins named

by host cell they attack

neurotoxin-act on nerve tissue

hepatotoxins- liver cells

enterotoxins-act on enteric tissue/gut

type of disease caused

diphtheria toxin

type of bacteria

botulinum toxin- clostridium botulinum

endotoxin production

part of bacterial cell wall

release to tissue when organism die

weak toxin compared to exotoxin

cause phagocytic WBC to produce cytokines

activate blood clotting

lead to necrosis of tissue, pyrogenic (fever causing)

don’t have specific method of action

produce same effect no matter the organism

portals of exit

secretion, excretion, discharge, sloughed tissue

for respiratory/salivary portals

mucus, sputum, nasal drainage, other moist secretion

skin scales

dermatophytes- athlete’s foot

virus- warts, herpes, smallpox

bacteria- syphilis, impetigo

fecal exit

diarrhea

worms release eggs/cysts through feces

urogenitial tract exit

STDs leave in host vaginal discharge/ semen

neonatal infection through birth canal

pathogens that affect kidney are discharge in the urine

removal of blood/bleeding

remove/release through vascular puncture

blood feeding insects are most common (ticks, fleas, mosquitos)