resident flora
microorganisms that live on or within the body in non sterile areas without causing harm as long as skin and mucosa are intact
examples of sites where normal flora are found
eyes, nose and throat, skin, large intestine urinary and reproductive systems
What do resident flora do?
physically block the attachemetn of pathogens or secrete molecules that inhibit pathogen growth = can cause opportunistic infections if they enter body through wound, surgical incision, after dental work, or a catheter, or enter bosy of immunocomprimised
How do resident flora cause infection?
When misplaced ... fecal flora (e cloi normal flora of rectum) to UI or abdominal cavity or skin flora to catheter
communicable diseases
person to person, infected blood or body fluids, caused by microorganisms that live and reproduce in a human host ... all communicable diseases are infectious but not all infectious diseases are communicable
pathogens
disease producing microorganisms = cause disease by binding to specific receptors on human host cell
3 ways pathogens cause disease in human host cell
1 - direct destruction of host cell
2 - interference with the host's metabolic function
3 - exposing the host cell to toxins produced by pathogen
pathogenicity
qualities of pathogens that promote infection and disease
What factors affect pathogenicity?
virulence
inefectivity
toxigenicity
antigenicity
antigenic variability
pathogenic defense mechanisms
confection
superinfection
reservoirs
people, equipment, water, animal
BREAK CHAIIN = SANITIZING ENVIRONMENT OR ANTIMICRROBBIAL DRUGS TO CARRIER
portals of exit
excretions, secretions, skin, droplets
BREAK CHAIN = HANDWASHING, COVERING AREAS OR TRASH DISPOSAL
means of transmission
direct contact, droplet, vectors, airborne
BREAK CHAIN = ISOLATION, FOOD HANDLINGG, AIRFLOW CONTROL, UNIVERSSAL PPRECUATIONS, STERILAZATION, HAND WASHING
portal of entry
mucous membranes, gi tract, gu tract, respiratory tract, broken skin
susceptible host
immunosupression, diabetes, surgery, burns, elderly
infectious agents
bacteria, fungi, viruses, protozoa, rickettsiae
bacteria
single celled microorganism without membrane organelles, can live indepently
aerobic = need oxygen
anaerobic = no oxygen
endotoxins
contained in structural part of bacterial wall and cause inflammatory resonse in host cell
exotoxins
some bacteria produce toxins and results in host cell lysis or dysfunction .. potent proteins released in surrounding tissues = cause local or systemic injury to the host
EX. = neurotoxin = target tissue can be brain and spinal cord
enterotoxic (GI), hemo
virus
obligate intracellular parasites that need host for metabolism and reproduction
causes cells to proliferate rapidly and randomly
insert their genome into host cell
latency
chronic viral infection of dormancy = causes minimal damage but when immunocomprimised or stress triggers replication
fungi
common resident microbes that inhabit skin surface or mucous membranes ... kept in line by intact skin, inflammatory and immune cells
EX = yeast infection
yeasts
unicellular form of fungi
molds
multicellular forms of fungi
pseudohyphae
yeast that reproduce and form an elongated chain
hyphae
mold colonies that have tubules that branch
mycelium
clusters of hyphae
obligate parasites
need host to live
facultative parasites
can live independently
protozoa
somw are parasites ... transmitted through sexual contact, foood , water, or vector = deprive host cells of nutrition causing tissue destruction
EX = MALARIA, TRICHOMONAS VAGINALIS
direct contact
passsed to susceptible pperson when contacted with infected skin, mucus membranes, orr body fluid ... touching surface that iis contaminated with pathogen
droplet spread
spread in respiratory secretions of infected person = cough, sneeze, or breath
person becomes infected if droplet enters eyes, nose or mouth directly or via contaminated hands
indirect transmission
occurs when organism is spread from infected person to suusceptible person via intermediary or go between
via the air = airborne
via an insect = vector
phases of acute infection
exposure
incubation
prodrome
clinical illness
covalescense
exposure
pathogen enters host through contact
incubation
extends from exposure to onset of symptoms and signs ... doessn't know their sick
transmission to others is greatest
prodrome
onset of vague, nonspecific signs
ex = fatigue, weakness
clinical illness
full signs and symptoms of specific disease
septicemia
occurs when micrrooorganisms gain acccess to the blood and circulate throughout the body
chronic infection
infections lasting from several weeks to years ... important to tell patiennts to complete courses of antibiotics ...
local manifestations of infection
heat, pain,, edema, rednesss, lymph nodee enlargemennt and pain, purulent exudate
systemic manifestations of infection
feever, weakness, heaadacche, malaise, anorexia, nausea
treatments of infection
antibiotics, antiifungals, antivirals, symptom reduction
antibiotics
inhibit bacterial cell wall synthesis and disable protein synthesis
antivirals
limited success b/c virus employs the host thus destroying the host cell
antifungals
bind to fungal wall cell increasingg permeability
herpes
diagnosis from vesicles or ulcers or serological tests:
treatment = antivirals (orallly, IV, topicaally) can shorten course and reduce severity but not eradicate; cold compress and pain relievers
Complications = spread from mother to infant viaa lesions o
chlamydia
most common STD ... 3-4 mill new cases yr. ...
simillar to gonorrrhea
Women: cervicitis and urethritis - can cause steriltiy
Men: non gonoococcal urethritis - uretheral inflammation with frequency and burning on urination - can cause epididymitis
condylomas
anal or genital warts
influenza
patho=viral infection of the epithelial ceells of airway; transmmitteed via droplet; infected epithelial cell necrosis impairs cillia, mucous and antibodies leading to bacterial pneumonia.
clinical manifestations=cough, sore throat, nasal congestion oor d