Microbe Human Interactions: Infections and Epidemiology

patterns of infection

localized, systemic, focal, mixed, primary, secondary, acute, chronic

localized infection

microbe enters the body and remain in that specific tissue

boils,fungal skin infections, warts

systemic infection

infection spread to several sites/tissue fluids usually blood stream

viral- measles, rubella, chickenpox, AIDS

bacterial- anthrax, typhoid fever, syphilis

fungal- valley fever, cryptococcosis

nerve- rabies

cerebrospinal fluid- meningitis

focal infection

when infectious agent breaks loose from a local infection and is carried to other tissues

ex: tuberculosis, scarlet fever

toxemia

infection remains localized, toxins are carried through the blood to the target tissue

mixed infection

several agents established themselves simultaneously at the infection site

polymicrobial disease

wound infection, dental caries, human bite infection

primary infection

initial infection

secondary infection

occurs when primary infection is complicated by another infection cause by a diff microbe

acute infection

come on rapidly

often short lived

chronic infection

progress/persist over a long period of time

sign

objective change that can be observed and measured by someone other than the patient

more precise than symptoms

symptom

subjective evidence of disease as sensed by the patient

syndrome

disease identified/ defined by a certain complex of signs/symptoms

sign examples

fever, septicemia (bacteria mult in blood), microbes in tissue fluid, chest sounds, skin eruptions, leukocytosis (high WBC count), leukopenia (low WBC count), swollen lymph nodes, abscesses, tachycardia (inc heart rate), antibodies in serum

symptoms

chills, pain, ache, soreness, irritation, malaise, fatigue, chest tightness, itching, headache, nausea

asymptomatic, subclinical, inapparent infection

host is infected by doesn’t manifest disease, carrier

latency

dormant state of infectious agent

microbe can periodically become active/produce recurrent disease

ex: syphilis, typhoid fever, tuberculosis, malaria

sequelae

long term/permanent damage to organs/tissues

meningitis-deafness

strep throat-rheumatic heart disease

lyme disease- arthritis

polio-paralysis

course of infection

incubation period, prodromal period, acute phase, convalescent stage

incubation period

time from initial contact with infectious agent to appearance of first symptom

prodromal period

when the earliest notable symptoms of infection appear

acute phase

infectious agent mult at high level, exhibits its greatest virulence, become well established in target tissue

convalescent stage

patient responds to infection/symptoms decline

continuation period

patient experiences sequelae

reservoir

primary habitat in the natural world where pathogen originates

human/animal carrier: soil, water, plants

source

individual/obj from which an infection is acquired

living reservoirs

animals: directly transmit to humans, can transmit via vectors, can transmit through vehicles/water

humans: person who is fully recovered from hepatitis but is still shedding hepatitis A virus in feces

arthropods: fleas, mosquitoes, flies, ticks

indirect transmission

person with a cold contaminates pen which is picked up by healthy person

direct transmission

sick person sneezes on healthy person

asymptomatic carriers

infected by show no symptoms

gonorrhea, genital herpes with no lesions

incubating carriers

infected by show no symptoms

infectious mononucleosis

convalescent carriers

recuperating patients without symptoms

continue to shed viable microbes and infect others

chronic carriers

individual who shelters the infectious agent for long period after recovery die to latency of agent

tuberculosis, typhoid fever

passive carriers

medical/dental personnel who handler patient materials that are contaminated with patient secretion/ blood

biological vector

actively participates in pathogen life cycle, serve as site in which pathogen can mult/complete life cycle

ex: mosquito transmitting malaria

through biting, aerosol formation, touch

mechanical vectors

not necessary to life cycle of infectious agent

merely transport pathogen without being infected

zoonosis

infection indigenous to animals but also transmissible to humans

non living reservoirs

soil,water, air

most are saprobic/cause little harm to humans

communicable disease

occurs when an infected host can transmit the infectious agent to another host/establish infection in that host

contagious

agent is highly communicable, especially though direct contact

noncommunicable

doesn’t arise through transmission of infectious agent from host to host

horizontal transmission

disease is spread through pop from 1 infected person to another

direct/ contact transmission

kissing,sex

indirect transmission

fomites, vehicles, parenteral (injection into deeper tissue)

vector transmission

the transfer of pathogens (viruses, bacteria, parasites) from an infected host to a new, susceptible host via living organisms

vertical transmission

from parent to offspring via ovum, sperm, placenta, milk

congenital disease

born with it

vehicle

natural, non living material, air, water, soil, food

fomite

inanimate obj that harbors/transmits pathogens

not continuous source of infection

oral-fecal route

fecal carrier with inadequate personal hygiene contaminates food and unsuspecting person ingests it

droplet nuclei

dried microscopic residues created when microscopic pellets of mucus/saliva are ejected from nose/mouth

aerosols

suspension of fine dust/moisture particles in the air that contain live pathogens

nosocomial infection

infection disease acquired/developed during hospital/healthcare facility stay

iatrogenic infection

due to medical treatment

antibiotics that are used to treat bacteria infection may cause yeast infection

control of nosocomial infections

medical asepsis- lower microbial load in patients, caregivers, hospital setting

surgical asepsis- ensure all surgical procedures are conducted under sterile condition

handle contaminated materials carefully

frequent and thorough hand washing

isolated rooms and wards

koch postulate

aim to study infection/disease is determining etiologic agent

1) same pathogen must be present in every case of disease

2) pathogen must be isolated from the diseased host and grown in pure culture

3) pathogen from pure culture must cause disease when inoculated to healthy animal

4) pathogen must be isolated from inoculated animal/must show original organism

exceptions to koch

unique culture requirements: some can’t be cultured on artificial media

one pathogen can cause different disease states/different parts of body

similar symptoms caused by several pathogens

idiopathic disease- cause unknown