module 1: intro to microbiology

areas that constitute medical microbiology

bacteria, mycoplasma, rickettsia, spirochetes, chlamydia, mycobacteria, fungi, parasites, viruses

host response to infection

innate immunity, inflammation, acute phase response, antibodies, cell-mediated immunity, t cells, b cells

Semmelweis

introduced the concept of antisepsis to the medical profession. noticed high rates of infection in new mothers when medical students came directly from autopsy to delivery. ordered students to wash their hands before each delivery & decreased mortality rates

Pasteur

discovered that most infectious diseases are caused by germs ("germ theory of disease"). fought to convince surgeons that germs existed and that dirty instruments & hands spread germs + disease. discovered pasteurization process which kills germs & prevents spread of disease. led to disproving the theory of "spontaneous generation" (mice originate from cheese, maggots originate from decaying meat).

Lister

promoted the idea of sterile surgery. introduced the use of carbolic acid (phenol) to sterilize instruments & clean wounds. applied concept of antiseptic use to reduce post-operative infections

Koch's postulates

1. the organism must be found in all animals suffering from the disease but not in healthy animals

2. the organism must be isolated from a diseased animal & grown in pure culture

3. the cultured organism must cause disease when introduced into a healthy laboratory animal

4. the organism must be re-isolated from the experimentally infected animals & shown to be the same as the originally inoculated pathogen

normal flora

microbes normally present in/on specific areas of the human body: mouth, nose, sputum, intestinal (GI) tract, skin, and parts of the reproductive tract

body areas that are normally sterile

blood, tissue, spinal fluid, and other body fluids such as urine, joint fluid, lavage fluid

epidemiology

investigative surveillance performed in response to microbial outbreak to identify circumstances leading to disease prevalence & prevention. the science of characterizing transmissibility of infectious diseases & monitoring effects these diseases have on public health

pathogenesis

development of disease

sporadic

occasional case of disease in a specific location or community

endemic

regularly occurring cases of disease in a specific location or community. sometimes there's a "normal" amount of prevalence of specific disease

epidemic

number of infected people in a specific location is larger than normal

pandemic

number of infected people worldwide is large, incidence spans the globe

quarantine

keep people who might have been exposed to a contagious pathogen away from others who have not been exposed

obligate pathogen

microbes that cause disease in most people (ex: anthrax)

opportunistic pathogen

microbes that are normally not harmful to humans but can/do cause disease on occasion. microbes that find themselves in an environment conducive to infection (abundant nutrients, insufficient host response)

contamination

presence of microbes but no growth or multiplication (no increasing numbers). no host response. ex: sneezing into your arm causes microbes to be present, but no infection follows

infection

presence, growth, and multiplication of microbes. presence of host response to the increasing number of microbes

disease microbe

infection causes changes in human physiology often associated with organ dysfunction

primary infection

host reacts to microbial invasion. symptoms, innate host response, adaptive response

secondary infection

second microbe invades during the course of initial infection. usually due to lowered body resistance

localized infection

microbes remain confined to particular anatomic site. ex: infection occurs at a specific site, such as a wound abscess

systemic infection

microbes spread throughout the body (system-wide) via bloodstream or lymphatics

bacteremia

bacterial presence in the blood: bacteria enters the normally sterile bloodstream. bacteria does not multiply, but do circulate throughout the whole body. in transient state & usually harmless. self-limiting usually because of host phagocytes

septicemia

bacteria enter bloodstream, multiply, & can produce toxins. very serious & can be fatal. aka blood poisoning. is a bacterial infection & may be a toxic state (toxins produced)

pathogenicity

inherent ability of microbe to cause disease

virulence

quantitative potency of an organism to produce disease: degree to which a microbe is pathogenic (able to cause disease)

exogenous

source of microbe causing disease is outside the body of person experiencing infection. ex: infection via cut acquired while gardening

endogenous

infection caused by bacteria that is a normal resident of a body location (normal flora) if it enters a sterile area of the body (like brain or muscle). ex: E. coli from the GI tract enters the urinary tract & causes a UTI

morbidity

state of disease or being diseased

mortality

death, result of disease or other reasons

etiologic agent

causative agent of disease. microbe responsible for causing infection or disease

nosocomical

hospital-acquired. patient develops infection during a stay in the hospital

iatrogenic

doctor induced, medical device-acquired. patient develops infection caused by medical device, examination, treatment, or healthcare provider

carrier

some individuals always harbor active pathogenic microbes (MRSA of the nostrils). convalescent individuals can harbor the disease agent during recovery (disease resolution not complete). active individuals can harbor disease agent after recovery (usually short-term). passive individuals harbor disease agent continually (some have symptoms, some don't). typhoid mary is an example of this who didn't show symptoms

reportable diseases

diseases that all 50 states are required to report to the CDC

notifiable diseases

diseases that are voluntarily provided to the CDC

communicable disease

easily spread, contagious

non-communicable disease

may be infectious, but not contagious

direct methods of transmission of communicable disease

person to person. ex: aerosol droplets (like from a cough), venereal disease

indirect methods of transmission of communicable disease

inanimate objects: food, water, hands, fomites (objects like doorknobs, towels), etc. also insects (like malaria from mosquitos)

portals of microbe entry

body sites that have a direct means of microbial entry into the body. ex: bloodstream (bacteremia, septicemia), abraded skin (direct access to tissue), inhalation of aerosol (direct access to lungs)

3 general methods to control spread of infectious disease (prevent transmission)

prevent contact, prevent spread of microbes, increase host resistance (vaccination, immunization)

factors influencing whether pathogenesis will follow microbe exposure

port of microbial invasion, number of invading microbes, protective defense system of the host

host defense mechanisms

innate immunity & adaptive immunity

innate immunity

defenses against any pathogen: inflammation, initial host defense

adaptive immunity

immunity or resistance to a specific pathogen: B cells (Ab), T cells (CMI). long term response

4 cardinal signs of inflammation

redness, swelling, pain, heat, loss of function (secret 5th sign)

redness

rubor (eythema). increased blood flow due to capillary vasodilation

swelling

tumor (edema). due to increased vascular (capillary) permeability & exudate accumulation

pain

dolor. due to tissue distention & release of inflammatory mediators

heat

calor. increased blood flow due to capillary vasodilation

purposes of inflammation

to localize infection, prevent spread of pathogens, destroy & detoxify pathogens, aid in repair & healing

sequence of events in inflammation

1. tissue injury

2. vasodilation

3. increased permeability

4. emigration of leukocytes

5. chemotaxis

6. phagocytosis

phagocytosis

process in which extensions of cytoplasm surround and engulf large particles and take them into the cell

phagocytes

mediators of inflammation: neutrophils, monocytes in blood, macrophages in tissue

humoral mediators of inflammation

acute phase proteins, cytokines, chemokines, complement

active immunization

activation of immune response

passive

injection of preformed antibodies through vaccination