Chapter 14 Microbiology Exam 3


Terms in this set (...)

commensalism symbiosis
one benefits and the other is unaffected

ex: s. epidermidis bacteria on the skin (hair mites)
mutualism symbiosis
both benefit from interaction

ex: e. coli in large intestine- they benefit from environment and we absorb nutrients they receive
parasitism symbiosis
one organism benefits at the expense of the other

host can be killed, but usually keep host alive to thrive and reproduce

ex: protozoa, fungi, bacteria, parasitic worms, mites, ticks, mosquitoes, fleas, and blood-sucking flies
any parasite that causes disease
virulence factor used by pathogens

composed of chemicals (sugars) that are normally found in body, doesn't stimulate immune response

slippery- phagocytes' pseudopods cannot grip
virulence factor used by pathogens

degrades specific molecules to enable bacteria to invade deeper tissues

digests hyaluronic acid- the "glue" that holds animal cells together
virulence factor used by pathogens

causes blood proteins to clot, providing "hiding place" for bacteria within a clot
virulence factor used by pathogens

digests blood clost, allowing subsequent invasion of damaged tissues
virulence factor used by pathogens


central to microorganism's pathogenicity in that they destroy host cells or interfere with host metabolism

neurotoxin (nerve cell function)
cytotoxin (kill host cell in general)
virulence factor used by pathogens

gm- lipid A

have outer wall membrane composed of lipopolysaccharide, phospholipids, and proteins

can be released when gm- bacteria divide, die naturally, or are digested by phagocytic cells (macrophages)

stimulates body to release chemicals that can cause fever, inflammation, diarrhea, hemorrhaging, shock, and blood coagulation

can be life-threatening from release from dead bacteria which can produce serious systemic effects in host
virulence factor used by pathogens

chemicals capable of destroying phagocytic WBCs outright
resident microbiota
here for long haul

begin to develop during birthing process

most established during first months of life

relates to commensalism- feed on excreted cellular wastes and dead cells without causing harm to person

found on skin and mucous membranes of digestive tract, upper respiratory tract, distal portion of urethra, and vagina
transient microbiota
here for short time- "hitch hiking"

eliminated by body defense cells

get out competed by resident microbes

chemical or physical changes in the body
animal reserviors
zoonoses- spread from animal hosts to humans

ex: anthrax, bubonic plague, rabies, and ebola hemorrhagic fever

acquired by direct contact, waste, eating animals, or bloodsucking arthropods
human carrier reserviors
asymptomatic- shows no symptoms but may infect others

health carriers- may have defensive systems that protect them
nonliving reserviors
ex: soil, water, and food

presence of microorganisms often due to contamination by feces or urine
portal of entry

break- abrasion, cuts, bites, scrapes, stab wounds, surgeries

can enter through natural openings- hair follicles and sweat glands

others enter by burrowing into or digesting outer layers
mucous membranes
portal of entry

line body cavities

pathogens find more hospitable and easier entry

cells are living
portal of entry

typically forms effective barrier to pathogen for fetus

if pathogens cross this portal of entry, can lead to spontaneous abortion, birth defects, or premature birth
parenteral route
entry by means in which portals of entry are circumvented

pathogens must be deposited directly into tissues beneath skin or mucous membranes

ex: punctures by nail, thorn, or needle
portals of exit
pathogens leave host

same as portal of entry- pathogens leave hosts in materials the body secretes or excretes

ex: earwax, blood, skin flakes, anus, semen and lubricating secretions, urine, milk secretions, saliva, tears, and nose secretions
role of adhesion in infection
attachment of microorganisms to cells

contain ligand- surface lipoprotein or glycoprotein molecule allowing microbe to bind to host cells

some pathogens do not attach to host cells directly, but they interact with each other to form biofilm (bacteria and polysaccharides) that adhere to surface (ex: dental plaque)
something we can see, measure, or feel

ex: rash, swelling, fever, vomiting
characteristic of disease felt only by patients

ex: pain, nausea, headache, chills, sore throat, fatigue, itching
symptoms and signs that characterize a disease or abnormal condition

ex: AIDS characterized by malaise, loss of WBCs, diarrhea, weight loss, pneumonia, toxoplasmosis, and TB
or subclinical
infections lack symptoms but may still have signs of infection

ex: leukocytosis- excess of WBCs, detected by blood sample from a person who shows no symptoms
incubation period
no signs or symptoms

time between infection and occurrence of first symptoms or signs of disease

length depends on virulence of infective agent, infective dose, state and health of patient's immune system, nature of pathogen and its reproduction time, and site of infection
prodromal period
vague, general symptoms

short time of generalized, mild symptoms that precedes illness

not all infectious diseases have this stage
illness stage
most severe or evident signs and symptoms

patient's immune system has not fully responded to pathogens and their presence is harming body

usually when physician first sees patients
decline stage
decrease of signs and symptoms

body gradually returns to normal as patient's immune response and/or medical treatment vanquish pathogens

immune response and its products (antibodies in blood) peak

if disease doesn't decline, disease can be fatal
convalescence stage
no signs or symptoms

patient recovers from illness, tissues are repaired

length of period depends on amount of damage, nature of pathogen, site of infection, and health of patient (ex: food poisoning vs. lyme disease)

disease can still be spreading during this stage
contact transmission
direct, indirect, or droplet contact
direct contact
physical touch, person-to-person

ex: touching, kissing, sexual intercourse, zoonoses, placenta, portal of exit to portal of entry
indirect contact
doorknob, laptop, pens, pencils, chairs, money that is handled

pathogens are spread from one host to another by fomites
inanimate objects that are used to transfer pathogens to new hosts

ex: needles, toothbrushes, paper tissues, toys, money, diapers, drinking glasses, bedsheets, medical equipment
droplet contact
droplets of mucus

pathogens transmitted within droplet nuclei traveling less than a meter from body during exhaling, coughing, and sneezing (ex: cold and flue viruses)

pathogens also transmitted in airborne transmission if travels more than 1 meter
vehicle transmission
spread of pathogens via air, water, food, and bodily fluids handled outside of body
airborne transmission
type of vehicle transmission

spreading of pathogens farther than 1 meter to respiratory mucous membranes of new host via an aerosol
part of airborne transmission

cloud of small droplets and solid particles suspended in air

may contain pathogens either on dust or inside droplets

can come from sneezing, coughing, air-conditioning, sweeping, mopping, changing clothes or bed linens, or from flaming inoculating loops in lab
foodborne transmission
part of vehicle transmission

inadequately processed, cooked, or refrigerated foods

contaminated with feces
waterborne transmission
part of vehicle transmission

gastrointestinal diseases- can act as reservoir as well as a vehicle of infection

fecal-oral infection- pathogens shed in feces, contaminate water source, and enter through GI mucous membrane or skin to cause disease elsewhere in body
bodily fluid transmission
part of vehicle transmission

blood, urine, saliva

ex: AIDS, hepatitis, and herpes from direct contact
vector transmission
transmission of disease by arthropods

can be either mechanical or biological
mechanical vector
type of vector transmission

present somewhere on body of insect (wing, legs)

ex: houseflies and cockroaches contaminate water and food or on skin
biological vectors
type of vector transmission

stage of pathogen's life cycle that occurs in hose

transmit pathogen and serves as host for pathogen multiplication

ex: biting arthropods- mosquitoes, ticks, lice, fleas, bloodsucking flies, bloodsucking bugs, and mites

pathogen enter new host through bite
chronic infection
disease with usually mild symptoms that develop slowly and lasts long time
acute infection
disease in which symptoms develop rapidly and runs its course quickly
subacute infection
disease with time course and symptoms between acute and chronic
communicable disease
disease transmitted from one host to another
non-communicable disease
disease not passed from person to person
primary infection
intitial infection within a given patient
secondary infection
infections that follow primary infection often by opportunistic pathogens
endemic disease
disease that normally occurs continually (at moderately regular intervals) at a relatively stable incidence within a give population or geographical area
sporadic disease
only a few scattered cases of disease occur within an area or population

occurs irregularly and infrequently
epidemic disease
when disease occurs at greater frequency that is usual for an area or population
pandemic disease
if an epidemic occurs simultaneously on more than one continent
descriptive epidemiology
careful tabulation of data concerning a disease

record location and time of cases of disease

collect patient information

try to identify index case (first case) of the disease
analytical epidemiology
seeks to determine probable cause, mode of transmission, and methods of prevention

useful in situations when Koch's postulates cannot be applied

often retrospective- investigation occurs after outbreak has occurred
experimental epidemiology
tests a hypothesis concerning cause of a disease

application of Koch's postulates

also involves studies to test a hypothesis resulting from an analytical study
healthcare-associated infections (HAIs)
infections acquired by patients or health care workers while they are in health care facilities, including hospitals, dental offices, nursing homes, and doctors' waiting rooms

most often occur in urinary, respiratory, cardiovascular, and integumentary systems, through surgical wounds than can be infected
exogenous HAI
pathogen acquired from health care environment
endogenous HAI
pathogen arises from normal microbiota within patient
iatrogenic HAI
"doctor-induced" infection

results from moderm medical procedures (catheters, invasive diagnostic procedures, and surgery)
superinfections HAI
use of antimicrobial drugs inhibits some resident microbiota allowing other microbes to thrive
role of public health agencies
enforce cleanliness of water and food supplies

work to reduce disease vectors and reservoirs

establish and enforce immunization schedules

locate and treat individuals exposed to contagious pathogens

establish isolation and quarantine measures
opportunistic pathogen
normal microbiota that become harmful if an opportunity to do so arises

conditions that create opportunities for pathogens...

introduction of member of number of microbiota into unusual site in body,
immune suppression,
changes in normal microbiota,
stressful conditions
when organism evades body's external defenses, multiplies, and becomes established in body
results if the invading pathogens alter normal body functions

also known as "morbidity"
degree of pathogenicity or relative ability of a pathogen to infect a host and cause disease
virulence factors
variety of traits that interact with a host and enable the pathogen to enter a host, adhere to host cells, gain access to nutrients, and escape detection or removal by immune system
ability of a microbe to cause disease
study of the cause of a disease
study of where and when diseases occur and how they are transmitted within populations
local infection
infection confined to a small region of the body
focal infection
infection site that serves as a source of pathogens for infections at other sites in the body
systemic infection
widespread infection in many systems of the body

often travels in blood of lymph
epidermis of skin
outer layer of skin containing multiple layers of tightly packed cells that acts as a barrier to most bacteria, fungi, and viruses

provides significant defense against colonization and infection by pathogens

their deep cells divide and push daughter cells toward surface that flatten and die, shedding dead skin cells that removes microorganisms

dendritic cells in this layer phagocytize pathogens and play a role in adaptive immunity
dermis of skin
deeper layer of the skin

tough collage fibers help skin resist abrasion that could introduce microorganisms

contains hair follicles, glands, and nerve endings

blood vessels in this layer deliver defensive cells and chemicals
secreted by sweat glands

secreted antimicrobial peptides that act against microorganisms

broad-spectrum antimicrobials that are active against many gram- and gram+ bacteria and fungi

intensive to low pH and salt

exact mechanism is unknown
secreted by sweat glands

enzyme that destroys cell wall of bacteria by cleaving the bonds between sugar subunits of the walls

bacteria without cell walls are more susceptible to osmotic shock and digestion by other enzymes within phagocytes
secreted by sebaceous (oil) glands

helps keep skin pliable and less likely to break or tear

contains fatty acids that lowers skin pH to a level that is inhibitory to many bacteria
epithelium layer of mucous membrane
thin, outer covering of mucous membranes

cells are living- diffuses nutrients and oxygen, eliminates waste

tightly packed

less efficient barrier- common portals of entry