Bacteriology 2/3 Flashcards
host
any organism that supports the survival and growth of microorganisms (parasites,bacteria, virus)
saprophyte
are organisms that live on dead or decaying organic matter
usually not parasites of animals but can occasionally live in/on animals and cause disease
parasite
general term that denotes an organism that lives on or within another living organism and derives sustenance
parasite does not necessarily harm the host but has the ability to given the right circumstances
commensal
organism that lives in/on the host without causing disease
most of the bacteria that normally live in the intestines on the skin and on mucous membranes
pathogen
parasitic and saprophytic bacteria which have the potential to cause disease
dont always cause disease but become pathogenic under conditions where host animals or their tissues allow invasion and disease production
live on the host as part of the normal flora
or live in only a porprotion of animals in a population
carriers
animals with specific bacterial pathogens that is present in fewer animals within a population
pathogens may be causing subclinical disease or no clinical disease at all but still shed pathogen
most animals-normal flora
cant eliminate a bacterial pathogen from the animal population
few animals=carrier animals
can eliminate a bacterial pathogen from the animal population
Skin
NF-all over
heavy bacteria in skin folds
Ear
NF-ear flap, vertical canal, horizontal canal
sterile-after tympanic membrane (Ear drum)
gram + and yeast
udder
NF-skin and streak (teat) cancal
sterile-teat cistern
gram +
eye
NF-conjunctiva and cornea
sterile-anterior and posterior chambers
respiratory tract
NF-cranial to the larynx or upper respiratory tract
sterile-lower respiratory tract
gram + and -
urinary tract
NF-distal urethra
sterile-proximal urethra and bladder
gram + and -
genital tract
NF- vagina posterior to cervix
sterile-uterus anterior to cervix
Disease
abnormal condition affecting an animal which may be caused by external factors such as microorganisms
micro-organisms can come from exogenous or endogenous sources
Endogenous
arise from bacteria that live on skin, mucous membranes as commensals
exogenous
arise from environmental bacteria
disease occurs when impaired host defences allow these bacteria to invade (opportunistic infection)
pathogen
those bacteria capable of causing disease are called pathogens
pathogenicity
capacity of a bacteria to produce disease in a host
virulence
variation in this capacity is referred
may vary between bacteria genera, species or strains and also depend on site of infection
Obligate (True) pathogens
bacteria that must cause disease in order to be transmitted from one host to another and must also infect a host in order to survive they cant survive outside the host
opportunistic pathogens
bacteria that are normal flora or saprophytes but can cause disease when something changes in the host animals that allows them to invade and cause disease
predisposing factor for infection by opportunistic
factors causing damage to tissues and factors causing impairment of the hosts defence mechanisms that are the main reason leading to opportunistic infections caused by normal flora
introduction of microorganisms to body sites where they are not normally found
disturbance of normal flora
Infectivity
capacity of the organism to become established in the tissues of the host
involves the ability to penetrate the tissues survive the host’s defences and multiply/disseminate within the host
Numbers
number of potentially pathogenic bacteria present will also affect the development of disease
in general the more bacteria present, the more likely disease will occur but virulence does influence this
Highly virulent pathogen
little host tissue compromise and or few bacteria to cause disease
weakly virulent pathogen
lot of host tissue compromise and or many bacteria to cause disease
Intermediate pathogens
intermediate response
Presence of pathogen
bacteria that are capable of causing disease
change to the host
innate host factors that predispose to infection
external or internal factor that modify host tissue/defense mechanisms
innate host factors
species
sex
age
external host stressors
extremes of temperature
nutritional deficiencies
overcrowding
transportation
change in feed
weaning
what causes tissue damage
direct trauma/other infections/allergies
circulatory disturbances
what causes changed host responses
endocrine changes
immunosuppressive organisms
Sources of Bacteria
normal flora
animals incubating disease
animals with overt disease
carrier animals
fomites
environment
Transmission of bacteria
variety of routes
inhalation
ingestion
inoculation
transplacental
via genital tract
via umbilicus
what makes a good pathogen
ability to attach and colonize
ability to gain access to the body (invade)
ability to evade the innate defense mechanisms of the host
ability to produce molecules that cause dysfunction or damage
