4. Invasion Flashcards
what is the cause of flatulence
carbon dioxide produced by microbes
what do farts produced by sulphate producing bacteria smell like, why?
smells of rotten eggs
producing hydrogen sulphide
what other factors contribute to flatulence
consuming fizzy drinks and foods rich in fibre
define disease
a pathological condition characterised by an identifiable group of signs or symptoms
define infection
invasion of a hosts bodily tissues by a pathogen, which then multiplies and produce toxins
define pathogenicity
the ability to cause disease
define virulence
the degree/ intensity of pathogenicity
what is the infective dose
the number of bacterial cells required to establish an infection
what does a low Infective dose signify
a more virulent pathogen
what carries virulence factors
plasmids
what are primary pathogens
the microorganisms that cause diseases in healthy individuals
what are opportunistic pathogens
microorganisms that are ordinarily in contact with the host, but only cause disease when the host’s resistance is low
what three things must be present to cause a disease
a susceptible host
a conductive environment
pathogen
what is a reservoir
where the bacterium normally resides, here it causes no harm
name 2 non-human reservoirs
environment - soil, water, fomites
animals - zoonosis
what are fomites
objects that carry materials, e.g. bedding, door handles
what pathogen is commonly found on fomites
staphylococcus aureus (MRSA)
what does zoonosis mean
the term for animal reservoir
in plague what is the vector and what is the reservoir
vector = fleas reservoir = rodents
explain the case of Typhoid Mary
human reservoir - asymptomatic carrier of salmonella typhi (can be fatal). she was a cook who had poor hygiene and so transferred the bacterium to her customers.
she was linked to 10 outbreaks of typhoid fever and 3 deaths
what are the best reservoirs
human ones that show symptoms = transmit the pathogen via coughs and sneezes
describe the case of the 1992 TB outbreak in Italian school
one single teacher (symptomatic) responsible for 80% of students and all teachers being infected
name 3 methods of pathogen transmission
aerosol (coughs)
direct contact
vector- borne
name 3 of the hosts natural barriers
- enzymes in the mucus, tears and saliva
- acid in stomach
- competition from commensal bacteria
where is the easiest places for microbes to attach
sterile surfaces: e.g. prosthetic joints, pacemaker lead
name a sterile surface in the human body
the kidneys and bladder
- no competing bacteria here
what pathogen can commonly infect pacemaker leads
staphylococcus aureus
what are pathobionts
normal flora that become pathogenic
it is difficult for a pathogen to colonise a pre-existing biofilm, unless:
- the normal flora is compromised
- the bacterium has a number of virulence factors
