4. Invasion

Question 1

what is the cause of flatulence

Answer 1

carbon dioxide produced by microbes

Question 2

what do farts produced by sulphate producing bacteria smell like, why?

Answer 2

smells of rotten eggs

producing hydrogen sulphide

Question 3

what other factors contribute to flatulence

Answer 3

consuming fizzy drinks and foods rich in fibre

Question 4

define disease

Answer 4

a pathological condition characterised by an identifiable group of signs or symptoms

Question 5

define infection

Answer 5

invasion of a hosts bodily tissues by a pathogen, which then multiplies and produce toxins

Question 6

define pathogenicity

Answer 6

the ability to cause disease

Question 7

define virulence

Answer 7

the degree/ intensity of pathogenicity

Question 8

what is the infective dose

Answer 8

the number of bacterial cells required to establish an infection

Question 9

what does a low Infective dose signify

Answer 9

a more virulent pathogen

Question 10

what carries virulence factors

Answer 10

plasmids

Question 11

what are primary pathogens

Answer 11

the microorganisms that cause diseases in healthy individuals

Question 12

what are opportunistic pathogens

Answer 12

microorganisms that are ordinarily in contact with the host, but only cause disease when the host’s resistance is low

Question 13

what three things must be present to cause a disease

Answer 13

a susceptible host
a conductive environment
pathogen

Question 14

what is a reservoir

Answer 14

where the bacterium normally resides, here it causes no harm

Question 15

name 2 non-human reservoirs

Answer 15

environment - soil, water, fomites

animals - zoonosis

Question 16

what are fomites

Answer 16

objects that carry materials, e.g. bedding, door handles

Question 17

what pathogen is commonly found on fomites

Answer 17

staphylococcus aureus (MRSA)

Question 18

what does zoonosis mean

Answer 18

the term for animal reservoir

Question 19

in plague what is the vector and what is the reservoir

Answer 19

vector = fleas
reservoir = rodents

Question 20

explain the case of Typhoid Mary

Answer 20

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

Question 21

what are the best reservoirs

Answer 21

human ones that show symptoms = transmit the pathogen via coughs and sneezes

Question 22

describe the case of the 1992 TB outbreak in Italian school

Answer 22

one single teacher (symptomatic) responsible for 80% of students and all teachers being infected

Question 23

name 3 methods of pathogen transmission

Answer 23

aerosol (coughs)
direct contact
vector- borne

Question 24

name 3 of the hosts natural barriers

Answer 24

1. enzymes in the mucus, tears and saliva
2. acid in stomach
3. competition from commensal bacteria

Question 25

where is the easiest places for microbes to attach

Answer 25

sterile surfaces: e.g. prosthetic joints, pacemaker lead

Question 26

name a sterile surface in the human body

Answer 26

the kidneys and bladder

- no competing bacteria here

Question 27

what pathogen can commonly infect pacemaker leads

Answer 27

staphylococcus aureus

Question 28

what are pathobionts

Answer 28

normal flora that become pathogenic

Question 29

it is difficult for a pathogen to colonise a pre-existing biofilm, unless:

Answer 29

• the normal flora is compromised

- the bacterium has a number of virulence factors