Micro-organisms and the chain of infection

Question 1

what does HCAI stand for

Answer 1

healthcare associated infection

Question 2

what are the common sites of HCAIs

Answer 2

• respiratory infections
• urinary tract infections
• surgical site infections

Question 3

what are the main classifications of microorganisms that cause infection

Answer 3

• fungi
• viruses
• bacteria
• protozoa

Question 4

what is colonisation

Answer 4

Colonisation presence of bacteria on a body surface without causing disease in the person

Question 5

what are signs or symptoms of infection rather than colonisation

Answer 5

Heat, swelling, redness, pain, loss of function, pus, fever, increased heart rate, high white blood cell count

Question 6

what is infection

Answer 6

when pathogens / disease causing microorganisms gain access to host tissue and elicit an immune response

Question 7

what are commensals

Answer 7

Microbes that live in close association with their host & in the correct environment do not harm it and can positively benefit it e.g skin flora

Question 8

what are pathogens

Answer 8

Microorganisms that is able to cause disease

Question 9

what is pathogenicity

Answer 9

The ability to cause disease in a host organism

Question 10

what is pathogenesis

Answer 10

The process of how a microorganism produces disease

Question 11

what is virulence

Answer 11

The degree of pathogenicity e.g. genetic, structural or biochemical features

Question 12

what is required of a microbe to established infection in a host

Answer 12

▪ Gain access to host
▪ Adhere to, enter and move to a
favourable site within host tissues
▪ Penetrate or evade host defences in
order to multiply
▪ Dissemination of new pathogens within
or outside of the host

Question 13

what is each stage of the chain of infection

Answer 13

• infectious agents
• reservoirs
• portals of exit
• modes of transmission
• portals of entry
• susceptible host

Question 14

what are infectious agents

Answer 14

micro-organisms capable of causing disease or illness

Question 15

what are reservoirs

Answer 15

place in which infectious agents live, grow and reproduce

Question 16

what are portals of exit

Answer 16

ways in which infectious agent leaves the reservoir

Question 17

what are modes of transmission

Answer 17

ways in which the infectious agent is spread from reservoirs to susceptible hosts

Question 18

what are portals of entry

Answer 18

ways in which infectious agent enters the susceptible host

Question 19

what are susceptible host

Answer 19

individuals may have trails that affect their susceptibility and severity of disease

Question 20

what makes microorganisms good pathogens

Answer 20

• small
• flagella for movement
• multiple group together
• spores - enhance ability to survive in
  unfavourable conditions
• fimbria - enhanced adhesion to surfaces

Question 21

what are viruses

Answer 21

Much smaller than bacteria but still very effective pathogens. Structurally different depending upon the type of virus

Question 22

examples of fungi

Answer 22

• yeast e.g candida albicans
• dermatophytes - ringworm

Question 23

examples of parasites

Answer 23

• protozoa
• parasitic worms

Question 24

anti-fungal medications and where they act

Answer 24

• Cell membrane synthesis
• Form pores in cell membrane

Question 25

anti-viral medications and how they act

Answer 25

• Blocks synthesis of RNA/DNA
• Blocks cell entry/penetration
• Interferes with enzymes used to make
  RNA