MICRO Y1 S1: Strategies + Control

Question 1

chain of infection

Answer 1

• infectious agent (pathogen)
• reservoir - where it survives and multiplies e.g. people, water
• portals of exit e.g. skin, droplets
• means of transmission e.g. ingestion, direct/indirect contact, inoculation
• entry portal e.g. broken skin, respiratory tract
• susceptible hosts e.g. diabetics, immunosuppressed

Question 2

cleaning

Answer 2

• get rid of any moist organic matter which supports bacterial growth e.g. blood, soiled linen
• done through hot water, soaking etc
• must occur prior to sterilising or disinfecting

Question 3

sanitisation

Answer 3

• thorough cleaning to remove most microbes
• doesn’t imply disinfection

Question 4

sterilisation vs disinfection vs antisepsis

Answer 4

• sterilisation: physically or chemically removing ALL viable organisms (inc spores)
• disinfection: physically or chemically removing MOST viable organisms (may still be some spores)
• antisepsis: temporarily remove all microbes off skin e.g. alcohol, clorhexidine

Question 5

4 methods of sterilisation

Answer 5

• heat (moist or dry): highly efficient for heat-resistant materials
• radiation (UV, gamma ionising)
• filtration
• chemical (liquid/gas)

Question 6

moist heat sterilisation: efficiency, how does it work, temps, examples

Answer 6

• most efficient: kills everything b/c inactivates proteins and penetrates well
• 15 mins at 121˚C or 3.5 mins @ 134˚C - boiling @ 100˚C only kills some organisms (suitable for disinfection) but spores need higher temps
• e.g. autoclaving beakers and glassware

Question 7

dry heat sterilisation: effectiveness, how does it work, temps, example

Answer 7

• very effective but slower than moist heat
• inactivates cell components by oxidation
• 120 mins @ 160˚C or 60 mins @ 170˚C
• incineration (fire): destroys microbes e.g. inoculation loop

Question 8

UV radiation

Answer 8

• can’t penetrate well so good for disinfecting surfaces with long-term exposure
• e.g. instruments, surfaces, water
• damaging to human tissue + plastics

Question 9

gamma/ionising radiation: how does it work, what is it used for

Answer 9

• produces free radicals which break down DNA
• for heat sensitive materials + some foods e.g. gloves, needles, catheters, NOT tubing

Question 10

filtration

Answer 10

• uses a filter w/ diff pore sizes to physically remove microbes from heat-sensitive liquids and gases which can’t be sterilised otherwise
• e.g. used for surgical irrigation fluid, IV therapy

Question 11

chemical sterilisation + disinfection

Answer 11

• used for equip. that can’t withstand heat e.g. endoscopes w/ fibre optics and TUBING

Question 12

chemical sterilising agents: adv and disadv

Answer 12

• formaldehyde, ethylene oxide gas
• inactivate (alkylate) proteins and nucleic acids to kill a broad spectrum
• however toxic, flammable, irritant

Question 13

chemical disinfectants

Answer 13

• best: clorhexidine handwash
• chlorine: decontamination of blood spills
• iodine: skin prep for surgery
• alcohol: skin decontamination

Question 14

rules to follow with chemical disinfection

Answer 14

• must already be clean
• solution @ correct concentration
• every part of item must be immersed in solution for sufficient time

Question 15

classification of devices (EH Spaulding)

Answer 15

• critical items: enter sterile tissue or vascular system e.g. needles, scalpels (sterilisation)
• semi-critical items: contact w/ mucous membranes or broken skin e.g. endoscopes (free from all microbes except some spores - high level disinfection)
• non-critical items: contact w/ skin but not mucous membranes e.g. stethoscope, BP cuff (intermediate level disinfection)

Question 16

asepsis
medical asepsis

Answer 16

• asepsis: prevention of microbes from getting to a Pt
• medical asepsis: practices to limit no. of microbes

Question 17

surgical asepsis
aseptic technique

Answer 17

• surgical: keep all microbes away from tissues
• protective measures to prevent spread of infection e.g. gloves