Microbiology I - 20Sept2013

Question 1

Infection transmission during dental procedures is dependent on 4 factors:

Answer 1

A. Source of infection
B. Means of transmission
C. Route of transmission
D. Susceptible host

Question 2

What are the sources of infection for disease transmission?

Answer 2

1. individual suffering from acute infections “unlikely”
2. individuals in prodromal stage of infection “coming down” (stage we should be worried about)
3. Carrier (known and unknown)

Question 3

What are some means of transmission?

Answer 3

• hands
• instruments
• needles
• teeth
• saliva
• tissue appliances
• droplets and aerosols

Question 4

What are the 3 main routes of transmission?

Answer 4

1. Contact transmission: previously damaged skin or mucous membrane provides a portal of entry by touching
2. Vehicle transmission: contaminated needles, sharp instruments or flying debris (blood)
3. Airborne transmission: inhalation of contaminated aerosols

Question 5

Susceptible host acquiring an infectious disease is influenced by:

Answer 5

• route of exposure (more direct more infectious
• host susceptibility
• dose of micro-organism
• # of exposure incidents
• virulence of causative agent

Question 6

What is the equation for chance of infection in a susceptible host?

Answer 6

Infection = (virulence of organisms X number of organisms) / resistance of host

Question 7

Define universal precautions.

Answer 7

guidelines to reduce the risk of transmission of blood borne pathogens among DHCP and patients

Question 8

Define standard precautions.

Answer 8

guidelines that combined the major components of universal precautions and body substance isolates. Additional precautions are necessary for interrupting the spread of certain diseases (eg. TB) transmitted by droplets, or indirect or direct contact with contaminated sources

Question 9

What are the recommended immunizations for all staff?

Answer 9

• HBV
• influenza,
• MMR,
• polio
• tetanus
• whooping cough
• TB

Question 10

Define sterilization.

Answer 10

those processes by which all forms of microbial life are killed

Question 11

Define disinfection.

Answer 11

those processes that result in the destruction of only the vegetative forms of microbial life (pathogenic MO)

Question 12

Define antisepsis

Answer 12

the application of a chemical agent externally on a live surface (skin or mucosa) to destroy MO or inhibit their growth

Question 13

Define bactriostatic.

Answer 13

a chemical agent interferes with cell division

Question 14

Define bacteriocidal.

Answer 14

physical or chemical killing of the microorganism

Question 15

What are some low resistance microorganisms?

Answer 15

most bacteria, viruses, fungi, Streptococcus facalis, salmonella choleraesuis, pseudomonas aeruginosa, staphlococcus aureus, hydrophilc viruses

Question 16

What are some higher resistance microorganisms?

Answer 16

mycobacterium species, fungal endospores, bacterial endospores

Highest:
Creutzfeld-Jacob Disease
“Prion”

Question 17

What are the two main types of sterilizers?

Answer 17

1. Heat (main criteria for destroying microorganisms)

2. gas sterilizers: less used

Question 18

What is gravity displacement (non-vacuum) sterilizer? Type? Pros and Cons?

Answer 18

• superheated steam
• unsaturated air expelled through vent
• used to be popular, not anymore
  Type: steam sterilizer
  Pros:
• good for solid unwrapped instruments
  Cons:
• carbon steel instruments will rust
• drying cycle can take 1 further hour
• possibility of trapping expelled air
• wrapped loads (depending on packaging) can fail

Question 19

What is vacuum assisted sterilizer? Type? Pros and Cons?

Answer 19

• systems create a vacuum before chamber is pressurized (now more popular)
• allows faster and more positive steam penetration throughout the entire load
  Pros:
• good for all types of loads
  Cons:
• carbon steel instruments will rust
• drying cycle can take 1 further hour

Question 20

What is chemical vapour sterilzers? Type? Pros and Cons?

Answer 20

• use volatile chemicals (less than 12 % water)
• a combination of formaldehyde, alcohol, acetone, ketone and STEAM
  Pros:
• toxic action of chemicals and heat
  Cons:
• sterilant vapours are an irritant to staff

Question 21

What is dry heat sterilizer? Type? Pros and Cons?

Answer 21

- 160 degree cintigrade and has fan
Pros:
- used for instruments that rust
Cons:
- low temperature pockets
- cycle time 90 minutes
- damage to turbine hand pieces
- not used widely

Question 22

What are the variables contributing to ineffective sterilization monitoring?

Answer 22

• mechanical
• ineffective sterilants (chemoclaves)
• incorrect wrapping/loading of instruments
• operator error-temperature/exposure time

Question 23

What are the different kinds of sterilization monitoring tests used? What are their limitations?

Answer 23

1.Chemical indicators - not used appropriately
Limitations: does not indicate sterility
2. Biological monitors
Limitations: cannot be used for each sterilzation cycle
3. Spore strips
Procedure: put test strip inside a pack in a normal sterilzation load. Sterilze. Send to appropriate sterilzation service. - or use a self contained system.
Limitations: can’t use in every cycle

Question 24

What should you as future practitioners look for in a disinfectant?

Answer 24

• the disinfectant should kill Polio Virus and Mycobacterium

- killing times should be about 3 minutes on surfaces - 5 minutes if blood is present

Question 25

What are the desirable properties of disinfectants?

Answer 25

1. demonstrate of ability to destroy micro-organisms in low concentrations within minutes and should possess a broad spectrum anti-microbial action 2. be soluble and stable in water or other solvent vehicles without the loss of killing power 3. be relatively non-toxic for tissues 4. show good penetration power on surface when applied and should not readily combine with organic matter 5. be non-corrosive and non-staining 6. have detergent and deodorant properties-effective and pleasant

Question 26

Factors affecting germicidal activity:

Answer 26

1. concentration-determined by the manufacturer 2. time of exposure-death rate should follow a logarithmic pattern relative to time of exposure 3. Temperature- the higher the temperature the better 4. pH - anionic detergents work at acidic pH while catonic detergents work at alkaline pH 5. presence of contaminants - don't want disinfectant to combine with organic matter

Question 27

What are halogens?

Answer 27

Disinfectants a. Chlorine - sodium hypochlorite used in endodontics in irrigating root canals. forms hypochlorous acid b. iodine - direct killing of micro-organisms c. iodophors - made by combining iodine with a solubilizing agent. polyvinylpyrolidone can also be used as a surface or immersion disinfectant

Question 28

What are oxidizers?

Answer 28

``` Disinfectant hydrogen peroxide (H2O2) - reacts with SH groups of enzymes. used as mouth rinse in cases of ANUG ```

Question 29

What are heavy metal compounds?

Answer 29

Disinfectant | silver, mercury, arsenic, zinc. first used in the treatment of syphilis. silver used in dental unit waterlines

Question 30

What are alcohol?

Answer 30

Disinfectant 50-70% in water. Denatures proteins of micro-organisms. Not recommended as surface or immersion disinfectant. Ethyl alcohol or propyl alcohol.

Question 31

What are phenols (carbolic acid)?

Answer 31

Disinfectant best are the bis-phenols (chlorhexadine); can be used as mouth rinses, to treat impression material as well as dental water lines (not an skin irritant)

Question 32

What are surface tension depressors?

Answer 32

Disinfectant | soaps and detergents; not recommended

Question 33

What are chemical aerosols, peracetic acid, dyes?

Answer 33

Disinfectant | exotics (not generally used in dental offices)

Question 34

What are aldehydes?

Answer 34

Disinfectant a. formaldehyde - causes alkylation of protein of bacterial cell; isopropyl alcohol solutions of formaldehyde used for immersion disinfection b. glutaraldehyde - recommended for general disinfection of instruments and apparatus(es) Both are irritants to mucous membranes and can cause dermatological conditions

Question 35

What can disinfectants in dentistry be classified as?

Answer 35

1. immersion disinfectants 2. hard surface disinfectants 3. disinfectants used in the dental unit water supply, drains and high velocity aspirators

Question 36

Name the targeted virulence components in a bacteria.

Answer 36

flagella fimbriae (pili) capsule

Question 37

Name the targeted structural components in a bacteria

Answer 37

cell wall | cytoplasmic membrane

Question 38

Name the functions of a flagella in bacteria.

Answer 38

- locomtion- enables bacteria to follow concentration gradients, respond to physical stimuli and/or gain access to tissues

Question 39

Name the functions of fimbriae in bacteria.

Answer 39

- adherence-receptors for surface of cells - allows higher replication numbers - aggregation - allows select bacteria to aggregate and form biofilm - can be found on gram +ve and gram -ve cells

Question 40

Name the functions of capsule in bacteria.

Answer 40

- adherence - S. Mutans produces Mutan to help bind to the enamel surface - aggregation - used to help bacteria to associate - produce microenivornments - virulence - aids in avoiding phagocytosis

Question 41

Name the functions of cell wall in bacteria.

Answer 41

- filters toxic components - physical protection - adherence

Question 42

Name the functions of cell membrane in bacteria.

Answer 42

- filters toxic components

Question 43

What is sporulation? What type of bacteria is it associated with?

Answer 43

- defence mechanism against death caused by adverse environmental conditions - associated with gram +ve bacteria

Question 44

What are the 3 main sturctures in human viruses?

Answer 44

- peplomers or "spikes" - viral envelop - nucleocapsid

Question 45

What are the targets of fungi?

Answer 45

- flagella - cell wall - cell membrane

Question 46

What are the targets in protozoa

Answer 46

- cell membrane

Question 47

What are Prions?

Answer 47

"Infectious Proteins" Prions enter brain cells and there convert the normal cell protein PrPC to the prion form of the protein, called PrPSC. When normal cell proteins transform into prions, amino acids that are folded tightly into alpha helical structures relax into looser beta sheets. More and more PrPC molecules transform into PrPSC molecules, until eventually prions completely clog the infected brain cells. The cells misfire, work poorly or don't work at all.