Control of Microbial Growth

Question 1

Bactericide

Answer 1

substance capable of killing bacteria

Question 2

Bacteriostatic

Answer 2

inhibits bacterial growth

Question 3

Name four factors that affect microbial death rate:

Answer 3

Number of microbes
Environmental influences
Time of exposure
Microbial characteristics

Question 4

Describe the ways in which microbial cell damage can occur and the distinguishing features of each mechanism:

Answer 4

Alteration of Membrane permeability - damage to lipids/proteins of p.m. by antimicrobial agents causes cellular contents to leak into medium & interferes with cell growth (lysis)

Damage to proteins & nucleic acids - denaturation - prevention of replication & normal metabolic functions

Question 5

Used to control surgical infections in operating room & also throat losenges (carbolic acid)

Answer 5

Phenols

Question 6

Contain molecule of phenol chemically altered to reduce irritating qualities. Usually in combination with soap.

Answer 6

Phenolics

Question 7

Affect cell membranes; broad spectrum; G+ effective, some G- except pseudomoants, sporicidals - but some activity against enveloped viruses.

Skin and mucus membranes. Surgical hand scrub, pre-op skin prep

Answer 7

Biguanides

Question 8

Iodine, Chlorine - impair protein synthesis & alters cell membranes…
Antiseptics - works with all kinds of bacteria, many endospores, various fungi & some viruses

Answer 8

Halogens

Question 9

Combination of iodine & organic molecule from which iodine is released slowly - less antimicrobial activity, but do not stain and less irritating. (Betadine)

Answer 9

Iodophores

Question 10

Kill bacteria & fungi but not endospores or non-enveloped viruses; protein nature denaturation.

Answer 10

Alcohols

Question 11

biocidal or antiseptic - oligodynamic action

Answer 11

Heavy metals

Question 12

Cationic detergents; most widely used as surface-active agents; fungicidal, amoebicidal, virucidal (enveloped), but not endospores or mycobacteriua.

Answer 12

Quaternary ammonium compounds

Question 13

Solution in aqueous alcohol; alcohol helps get other things into the cell

Answer 13

Tincture

Question 14

Which microorganisms are most resistant to biocides?

Answer 14

Prions, endospores, mycobacteria, protozoa, G-, fungi…

Question 15

Which microorganisms are least resistant to biocides?

Answer 15

non-enveloped viruses, G+, viruses with lipid envelopes

Question 16

Antiseptic

Answer 16

destruction of vegetative pathogens on living tissues

Question 17

Disinfectant

Answer 17

destruction of vegetative pathogens on non-living surfaces

Question 18

Sterilization

Answer 18

Destruction or removal of all forms of microbial life including endospores with possible exception of prions

Question 19

Degerming

Answer 19

removal of microbes from limited area, such as skin or around injection site

Question 20

Sepsis

Answer 20

bacterial contamination

Question 21

Asepsis

Answer 21

absence of significant contamination

Question 22

Moist Heat

Answer 22

Boiling/flowing steam or autoclaving - leads to protein denaturation

Question 23

Pasteurization

Answer 23

heat treatment for milk - denaturation

Question 24

Dry heat

Answer 24

direct flaming/incineration/hot air sterilization - sterilization - kills by oxidation

Question 25

Filtration

Answer 25

separation of bacteria from suspending liquid - physical separation

Question 26

Cold

Answer 26

Refrigeration, deep-freezing, lyophilization - decrease chemical reactions and possible changes in proteins (slows growth)

Question 27

Osmotic pressure

Answer 27

plasmolysis - hypertonic conditions

Question 28

Radiation

Answer 28

ionizing vs. nonionizing

Question 29

Name four factors that affect chemical control of microorganisms

Answer 29

Manufacturer instructions
Nature of material being disinfected
pH of medium
Contact with microbes