F5 Sterilization techniques and antibiotics

Question 1

aseptic / antiseptic / sterile

Answer 1

aseptic: prevent contamination with microbes (that may cause disease)
antiseptic: eliminating microbes (that may cause disease)
sterile: eliminate and prevent contamination with all microbes

Question 2

Sterilization

Answer 2

elimination of all viable cells (different from disinfection and decontamination)

• heat or heat-pressure
• radiation
• filtration
• chemical

Question 3

Decimal reduction time (D value)

Thermal death time (TDT)

Answer 3

time to achieve a 10-times reduction of cell number at a given teperature

time to achieve full sterilization at a given temperature

• depends on the organism, environmental conditions (medium, pH, nutrients)
• spores are very heat-stable

Question 4

dry sterilization

autoclave

Answer 4

oven at >170 °C for several hours

heat-pressure at 121 °C, 15-30 psi, 20 min - 2 hours

Question 5

Freezing

Answer 5

• inhibition of microbial growth
• little effect on cell viability and enzyme activity -> preservation
• some pathogens die but not all, e. g.:
- protists and multicellular parasites often die
- bacteria and fungi most often survive

Question 6

pasteurization (pastörisering)

Answer 6

complete sterilization is often neither possible nor necessary (research vs medicine vs food products)

pasteurization (pastörisering) can improve shelf life
• short heat treatment of heat-sensitive products, e.g. milk products
• no sterilization but reduction of bacterial count -> extended storage life

Question 7

filtration is used for … compounds

Answer 7

heat-sensitive

Question 8

• sterilizing agents: kill …
• disinfectants: kill …
• sanitizers: kill …
• antibiotics: kill …

Answer 8

• sterilizing agents: kill everything incl. spores
• disinfectants: kill most cells
• sanitizers: kill majority of cells
• antibiotics: kill bacteria

Question 9

• static:
• cidal:
• lytic:

Answer 9

• static: prevents growth
• cidal: kills
• lytic: kills and disintegrates (löser upp)

Question 10

Measuring antimicrobial activity, två mått:

Answer 10

Minimal inhibitory concentration (MIC)
• minimal concentration that prevents visible growth of a microorganism
• depends on organism, medium, pH, nutrients, temperature, aeration…

Minimal bactericidal concentration (MBC)
• minimal concentration that kills 99.9% of cells
• CFU determination after MIC

Question 11

Antimicrobial chemicals:

phenolic compounds

heavy metals

halogens

alcohols

surfactants

antibiotics

Answer 11

phenolic compounds
• denature proteins and disrupt membranes

heavy metals
• bind to proteins and inhibit enzymatic activity

halogens
• highly reactive, oxidize cellular components, e.g. sulfur-containing amino acids, nucleotides, fatty acids

alcohols
• denature proteins and disrupt membranes

surfactants
• lower surface tension of water, dissolve membranes (soaps, detergents)

antibiotics
• various structures and mechanisms

Question 12

Antimicrobial compounds, three types

Answer 12

• synthetic, e.g. sulfonamides
• natural, e.g. penicillin
• semi-synthetic, natural source but chemically modified -> most modern antibiotics

Question 13

anitmicrobial compounds are classified according to:

Answer 13

• structure
• mechanism of action
• activity spectrum

Question 14

anitmicrobial compounds are classified according to:

Answer 14

• structure
• mechanism of action
• activity spectrum

Question 15

antibacterial mechanisms of action, examples

Answer 15

protein synthesis (eg tetracyclines)

cell wall synthesis (eg penicillins)

Question 16

anti fungal drugs target …

Answer 16

several different cell structures

Question 17

examples of mechanistic classes

Answer 17

substrate/building block analogues
allosteric inhibitors
intercalating agents

Question 18

Antibiotic mechanisms of action: Good targets, bad targets?

Answer 18

good: cell wall synthesis
- structural targets
- multiple targets
- encoded by multiple genes

bad: nucleic acid synthesis, protein synthesis
- single protein targets
- derivatives of existing antibiotics

Question 19

antibiotic resistance mechanisms, examples

Answer 19

efflux pumps
inactivating enzymes
decreased uptake

Question 20

phenotypic resistance

intrinsic resistor

acquired resistance

Answer 20

phenotypic resistance: in some situations resistance can be achieved without any genetic alteration; this is called phenotypic resistance

• persisters (persisters are not mutants, but rather bacteria that find themselves in a favorable phenotypic niche, where they have abundances of DNA, RNA, proteins, and/or other cellular components that increase their tolerance to specific antibiotics.)
• biofilms
• swarming (Swarming motility is the rapid and coordinated multicellular migration of bacteria across a moist surface. During swarming, bacterial cells exhibit increased resistance to multiple antibiotics,)

intrinsic resistor: Intrinsic resistance is when a bacterial species is naturally resistant to a certain antibiotic or family of antibiotics, without the need for mutation or gain of further genes.

• metabolic genes
• regulators
• antibiotic inactivation
• target modification
• changes in bacterial permeability

acquired resistance

• horizontal gene transfer
• mutation

Question 21

challenges in fighting antibiotic resistance

Answer 21

• intrinsic antibiotic resistance
• acquired antibiotic resistance
• phenotypic antibiotic resistance
• horizontal gene transfer
• spread of resistant bacteria
• misuse of antibiotics
• discovery void

Question 22

solutions to breaking intrinsic antibiotic resistance:

Answer 22

• outer membrane permeabilization (combination approach)

- trapping efflux pumps

Question 23

ex of antibiotic effective against Gram- / Gram+ bacteria

Answer 23

Gram-
Polymyxins

Gram +
Penicillins

Question 24

ex of antibiotics cell wall synthesis / protein synthesis / nucleic acid synthesis

Answer 24

cell wall synthesis: Penicillins

protein synthesis: Tetracyclins

nucleic acid synthesis: Trimethoprim