BIO 245 Exam 3

what is drug resistance

microbes tolerate exposure to antimicrobial drugs which they were previously susceptible too

what is natural drug resistance

The ability of certain microorganisms to inherently resist the effects of specific antimicrobial drugs without prior exposure or genetic mutation.

• antibiotic procedures

• natural barriers (like the G- cell membrane)

This type of drug resistance is not a problem

how does drug resistance happen

1.) spontaneous mutations in chromosomal genes

2.) acquisition of new genes from other species

• resistance factors

• plasmids

what are the mechanisms of drug resistance

1.) Drug inactivation

2.) Permeability

3.) Uptake

3.) Change in binding site

5.) Metabolism

Drug inactivation mechanisms

• development of alternative enzymes that inactive a drug

  • requires new genes

decreased Permeability mechanisms

uptake of the drug is decreased or stopped

uptake (activation of drug pumps) mechanisms

microbe activates transport pumps to move the drug out of the cell

Change in drug binding site mechanisms

• binding sites for the drug are reduced

  • can be due to mutation or acquisition of new genes

Use of alternate metabolic pathway mechanisms

the target metabolic pathway is shut down or an alternative is used

• due to a mutation

drug example of drug inactivation mechanisms

different types of penicillin

drug example of permeability/uptake mechanisms

tetracycline and aminoglycosides ??

drug example of change in binding site mechanism

erythromycin

drug example of metabolism

sulfonamine and trimethroprim

what disease are considered the most urgent threats in terms of drug resistance by the CDC

• Clostridium difficile

• carbapenmen-resistant enterobacteriaceae

• drug resistant neisseria gonorrhoeae

clostridium difficile

• causes diarrhea and colon inflammation

• life-threatening

  • largerly problematic for hospitalized patients recently treated with antibiotics

• 500,000 infections per year

  • 15,000 deaths per year

Carbapenem-resistant Enterobacteriaceae

• nightmare bacteria

• members of the family enterobacteriaceae are resistant to almost all antibiotics

  • Klebsiella and E. coli

• generally not a risk for healthy people

  • long-term facilities, etc.

  • 9,000 infections per year

  • 600 deaths per year

What are the major factors that contribute to the problem of drug resistance

• greater use of antibiotics exerts selective pressure on susceptible bacteria and can favor survival of resistant strands

  • reduction in use could result in resistant bacteria being replaced with susceptible bacteria because resistant bacteria may be less fit than susceptible bacteria

• inappropriate prescribing

• patient non-compliance

• use of antibiotics in agriculture

what are the 3 main host/drug interaction side effects

1.) damage to tissue through toxicity

2.) allergic reactions

3.) disruption of normal microbial flora

how do we remove microbes from a given environment

• physical methods

  • heat

  • radiation

• chemical methods

  • antiseptics

  • disinfectants

what are the two main ways we control microbial growth

• physical controls

  • heat

  • radiation

  • filtration

• chemical controls

• Most work by: Disrupting cell membranes OR Altering protein and/or nucleic acid structure

Prion

• infectious protein molecule

• not considered alive

• abnormal version of a normal protein

whats the easiest to decontaminate

• bacterial vegetative cells

• enveloped viruses

• yeast

• fungal spores and hyphae

• protozoan trophozoites

whats moderately difficult to decontaminate

• protozoan cysts

• fungal sexual spores

• naked viruses

• unique vegetative bacteria

  • mycobacterium

  • gram negative pathogens

  • staphylococcus spp.

whats the most difficult to decontaminate

• prions

• bacterial endospores

sterilization

process that destroys or removes all viable microbes

• generally only non-living

• usually performed with heat

“-cide”

to kill

bactericide

a chemical agent that destroys bacteria

• excludes endospores

fungicide

a chemical agent that destroys fungi

virucide

a chemical agent that destroys viruses

sporicide

a chemical agent that destroys bacterial endospores

bacteriostatic

prevent the growth of bacteria on surfaces

microbiostasis

the inhibition of microbial growth

stasis

to stand still

Germicide

any chemical agent that kills pathogenic microbes

• can be used on living or non-living tissue

• not effective against resistant organisms

disinfection

physical process or chemical agent that destroys vegetative pathogens

• not effective against spores

• not used on living tissue

• also gets rid of toxins produced by pathogens

antiseptic chemical agents

agents that can be applied directly to living tissues to destroy vegetative pathogens

sepsis

infection of the blood

microbial load

microbial population size

sanitization

cleansing technique that removes debris, microbes, toxins, etc.

• reduces possible spoiling or infection

• soaps and detergents

degermation

reducing the load on living tissues

• alcohol swabs

the death curve

• a logarithmic curve: each increment is a 10x reduction in population size

• not every cell dies right away

• younger, more metabolically active cells die first

• sterilization is the point at which survival is unlikely

factors that effects the slope of the death curve

• the size of microbial load

• mode of action of the agent

• spores vs. vegetative cells

• other possible effects

  • mixed vs. homogenous population

  • temperature and pH of the environment

  • concentration of the agent

  • presences of inhibitors, solvents, etc.

the microbial load size effect on the death curve

the more microbes initially, the longer it takes to kill all of the microbes

mode of action of the agent effect on the death curve

if an agent is bacteriostatic it inhibits growth without killing; if bactericidal, it kills bacteria, affecting the rate at which the death curve declines.

spore vs. vegetative cells effects on the death curve

Spores are more resistant to agents than vegetative cells, leading to a slower decline in the death curve.

Modes of Action

refers to the mechanisms through which antimicrobial agents inhibit growth or kill microbes, significantly influencing their effectiveness against different microbial populations.

how does targeting the cell wall mode of action work

• prevents cell wall synthesis

• digests the cell wall

• breaks down the cell wall surface

how does targeting the cell membrane mode of action work

lowers surface tension of the membranes

how does targeting protein and nucleic acid synthesis mode of action work

• bind to ribosomes and block translation

• bind to DNA and block transcription

how does targeting protein function mode of action work

• denatures proteins

  • breaks bonds in secondary and tertiary protein structure

what happens to the cell during the cell wall mode of action

cells become fragile and lyse

what happens to the cell during the cell membrane mode of action

• cells loose ability to stop harmful molecules from moving in/out

• cells lose ability to bring essential molecules in

what happens to the cell during protein and nucleic acid synthesis mode of action

• cells can’t make proteins necessary for metabolism'

• DNA can’t be replicated

• genes can’t be expressed

what happens to the cell during the protein function mode of action

stops metabolism

examples of the cell wall mode of action

• penicillin

• detergents

• alcohol

examples of the cell membrane mode of action

• surfactants

• alcohols

examples of the protein and nucleic acid synthesis mode of action

• some antibiotics

• radiation

examples of the protein function mode of action

• heat

• organic solvents

• metals

different types of heat control

• moist heat

  • steam under pressure

  • non pressurized steam

  • boiling water

  • Pasteurization

• dry heat

  • incineration

  • dry oven

moist heat physical control

• hot water, boiling water, or steam

• 60-135 degrees Celsius

• denatures proteins and nucleic acis

dry heat physical control

• ovens

• 160-1000 degrees celsius

• denatures, oxidizes

steam under pressure

• at sea level (15 psi), water boils at 100 degrees celsius

• autoclave

nonpressurized steam

• tyndallization

• items are placed in chamber with steam from boiling water for 24 hours

• repeated 3x

• does not destroy endospores

• we use this technique because come items are too sensitive to withstand heat from autoclaving

boiling water

• boil at 100 degrees celsius

• will not destroy endospores

• easily recontaminated when removed from the water

pasteurization

• application of heat to consumable liquids to kill infectious microbes

  • maintain integrity of beverage

• Flash method

• ultrahigh temperature pasteurization

flash method of pasteurization

• exposed beverages to 71.5 degrees celsius for 15 seconds

• doesn’t kill everything

  • 20,000 cells/mL in milk is allowed

• effective against some pathogens

Ultrahigh Temperature (UHT) pasteurization method

• exposes milk to 134 degrees celsius for 2-5 seconds

• completely sterilizes milk

incineration

• bunsen burner - 1,870 degrees celsius

• incinerator - 6,500 degrees celsius

dry over

150-180 degrees celsius

how do most chemical controls work

• disrupting cell membrane or

• altering protein and/or nucleic acid structure

what is the effectiveness of chemical control determined by

• concentration

• contact time

major groups of chemical controls

• halogens

• phenol and its derivatives

• alcohols

• hydrogen peroxide

• aldehydes

• gasses

• detergents

• heavy metals

halogens

• microcidal

• sporocidal with extend exposure time

• examples:

  • flourine bromine, chlorine, iodine

limitations of halogens as a chemical control

exposure to light, alkaline pH, or organic matter can render halogens less effective

phenols

• affect protein function and/or disrupt membranes

• NOT sporidical

Alcohols

• colorless hydrocarbons with -OH groups

• ethyl and isopropyl alcohol are the only two used for microbial control

• concentration >50% destroys cell membranes

• concentration 50% - 95% denature proteins through coagulation

  • must be diluted at least 5% with water to denature proteins

• NOT sporicidal

• not very effective against viruses without an envelope

Hydrogen Peroxide

• H2O2

• forms free radicals (superoxides, hydroxyls), which are all toxic to cells

• catalase breaks down H2O2 → H2O +O2

  • won't work against elevated concentrations used during disinfection

• sporicidal at high concentrations

Aldehydes

• organic substances with a -CHO on the terminal carbon

• examples: gluaraldehyde and ortho-phthaldehyde (more potent)

• causes cross linking of proteins on the cell surface to disrupt protein activity

• sporicidal after 3 hours of exposure

• becomes unstable in increased pH and temperature

Gases

• Chlorine dioxide: disrupts proteins

  • used to treat drinking water, wastewater, medical waste, and buildings (large scale)

• Ethylene oxide gas

  • reacts with DNA and proteins

  • very effective

  • explosive

  • carcinogen

detergents

• solubilize membranes and disrupt proteins

• Cationic detergents

  • positively charged

  • more effective

    • against G+, viruses, fungi, and algae

• Nonionic detergents

  • soaps

  • not very microbicidal

    • Pseudomonas grows IN soap dishes

  • cleansing agents

Heavy Metals

• mercury, silver, gold, copper, arsenic, and zinc have all been used for centuries

  • only mercury and silver now used

• Oligodynamic

• extremly toxic, easy to develop resistance, cause allergic reactions

• bind to and inactivate proteins

oligodynamic

antimicrobial effects in very small amounts

thermal death time

the shortest exposure time necessary to kill all test microbes at a given temperature

thermal death point

the lowest temperature that can be used to kill all microbes in a sample in 10 minutes

radiation

energy emitted from atomic activity and dispersed at high velocity through matter or space

irradiation

bombardment with radiation

ionizing radiation

radiation that ejects orbital electrons from an atom

• causes ions to form

• harmful to DNA

• gamma rays and X- rays

non-ionizing radiation

radiation that excites atoms, but does not ionize them

• UV

• mutates DNA

how does ionizing radiation work

• cold sterilization: performed at low temperatures

• penetrates solids and liquids

• damages DNA and proteins by breaking bonds

• exposure is harmful to humans

  • to the radiation

  • irradiated foods are perfectly safe for consumption

• used to sterilize fruits, vegetables, meats

how does non-ionizing radiation work

• germicidal lamp at 254 nm

• doesnt penetrate solids or liquids very well

• damages DNA through the formation of pyrimidine dimers

• burns human skin

• generally used to sterilize air, water

examples of control that are effective against endospores

Physical and chemical methods such as autoclaving, dry heat, and certain disinfectants like hydrogen peroxide and bleach.

primary pathogens

can cause infection and disease in a healthy hot

• sometimes called a true pathogen

opportunistic

only causes infection and disease in non-healthy individuals or when introduces in a normally sterile party of the body

virulence

degree of pathogenicity of a parasitic microbe

virulence factors

• properties of a pathogen that allow it to successfully invade and cause disease in a host

primary habitant of a disease-causing organisms

phases of an infection

1.) entering the host

2.) attaching to the host

3.) invading and becoming established

1st phase of infection

• entering the host

• common portals of entry

  • skin and mucous membranes

  • GI tract

  • respiratory system

  • urogenital tract

  • pregnancy and birth

skin and mucous membranes 1st phase of infection

• usual entry points

  • damaged skin

  • mucosal membranes

• alternatives

  • enzymes that break skin barrier

  • bites

  • artificial damage

  • conjunctiva

GI tract 1st phase of infection

• must be ingested

• pathogens must have a mechanism to survive digestive enzymes and acidic pH of the stomach

• usually colonizes small or large intestines