Exam2: Microbio B2

sterilization

the removal of all microbial life from an object/surface

disinfection

the removal of common harmful bacteria (but not endospores)

antisepsis

• type of disinfection

• disinfection of living tissue

sanitization

• type of disinfection

• cleaning to remove debris, soil, microbes, and other materials to reduce risk of infection

the 2 different approaches to sterilization and disinfection

• microbicidal

• microbistatic

microbicidal

kill the microbes

microbistatic

stops the microbes from growing

patterns of microbial death

• microorganisms are not killed instantly

• population death usually occurs exponentially

• microorganisms are considered to be dead when they are unable to reproduce in conditions that normally support their reproduction

effectiveness factors of microbes surroundings impacting their survival

• population size

• population composition

• concentration or intensity of antimicrobial agent

• duration of exposure

• temperature

• local environment

microbial control methods

• physical agents

• mechanical removal

• chemical agents

microbial modes of action

• disrupt cell walls

• disrupt cell membranes

• affect protein/nucleic acid synthesis’

• alter protein functions

physical methods

• heat (moist and dry)

• cold

• desiccation

• radiation

• filtration

moist heat

• type of physical method

• denatures proteins and degrades DNA

  • boiling water is a good technique for disinfecting

    • most bacteria, parasites, and viruses are killed quickly by boiling water

    • a few are not and can survive hours in boiling water

  • sterilization requires higher temperatures

autoclave

• moist heat in which sterilization requires higher temperatures

  • ____increases the temp to 121 degrees C

  • even endospores will be killed in 15 minutes

dry heat

• type of physical method

• oxidizes (or incinerates) microbes

  • no worries about pressure so higher temp can be used

  • has to work longer since heat is transferred slower by air than moisture

• air or light radiation

sterilizing dry heat

oven = 2-3 hours @ 160 degrees C

thermal death time (TDT)

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

thermal death point (TDP)

lowest temperature required to kill all test microbes in 10 minutes

Pasteurization

the process of heating at a moderately high temp or for short time so the food isn’t destroyed

• kills off or reduces the bacterial population of a particular microbe

• prolongs the lifespan of a food product, but it isn’t sterile

low temperatures (cold)

• type of physical method

• slow or stop growth by lowering temp

  • freezing

  • refrigeration

freezing

• type of low temp method

• -20C or lower

• stops growth, no liquid water

• some cell death from ice crystals disrupting membranes

• not a reliable disinfectant

refrigeration

• type of low temp method

• 4C

• greatly slows growth of most organisms

• food keeps much longer

• some pathogens are psychrophiles and continue growing

desiccation

• type of physical method

• the removal of all liquid water

  • some microbes (particularly gram negative) will be killed

  • other microbes are actually preserved and live longer when desiccated

lyophilization

• type of desiccation

• rapid drying and freezing of bacterial sample

• commonly used to preserve bacteria for long-term storage

ionizing radiation

• type of radiation physical method

• x-rays and gamma rays

  • damages DNA (more severe)

  • some can pass right through most substances

  • possible to sterilize items inside and out

  • effective against endospores

  • not always effective against viruses

ultraviolet (UV) radiation

• type of radiation physical method

• damages DNA (less severe)

• little penetrating power

• effective against endospores

• useful for disinfecting the air or outer surfaces

• can reduce microbes in water

types of radiation physical methods

• ionizing

• ultraviolet

filtration

• type of physical method

• separates microbes from a solution or from the air

  • air or water is sucked through a filter with very small holes; microbes are too big to pass through

  • liquids can be completely sterilized

  • also used to disinfect air coming into clean rooms

filters can disinfect if pores are..

large

filters can sterilize if pores are..

small

phenols

• common chemical disinfectant

• the original disinfectant used by Joseph Lister

mechanism of phenols

break down lipid-containing structures

• plasma membrane

• the waxy cell wall of Myobacterium

pros/cons of phenols

pros:

• stable

• works around other organic compounds

• kills tubercular bacteria

cons:

• stinky

• irritating to the skin

• potentially toxic

• have been replaced (don’t use anymore)

halogens

• type of common chemical disinfectant

• iodine, chlorine, fluorine, bromine

halogens mechanism

disrupts protein function

iodine

• a halogen

• effective against all kinds of bacteria and many viruses

chlorine

• halogen

• can be used as a gas or as a salt to disinfect surfaces or water

hypochlorites (chloring, bleach)

• halogen

• used as an aqueous (dissolved in water) solution

pros/cons for halogen

pro:

• effective against variety of pathogens

cons

• toxic @ high levels

• inactive by light, high pH, excessive organic matter

iodine tinctures

• a mix of alcohol and iodine

• historically have been used to disinfect skin prior to procedures

• some patients have strong reaction to ___

• may have neurological effects on newborns

chlorhexidine

• a phenolic derivative

• rapidly replacing it as an antiseptic

alcohol

• type of common chemical disinfectant

• most effective when mixed with water (70:30 mix)

• often works to enhance the activity of other disinfectants

alcohol mechanism

• denatures proteins and disrupts membranes

• helps mechanical removal of microbes and dirt

pros/cons of alcohol

pros:

• evaporates rapidly

• leaving no residue after use

cons:

• some bacteria and many viruses are resistant

• little effect on endospores

heavy metals

• type of common chemical disinfectant

• mercury, copper, silver

• silver nitrate

• bandages and catheters with silver in them are coming into use; effective against antibiotic resistant

mercury, copper, silver (heavy metal)

small amounts can kill bacteria in heavy metals

silver nitrate (heavy metals)

heavy metals: (1%) solution used to be placed in the eyes of newborns to prevent infection

heavy metal mechanism

denatures or inhibits proteins

pros/cons of heavy metals

pros:

• effective with small amounts of metal

• very stable

cons:

• can be toxic

• very stable

surface-active agents (surfactants)

• type of common chemical disinfectant

• soap/detergent: some antiseptic properties

• cationic detergents (positively charged) are more effective

• quaternary ammonium compounds (quats)

surface-active agents (surfactants) mechanism

disrupts membranes and cell walls, also good sanitizers

pros/cons of surface-active (surfactants)

pro:

• non-toxic

cons:

• multiple dangerous microbes are highly resistant to surfactants

sterilant gases

• type of common chemical disinfectant

• ethylene oxide

• propylene oxide

• germicide, sporicide, highly effective

• used to sterilize heat-sensitive medical equipment

sterilant gases mechanism

denatures proteins and damages DNA

pros/cons of sterilant gases

pro

• powerful sterilant with potent sporicidal activity

cons

• toxic

• highly explosive

aldehydes (CHO functional group)

• type of common chemical disinfectant

• formaldehyde

• glutaraldehyde

• strong sterilant but highly toxic

• some weak aldehydes can be used as disinfectants

mechanism for aldehydes

denatures proteins

pros/cons for aldehydes

pros:

• incredibly

• effective germicides

• can actually sterilize

cons:

• highly toxic

• carcinogen

oxidizing agents

• type of common chemical disinfectant

• ozone

  • can substitute for chlorine to disinfect water

• hydrogen peroxide (H2O2) liquid or gas

  • good at disinfecting non-living surfaces (sporicide)

  • some use as an antiseptic, but may cause damage

  • particularly good vs. anaerobes

  • vaporized gas used on medical equipment

oxidizing agents mechanism

altered protein function

DNA damage

pros/cons of oxidizing agents

pros

• strong germicides, sporcicides

cons:

• unstable, can cause tissue damage

acids

• type of common chemical disinfectant

• corrosive and toxic, most are rarely used

• organic ___: lactic, acetic, propionic

• used as preservatives to keep food from spoiling

• safe to eat; restricts growth of common food spoilage microbes

alkaline agents

type of common chemical disinfectant

ammonium hydroxide, sodium hydroxide

• used as cleansing agents

• one of only agents with activity against prions

acids/alkaline agents mechanism

denature proteins

cons of acids/alkaline agents

irritating and potentially damaging to skin, wounds

chemotherapy

treatment of a disease with chemicals

antimicrobials

chemicals that kill microbes

• selective toxicity

selective toxicity

kills microbes better than it kills us

antibiotics

• are antimicrobial chemicals that are produced by another microbe

• sometimes affects us too

  • physiology

  • kill off our native flora (bacteria)

therapeutic index

• measure of selective toxicity

• formula: toxic dose/effective

toxic dose

• dose at which a patient shows side-effects

• different therapeutic index for different side-effects

effective dose

• the dose at which the disease is cured by the drug

antibiotics spectrum

how specific is the anitbiotic?

• broad

• narrow

broad spectrum

• spectrum of antibiotics

• kills many different genera of bacteria

narrow spectrum

• spectrum of antibiotics

• kills one or a few genera or species of bacteria

bactericidal

• causes bacterial cells to die by doing permanent damage

• most require that bacteria are growing/dividing to work

bacteriostatic

• causes bacterial cells to stop growing/dividing

• damage is reversible, removal = resume growth

• allows immune system to gain an advantage

when to use bactericidal

• infection where host defenses are useless

  • tough bacteria (anthrax)

  • immune compromised

when to use bacteriostatic

• if the therapeutic index is better

• resistance to bactericidal options

• protein synthesis inhibitors which stops exotoxin production

penicillin

• antibiotic for cell wall synthesis inhibitor

• first generation of ___ didn’t work against gram negatives

  • couldn’t get through outer membrane

  • altered the structure so it can get through

• usually bactericidal

  • cells lyse from osmotic pressure

cell wall synthesis inhibitors mechanism

blocks synthesis of peptidoglycan cell walls which depends on growth

polymyxins

• cell membrane inhibitor

• chemicals disrupt cell membranes, particularly effective against gram negative bacteria

• usually bactericidal

  • cells lyse from membrane disruption

  • effective even against non-growing cells

Ciprofloxacin (cipro)

• DNA replication inhibitors

• bactericidal

• blocks unwinding of DNA double strands

• requires growth to do damage

Tetracyclin

• protein synthesis inhibitor

• bacteriostatic

  • binds reversibly to the ribosomes

  • selective for bacterial ribosomes, not humans

streptomycin

• protein synthesis inhibitor

• bactericidal

  • binds irreversibly to the ribosomes

  • needs oxygen to be taken up

    • little effect on gut flora

sulfa drugs

• metabolism inhibitor

• bacteriostatic

• act as competitive inhibitors for the enzyme that converts PABA into folate, needed for DNA synthesis

antibiotic resistance acquired with mutations

when other bacteria acquire resistance from new genes/mutations arise spontaneously in the population

antibiotic resistance acquired with genetic transfer

when other bacteria acquire resistance from new genes/mutations by picking up resistance from other bacteria

“keep it out”

• antibiotic resistance mechanism

• mutate the transport proteins

“break it down”

• antibiotic resistance mechanism

• enzymes that degrade the antibiotic

“change the target”

• antibiotic resistance mechanism

• mutate the target proteins so the antibiotic no longer works