control of microbes

8/8/2019 Control of Microbes

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Physical and Chemical Control of Microbes

I. Joseph ______ started _________ techniques with medicalapplications. By using carbolic acid (_______) -soaked rags andinstruments during and after surgery, gangrene and other infectionsfollowing surgery greatly diminished.

II. Terminology and Methods of ControlA. __________ means COMPLETE destruction of viruses and

microbes (including endospores) so that even if they are placedin a new growth medium, they will not revive or reproduce.

B. __________means to reduce the number of pathogens (includingviruses) until they are not a hazard, usually involving the use ofantimicrobial chemicals.

C. _____________ refers to removing toxins.D. __________ refers to a substantiallyreduced microbial population that meetsaccepted health standards.A clean appearance is expected!

Lister asepticphenol

Sterilization

Disinfection

SanitizationDecontamination


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E. Different situations warrant different levels of microbial control.1. daily life

Simple ___________with plain soap and water

is considered to be the single most important step inpreventing the spread of many infectious diseases!

handwashing

Sanitized items (not sterilized!!)


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2. hospitals

Danger of __________(hospital acquired) infections because of:

a. _________ condition of hospitalized patients

b. higher concentration of sick people with _________ microbes(*and many resistant forms!!)

c. _______ procedures (such as)

d. many health care workers are ______

e. lack of _______ care (handwashing

between patients, using gloves, etc.)

nosocomial

pathogenic

weakened

invasive

carriers

aseptic

3. microbiology/research/hospital laboratoriesmust use ________ techniquesa. Work surfaces should be ______.b. All media and instruments must be ______.c. Used ________ must be properly disposed of.

asepticclean

sterilecultures

surgery


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III. Selection of an antimicrobial procedure depends on many factorssuch as the type of _______, the extent of ____________,

____________ conditions, and potential risk of _________.

A. types of resistant microbes1. Bacillus and Clostridium can make ___________.

2. Mycobacterium has ______ cell walls.

3. ____________ is capable of metabolizing unusual

substances for food. (Like disinfectants!)

endospores

waxy

microbe contaminationenvironmental infection

Pseudomonas

B. the extent of contamination (size of the microbial population)1. Industry standard requires that ____% of the population is

killed with every __ minutes of exposure to the treatmenta. 100 microbes p 10 microbes p 1 microbe in __ minutesb. 1010 microbes p p p p p p p would take ___ minutes

SO, ________/_________ first helps reduce the populationbefore disinfection or sterilization.C. environmental conditions

1. _____________ (o heat o chemical action)2. _____3. ____, _______, _______, ______ can all block chemical action

90

2

4

20

washing scrubbing

temperaturepHdirt saliva blood feces


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D. Potential risk of infection

1. _______ items come into direct contact with body tissues.Critical

2. ____________ items come into contact with mucous membranes,but do not penetrate body tissues.

Semicritical

Surgical instruments

needles

Biopsy forceps

Respiratory equipment

Vaginalspeculum

Anal proctoscope


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3. ____________ items only touch keratinized skin surfaces.Noncritical

IV. Methods of Physical ControlA. ______ works by_________ cell proteins /enzymes.

It is the most common control method because it isfast, reliable, inexpensive & nontoxic.1. ______ heat

a. _______ 100C/10 minutes (kills most microbes& inactivates most viruses, but does not destroy__________).

Heat denaturing

MoistBoiling

endospores

stethoscope

Sphygmomanometer

(blood pressure cuff)


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Pasteurizationb. ____________: a brief heat treatment followed by rapid cooling.(Kills pathogens and reduces the number of spoilage organisms inmilk, juices, wine, beer: Does not sterilize!)

(1). LTLT (Low Temperature Long Term) 63C/30 minutes*(2). HTST (High Temperature Short Term) 72C/15 seconds

c. _________ (steam under pressure)(1). 15-20 psi/15-20 minutes/121C(2). ________ equipment, media, etc.(3). used in canning procedures to destroy

Clostridium botulinum __________!

Autoclave

Sterilizes

endospores


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2. ___ heat sterilizes.

a. Hot air ovens (160-170C/2-3 hours) used when ________ isundesirable.

b. ____________ (burning)

(1). _________/___________used to destroy disposable items,

soiled dressings, tissue specimens etc. @ 800C to 6500C

c. The hottest part of a Bunsen burner flame reaches 1,870C for______ during lab.

Dry

Incineration

flaming

Microbiologyis Fun!

moisture

furnaces incinerators


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B. Radiation (waves having energy but no mass) causes lethalchanges in DNA, denatures proteins, but doesnt reliably destroyendospores)!

1. Nonionizing rays = _____________radiationa. can be used to reduce the number

of organisms in air and on cleansurfaces

b. of limited use, cannot penetratematerials like cloth, glass, paper

2. Ionizing rays = ________ or _____________a. can be used to __________ items that are

heat or chemical sensitive, such as plasticsb. more effective, penetrates liquids and most

solids (used to treat Washington DC mail)c. In the US, radiation is approved to treatpork to prevent ___________, to treat beeffor ________ contamination and used totreat chicken for _________ contamination.

Ultraviolet (UV)

X-rays Gamma rayssterilize

trichinosisE. coli

Salmonella


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3. microwavesa. do not affect microbes directly, but may kill by _____ theygenerate

b. drawback is that microwave heating is ________

heat

uneven

C. Filtration (may be used for air, some heat sensitive materials suchas serum, vaccines, drugs, IV fluidsbeer/wine)

1. _____ ________ ________ ____ (HEPA) filtersremove airborne contaminants; used in operatingrooms, for people with allergies, etc.

2. In fluid filtration, _______ are separated from ________ bypassing through _______ with extremely fine poresa. Mechanical force or vacuum suction helps fluid through the filterb. does not sterilize unless pore size is small enough to trap

everything (smaller pores, o cost)

High-Efficiency Particulate Air

solids liquidsfilters


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V. Methods of ________ Control (* for heat sensitive items, largesurfaces)Destructive actions include injury to the cell _________,

denaturation of cell ________, inhibiting replication of _____.A. Disinfectants Vs Antiseptics

1. _____________ are chemicals used on inanimateobjects.

a. ___________ are chemicals that KILL/DESTROY germs.

(examples: fungicides, bactericides, viricides)

b. __________ refers to chemicals that donot kill, but prevent the growth of microbes.

(examples: bacteriostatic, fungistatic)2. __________ are disinfectants nontoxic

enough to be used on skin.

Chemical

membraneproteins DNA

Disinfectants

Germicides

Germistatic

Antiseptics


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B. Germicides are grouped according to their _______ (strength)

1. __________ destroy everything, including endospores(for sterilizing scalpels, respiratory therapy equipment,

proctoscopes, plastic Petri dishes, endoscopes)(ethylene oxide gas, hydrogen peroxide)

2. ____ level disinfectants (do not reliably destroyendospores) (used for GI endoscopes)(iodine, phenol, chlorhexidine, heavymetals such as silver nitrate)

3. ___________ level disinfectants (will kill Mycobacterium, but donot destroy all viruses or endospores, even with prolongedexposure) (used for stethoscopes, electrodes,

thermometers) (alcohols: ethyl alcohol, isopropyl)4. ____ level disinfectants (will not kill

Mycobacterium) (soaps, detergents)

High

Intermediate

Low

potency

Sterilants


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C. ______ _________ (5% Phenol is the standard against whichchemical agents are tested and compared)

1. Each chemical is compared for the same length of _____on the same _________ under ________ conditions

2. IF the chemical being tested requires a greater ____________or a longer ______ than phenol, its efficiency is _____ thanphenol.

IF the chemical being tested requires a lower concentration

or a shorter time than phenol, its efficiency is _______ thanphenol.

3. Ratio of: tested chemical activityphenol activity

< 1 means _____ efficient than phenol

> 1 means _____ efficient than phenol

Phenol coefficient

concentrationtime

greater

less

more

timeorganism identical

less


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D. Selecting the Appropriate germicidal chemical1. ________ (the benefit of disinfecting or sterilizing an item or

surface must be weighed against the risks associated with the useof that chemical) (hospital Vs home/office)

2. compatibility with the ________ being treated(metal, rubber, glass, plastic)

3. ________ may necessitate rinsing4. _____ and availability (bleach)5. ________ and stability (concentrates

require less space and store for longperiods, but when diluted/mixed, oftenhave limited shelf life)

6. _____________risk(safe disposal procedures needed)

Toxicity

material

ResidueCostStorage

Environmental


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VI. Methods used for Preservation (delaying spoilage) of PerishableProductsA. ________ preservatives (both nonfood and food)

1. organic ______ lower pH (inactivates enzymes, inhibits

growth, but does not always destroy microbes)2. ________ and _______inhibit germination of Clostridium

botulinum endospores!B. Low Temperatures

1. _____________

a. 0-10 C (___ C average)b. retards but does notprevent growth

2. ________a. ___ Cb. prevents growth but

does not kill allorganisms

Chemicalacids

nitrates nitrites

refrigerator

freezer

4

-20


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E. ____________ (freeze-drying)1. materials _______ frozen at temperatures well below 0C

2. vacuum while frozen to remove ________ (lightweight)3. biological cultures, medications, foods (expensive)

Lyophilizationrapidly

moisture

C. Increased _______ pressure by adding _____or _____; causes water to leave the cell, killing it.

D. ___________ (dehydration) of the material(natural [sun] or artificial)

osmotic saltsugar

Desiccation


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Elements of Chemotherapy

I. TerminologyA. ____________ = use of chemical agents to treat diseaseB. _______________ agent (CTA) = chemical agent used fortreatment of disease (even cancer)C. ___________ agent (AMA) = chemical agent used to treat

diseases caused by microbesII. Antimicrobial Agents

A. Types of antimicrobial agents1. _______ agents = metabolic products produced by

certain groups of fungi and fungal-like bacteria that areantibacterial in action

2. _________ agents = produced in the laboratory3. _____________ agents = derivatives of natural agents

altered in the laboratory by adding chemical groups toimprove effectiveness

ChemotherapyChemotherapeutic

Antimicrobial

Natural

Synthetic

Semi-synthetic


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B. Modes of action1. interfere with microbes chemosynthesis by inhibiting ________2. Disruption/interference with

a. of an essential metabolite by _________ inhibition(Sulfa drugs mimic PABA, blocking folic acid synthesis) (p. 77)

enzymes

competitive


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PABA

Folic acid

Competitive Inhibition


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b. by weakening/disrupting the bacterial cell ______

(Penicillin inhibits the enzyme that builds the amino acid cross-linkages of peptidoglycan) (p. 78)

enzymes

wall

Glycanbackbone


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c. by damaging the cell ___________ (Polymixin cleaves the

layers of the membrane like a knife) (p. 78)

membrane

hydrophilic

Amphipathic

enzymes

hydrophobic


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d. by inhibiting ________________ at 70s ribosomes (p. 79)(Erythromycin inhibits translocase, freezing the ribosome on

the mRNA.)(Tetracycline blocks tRNA attachment to mRNA)(Chloramphenicol inhibits transferase, preventing peptide

bond formation between amino acids.)

(Streptomycin causes a misreading of mRNA.)

protein synthesis

enzymes


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e. by inhibiting nucleic acid (______ and/or ____) synthesis(Antiviral: AZT inhibits reverse transcriptase.)(Antibacterial: Rifampin inhibits RNA polymerase.)(Antifungal: Griseofulvin inhibits RNA polymerase.)

DNA RNA


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2. ________ of activity = range of microbes inhibited or killed

a. ______spectrum usually effective against Gram+ and Gram-bacteria

(1). useful when no time to figure out exactly which microbe iscausing disease

(2). disadvantage is that it disrupts normal flora too (resulting in

_________ infections caused by opportunists).b. _______spectrum requires identification of the pathogen3. Tissue distribution, metabolism & excretion

a. ______ in body fluids (to be distributed in the blood)b. _______ in body fluids (so it is not broken down easily)

assuring constant and effective levels in the body (pH of

stomach may limit ____ administration unless coated)c. must be _________ by body tissues affectedd. _________ refers to the elimination rate of a drug

(this dictates the ___________ of dosage needed)

Spectrum

Broad

secondaryNarrow

Soluble

absorbed

Stable

Half-life

oral

frequency

C. Criteria that determine the effectiveness of antimicrobial agents1. ________ toxicity = destroys or inhibits microbe without

affecting host cellsSelective


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4. should be non __________ and not cause adverse reactions5. should be non __________ to reduce development of resistant

strains

D. Disadvantages of antimicrobial therapy1. ______ effects on normal tissues (especially liver &/or kidneys)2. disturb ____________3. ________ reactions4. development of __________ strains of bacteria, usually by

producing _________ that destroy AMA (such as penicillinase)a. _________ occur naturallyb. resistance genes on _________ that can be spread from

bacterial cells to other bacterial cells by ____________,______________, or ____________.

allergenicmutagenic

toxicnormal flora

Allergicresistant

enzymesmutations

plasmidsConjugation

TransformationTransduction


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F. AMA testing = _________________ method (p. 66)1. procedure

a. Inoculate a solid ______ of bacteria on agarb. Place paper disks saturated with various _________ on the

surfacec. ________24 hours and then observe

2. The principle behind this is that during incubation, the antibioticdiffuses into the agar and, if effective, ________ growth of thebacteria in its presence.

3. observations

a. _________________ (no growth around the disk means theAMA is effective)

b. _________ colonies are isolated colonies in the zone ofinhibition (They represent

________ cells from the originalpopulation!)

inhibits

Zone of inhibition

Satellite

Location ofsatellite coloniesif present

resistant

Overlapping antibiotics (withsynergistic effects) may be needed

if satellite colonies appear.

disk-plate diffusion

lawn

antibiotics

Incubate

control of microbes

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