Control of Microorganism

7/28/2019 Control of Microorganism

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CONTROL

OF

MICRO ORGANSIMDISINFECTION AND STERILIZATION


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Objectives

Differentiate the functions and purposes of adisinfectant and antisepticDescribe the mechanism of action of eachtype of chemical agentDescribe the different heat methods and theirrespective applications

Give the general modes of antimicrobialaction


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Sterilization versus Disinfection

Sterilization refers to the completedestruction of all forms of life includingbacterial spores.


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Joseph Lister introduced the concept of asepticsurgery.


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Sterilization versus Disinfection

Disinfection- refers to a process thateliminates a defined scope of microorganismincluding some spores.

Most disinfectant are chemical agentsapplied to inanimate objects.

Antiseptic- a substance applied to the skinfor the purpose of eliminating or reducing thenumber of bacteria present.


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Factors that influence the Degree

of KillingTypes of organismsNumber of OrganismsConcentrations of Disinfectant

Presenc of Organic materialsNature of Surfaces to be DisinfectedContact timeTemperaturePH

BiofilmsCompatibility of Disinfectants and sterilants


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Types of Organisms

Organisms vary greatly in their ability towithstand chemical and physical treatment

Prions- most resistant to actions of heat,chemicals and radiation.- naked pieces of proteins, similar to avirus but without nucleic acid

Can withstand temperatures exceeding121 degrees celsius.


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prionsprions

Bacterialspo

resBacter

ialspores

Mycoba

cteriaMycobacteria

NonLipidVi

rusesNonL

ipidViruses

BacteriaBacteria

LipidVirusesLipidViruses

Most resistantMost resistant

Least resistantLeast resistant


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Number of Organisms

Microbial Load( BIOBURDEN)- total number

of organisms present

In general, the higher the numbers oforganisms requires longer exposure


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5 10 15 20 25 30 35 405 10 15 20 25 30 35 40

120

110

100

90

80

60

50

40

30

20

120

110

100

90

80

60

50

40

30

20


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Concentration of Disinfectant

The amount of disinfectant needed to destroymicroorganisms varies with the differentagents

Manufacturer's instructions on preparation,dilution, and used must be followed carefullyProper concentartions of disinfecting agentsensure the inactivation of target organisms

and promotes safe and cost effectivepractices


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Presence of Organic Material

Organic Materials such as blood, mucus andpus affects killing activity by inactivating the

disinfecting agents.

For optimal killing activity, instruments andsurfaces should be cleansed of excess

organic material before disinfection.


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Nature of Surfaces to beDisinfected

Certain medical instruments aremanufactured of biomaterials that exclude theuse of certain disinfection or sterilizationmethods because of possible damage to theinstruments


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Contact Time

The amount of time a disinfectant or sterilantis in contact with the object is critical.

The killing action of any disinfectant is never

instantaneous. Therefore enough exposuretime should be given for the purpose.

The amount of time that an agent is incontact with an object can also determinewhether it is disinfecting or sterilizing.


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Temperature

Disinfectants are generally used at room

tempearture (20C to 22 C)

Activity is increased by an increase intemperature or decreased in temperature


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pH

The pH of the material to be disinfected orsterilized can have an effect on the activity ofthe disinfecting or sterilizing agent.

It is critical to make sure at what pH the agentis active and what pH of the material to beexposed to the agent is at the time theprocess will be done.


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Biofilms

Biofilms can be considered as a communityof bacteria or other microorganisms.

The presence of biofilms will makedisinfection more difficult.

To disinfect materials with biofilms present,

the concentartion need to be increased andthe contact time may need to be increased.


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Compatibility if Disinfectants

A common mistake is to believe that twodisinfectants are better than one.

When more than one disinfectant is used, thecompatibility of the disinfectant must betaken into consideration.


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Methods of Disinefection andSterilization

E. H Spaulding categorized medical materialsinto three device classification

1. Critical materials2. Semicritical Materials3. Non critical Materials


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Critical Materials- are those that invade sterile

tissues or enter the vascular system.- most likely to produce infection ifcontaminated and therefore requiressterilization.

Semicritical Materials require high level ofdisinfection.

Noncritical Materials require intermediatelevel to low level disinfection


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Control of Microorganisms using Heat Methods

Method Temperature(celsius)

Time required Applications

Boiling Water 100 15 minutes Kills microbialvegetattive forms;endospores survive

Autoclave(Steamunder pressure)

121.6 15 minutes at 15 psi Sterilize and killsendospores

Oven(Dry Heat) 160-180 1.5- 3 hours Sterilizes; keepsmaterial dry

PasteurizationBatch Method

Flash method

63

72

15 seconds

15 seconds

Disinfects and killsmilk bornepathogens andvegetative forms,endospores survive

Same but shortertime at highertemperature


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Filtration

Maybe used with both liquid and air.

Filtrations of liqiuds is accomplished throughthe use of thin membrane filters composed of

plastic polymers or cellulose estrescontaining pores of a certain size.

Filtrations of air is accomplished with the use

of HEPA filter.-able to remove larger than 0.3 um

microorganism


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Radiation

Two forms of Radiation

1. Ionizing radiation-gamma rays, electronBeams, short wavelength and high energy

- used by medical industry for sterilizationof disposable supplies

2. Non Ionizing radiation- UV light, longwavelenth and low energy.

-poor penetrability;limited usage.


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Chemical Methods

Chemical Agents exert their killing effects bythe following mechanism:

1. Reaction with components of the

cytoplasmic membrane2. Denaturation of cellular proteins3. reaction with the thiol(-SH) groups of

enzymes

4. Damage of RNA and DNA


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Thegerm theorygerm theoryof disease was one of themost important contributions by the scientificcommunity of microbiologist to the general

welfare of the worldwide population.

Ignatz Semmelweis ( 1816-1865) andJoseph Lister(1827-1912) are considered to

be important pioneers for the promotion ofasepsis.

Disinfectants and Antiseptics


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Hygienic Handwashing andWaterless Handrubs

The main goal of handwashing is to eliminatethe transient flora.Transient Flora is

contracted from the environment or fromother people .In most cases, these organism

are not part of the established normalbiota.biota.


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Although transient organism are easily

removed from the upper layer of the skinalong with dirt particles and oil, they maybecome part of the resident established flora

of individuals.

Interventions against the bacterial load of thehands should balance two goals:

protecting the skin with its resident flora and

killing the transient flora.


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Routine handwashing procedurein health care settings:

Removing physical dirt(including blood,excretions,secretions or discharge from

lesions)Before and after routine patient contact.

After contact with infected or colonizedpatients or their immediate surroundings.


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In high-risk units such as intensive care andburn units.

On entering protective isolation units and

leaving source isolation units.

Before antiseptic procedure(e.g., dressingtechniques, minor invasive procedures)


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Waterless handrubs(alcohol handrubs)-either liquid or gel- are used for hygeinic hand

antiseptics.

They can also be used as an alternative toroutine handwashing when there is no visible

soiling and for patient contacts.

They are often more convenient thanhandwashing and can be particularly useful ifsinks are not readily available.


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The technique involves rubbing small amountportions (3 to 5 mL) of a fast-acting antiseptic,usually an alcoholic preparation into thehands and rubbing until dry or for a preset

duration recommended by the manufacturer.

All areas of the hands must be coveredcompletely with the antiseptic, including the

subungual spaces of the fingers.


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Surgical Hand Scrub andWaterless Surgical Handrubs

ObjectivesTo eliminate the transient flora and most ofthe resident flora.

Resident flora can be persistently isolatedfrom the hands of most people.Theseorganism include coagulase-negative

staphylococci, Corynebacterium spp.(diphtheriods or corynefforms),Propionibacterium spp., and Acinetobacterspp.


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A surgical hand scrub drug product is definedas an antiseptic containing a preparation that

significantly reduces the number ofmicroorganisms on intact skin; it is broad

spectrum, fast acting, and persistent.


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Presurgical Skin Disinfection

In order to be effective, preoperative skinpreparation formulations must degerm an

intended surgical site rapidly as well asprovide a high level of bacterial inactivationand persistent antimicrobial activity, up to 6

hours after preparing the skin


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Points to Remember


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Physical and chemical methods may used in theprocess of sterilization in order to remove all

forms of life.

Disinfection involves removal of pathogenicorganisms but may not include removal of

bacterial or other spores, and most disinfectantsare chemical agents.

Factors that influence the degree of killing

include the types of organisms, number ororganisms present,concentration of disinfectingagent, amount of oil present, and the nature ofthe surface to be disinfected.


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Antiseptics are designed to reduce the bacterial

load of living tissues.

Disinfectants are designed to be used oninanimate objects to kill or destroy disease-

producing microorganisms.

Antimicrobial agents for health care personneluse must meet certain standards that

demonstrate the product's safety and afficacy.

Documents

Control of Microorganism