control of microorganism
TRANSCRIPT
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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.