Recent advances in sterilization

Recent Advances in Sterilization & Disinfectant

Dr R Sathyajith

Recent Advances in Sterilization

• Sterilization, as a specific discipline, has been with us for approximately 120 years, since the invention of the steam autoclave by Charles Chamberland in 1879

• We have seen progressive refinement in steam sterilizers: from the early, manually operated equipment to modern microprocessor-controlled, automatic machines.

• Although the efficiency, reliability, and performance monitoring of modern equipment is continually improving, the fundamental process remains essentially the same.

Plasma Sterilization

• Sterilization is defined as any process that destroys all micro-organisms

• Conventional methods (autoclaving and ethylene oxide fumigation), though proven effective, do have their disadvantages such as long sterilization times, tenuous operating conditions and lack of versatility.

• Plasma sterilization is fast evolving into a promising alternative to standard sterilizing techniques.


• Research on plasma sterilization started way back in 1960. Since then, extensive studies are being performed.

• Not future technology! Plasmas are used today!

• Plasmas are currently employed in many industries to accomplish both highly effective, and delicate sterilization.


First discovered by Sir William Crookes, in 1879 But it wasn’t called “plasma” until 1928, when Irving Langmuir coined the term.


Plasma Sterilization• Plasma is basically ionized gas. When you

apply an electric field to a gas, it gets ionized into electrons and ions.

• Plasma is usually comprised of UV photons, ions, electrons and neutrals.

• A plasma is a quasi-neutral collection capable of collective behavior

• Their combined photolytic, chemical and electric action efficiently kills most micro-organisms.



• Electrical Plasma, used in sterilization, can be classified into two types broadly:

Volume plasma & Surface plasma.

Plasma Sterilization• Initial literature that worked on establishing

plasma sterilization as a safe, viable method of sterilization used mostly volume plasma generated from gases such as He, N2, O2.

• However recent literature has started leaning towards using Dielectric Barrier Discharge (DBD) Plasma, which is surface plasma.

Volume Plasma

• Plasma is classified as volume plasma when it is generated by injecting a gas at a specific flow rate into a chamber fitted with electrodes and grounded sufficiently.

• When the circuit was closed, the gas inside the chamber would be subjected to an electric field and hence ionized, creating plasma.

Volume Plasma

• Most of the research in plasma sterilization pertains to volume discharge. Triphasic behavior was observed in these experiments.

UV irradiationPhoto-desorptionChemical etching

Surface Plasma

• Surface plasma is usually when the electrodes (power & ground) are embedded into a dielectric and hence plasma is generated on the surface of the dielectric itself.

• DBD discharge is generated between two electrodes with a dielectric barrier in between them, about a few mm is a surface plasma.

Methods

• Dielectric Discharge Barrier (DBD)• Inductively Coupled Plasmas (ICP)• Atmospheric Pressure Plasma Jet (AAPJ)• Microwave (MW) Plasmas

• MW plasma most effective• All methods < 10 min treatment time

(much less than conventional methods!)


• Plasma sterilization operates synergistically via three mechanisms:

Free radicals interactionsUV/VUV radiative effectsVolatilization

Plasma - Volatilization

• It is able to vaporize microbiological matter, causing physical destruction of spores.

• The spores are basically made up of simple atoms like C, O, N, H etc.

• Charged particles react with cellular atoms/chemical bonds of microbiological layer to form gaseous compounds.

• When the organism loses such atoms that are intrinsic to its survival, it dies

Plasma - UV

• UV/VUV radiation causes1.Formation of thymine dimers in DNA,

inhibiting bacterial replication.2.Base damage3.Strand breaks


Plasma - Mechanism

• Damaged DNA/RNA causes microbial death by 4 mechanisms:

1.Apoptosis – Nucleus programmed to shrink and cause cell to commit suicide.

2.Autophagy3.Necrosis4.Mitotic Catastrophe – radiation causes

mis-segregation of chromosomes, leading to Apoptosis

Why Plasma sterilization?• The process is usually at room

temperature and hence poses no dangers associated with high temperatures (unlike autoclaves)

• Doesn’t involve any chemicals and hence is non-toxic (unlike EtOH)

• Time of treatment is fast and of the order of 1 min or less.

• Is versatile and can sterilize almost any material and any shape

Disadvantages of Plasma Sterilization

• Weak penetrating power of the plasma. Complications arise in:

Presence of organic residuePackaging materialComplex geometriesBulk sterilization of many devices• Solutions: Introduce preferentially

targeting UV/VUV radiation of proper wavelength

Disadvantages of Plasma Sterilization

• Cannot be used on paper, cellulose or linen

• Can corrode certain materials• Inability to process liquids, powders, or

strong absorbers (cellulosics)• Lumen restrictions

Gas Plasma• Low-Temperature Hydrogen Peroxide Gas

Plasma (LTHPGP)• Gas Plasma (vaporized hydrogen

peroxide) is a relatively new option that can provide low heat sterility cycles with none of the off-gassing concerns present with EtO.

• Gas plasma sterilization technology based of Plasma was patented in 1987, and marketed in US 1993.

Gas Plasma - Steps

• The Vacuum PhaseThe chamber is evacuated, reducing

internal pressure in preparation for the subsequent reaction.

• The Injection PhaseA measured amount of liquid peroxide is

injected into the chamber, evaporating the aqueous hydrogen peroxide solution and dispersing it into the chamber, where it kills bacteria on any surface it can reach.

Gas Plasma - Steps

• The Diffusion PhaseThe hydrogen peroxide vapor permeates

the chamber, exposing all load surfaces to the Sterilant and rapidly sterilizes devices and materials without leaving any toxic residues. At the completion of this phase, the chamber pressure is reduced and the plasma discharge is initiated.

Gas Plasma - Steps

• The Plasma PhaseAn electromagnetic field is created in

which the hydrogen peroxide vapour breaks apart, producing a low-temperature plasma cloud that contains ultraviolet light and free radicals. Following the reaction, the activated components lose their high energy and recombine to form oxygen and water.

Gas Plasma - Steps

• Phases 1, 2, and 3 are then run a second time for added efficacy. This built-in reprocessing assures optimal sterilization for even the most difficult-to-sterilize devices.

• The Vent PhaseThe chamber is vented to equalize the

pressure enabling the chamber door to be opened. There is no need for aeration or cool-down. Devices are ready for immediate use.

Gas Plasma• The Sterrad system offers a short cycle (averaging 75 minutes), low temperature and humidity, no aeration requirement, no chemical residues, negligible environmental impact, and wide compatibility with materials. Its drawback is an inability to process

liquids, powders, or strong absorbers (e.g., cellulosics).

Gas Plasma - STERRAD

Gas Plasma

• The Biological indicator used with system is Bacillus atrophaeus spores and Bacillus sterothermophilis.

• The newer version of Sterrad, which employs a new vaporization system that removes most of the water from hydrogen peroxide, has a cycle time from 28-38 minutes.

Gas Plasma - Prions

• The effectiveness of low-temperature STERRAD® technology against the prion threat confirmed that it is possible to eliminate these deadly pathogens while helping to preserve the integrity of medical devices, including heat sensitive surgical instruments

Plasma - Current Research

• The fundamental underlying physics in the process of plasma sterilization is to a large extent not understood.

• Sporadic research efforts & a lot of conflicting opinions

Importance of UV photons over neutrals Failure criterion

Plasma - Current Research

• To harness the ability of plasma sterilization to produce fast, easy, non-toxic sterilization that can be applied to a wide variety of materials

• Major challengeHuge amount of power that goes into

operating these devices (voltages of 12 kV)

Pulsed light sterilization


• Pulsed light is a non-thermal sterilization method that uses brief intense pulses or flashes of white light to kill micro-organisms.

• The basic principle of Pulsed Light sterilization is to destruct microorganisms with short intense light flashes generated by Xenon lamps.

Pulsed light sterilization• Energy, needed for product decontamination is

accumulated in a capacitor.• A high-voltage signal initiates the so called ‘arc

formation’.• An ‘arc’ is highly ionized gas with strong

currents. Xenon gas is used, because of its capacity to convert electrical energy into light energy. This arc starts the flash of intense luminosity.

• The peak power of one flash is around 1 megawatt.


• The flashes present a continuous spectrum, rich in UV light that lasts a few hundred of microseconds.

• The housing of the lamp is made of quartz, so almost no optical energy is wasted.

• The flashes are controlled and concentrated by aluminum reflectors, specifically designed for each application.


• Each flash produces an enormous amount of energy. With a lamp energy of 300 J and a flash time of 0.3 mS that’s 1Mwatt. Or, 1 kW per square cm of the treated object.

• The microorganisms absorb all the energy, mainly that of the further UV domain.

Pulsed light sterilization• Pulsed light has a complete destructive effect on

microorganisms, a combination of two phenomenon :

Sterilizing effect of UV : the DNA in the cells of microorganisms absorbs the UV rays. This ruptures the double strands of DNA and provokes the formation of abnormal single-strand bonds. This prevents DNA replication. The microorganism’s protein production and cell metabolism is blocked: and it dies.

Power of the flash : intense energy delivered in a very short time increases this lethal effect.

Pulsed light sterilization• The pulsed UV light causes formation of

Pyrimidine dimers in DNA, resulting in genetic damage to cells and their ultimate destruction. Types of damage induced by pulsed UV light are:

Photolysis Loss of colony-forming ability Inability to support phage growth (enzyme

inactivation) Destruction of nucleic acid.


Pulsed light sterilization - CLARANOR

1. Electronics bay: powered by the main current it generates the electrical pulses. The integrated cooling system regulates the temperature of the water in the lamp circuit.

2. Optical cavity: here the light is generated, powered by the electronic bay. It has flash lamps associated to the reflector that focusses the light towards the surface that needs to be treated.

Pulsed light sterilization - Benefits• The most important reasons for considering pulsed

UV light systems for sterilization are:

Total DNA destructionSafety - No mercury, VOC Inline productionTemperature integrity Process effectiveness Process speed - 1-3 pulses 6log reductionProcess flexibility Free of toxic substances Worker-friendly (safe and easy to use) Minimum space requirements


• Pulse light sterilization technology has a promising application potential in areas requiring a high level of sterilization without residual problems and without heat application and contact.

Hydroclave

Hydroclave• Newer regulations (Environmental and

Medical Waste Regulations) require a non-incineration technology, which is easy and safe to operate & has no harmful emissions & also sterilizes at low cost.

• Hydroclave offers a remarkably simple, affordable, patented, proven medical/Infectious waste treatment process which achieves the highest waste sterility, at an incredibly low treatment cost.

Why Hydroclave?

• PerformanceGuaranteed high level of sterilization,

including wet waste, metals, liquids and sharps.

Automatic operation, and not dependent on operator skill for sterility.

No infectious or harmful emissions.Mechanical destruction of the waste, and

safe for land-fill.

Why Hydroclave?

• EconomicLow operating cost with low energy

consumption.Low maintenance costs.No costly bags, filters or chemicals in the

process.Very large weight and volume reduction of

the waste.

• Medical Waste is deposited in the Hydroclave vessel.

• The Hydroclave can process:

Bagged waste, in ordinary bags

Sharps containers Liquid containers Cardboard

containers Metal objects

The Hydroclave Process – Stage one

The Hydroclave Process – Stage two

1. Powerful rotators mix the waste and breaks it into small pieces.

2. Steam fills the double wall (jacket) of the vessel and heats the vessel interior.

3. The liquids in the waste turn to steam.

4. After 20 minutes the waste and liquids are sterile.

The waste fragmentation and sterilization

The Hydroclave Process – Stage three

1. The vent is opened, and the vessel de-pressurizes.

2. Steam heat and mixing continue until all the liquids are evaporated and the waste is dry.

Vessel venting and dehydration

A. The unloading door is opened.

B. The mixer now rotates in the opposite direction, so angled blades on the mixer can push the waste out the unloading door.

C. The dry, sterile waste can be fine-shredded further or dropped in a waste disposal bin.

The Hydroclave Process – Stage fourUnloading the Waste - The waste is now ready for safe disposal!

Dry waste, regardless of its

original water content.

Low odor, due to the dryness.

Volume reduction to 85%

Weight reduction to 70%

Accepted as harmless waste

Sterility of 6log10 achieved

sterility under any waste load

conditions – even high liquid

load.

The Hydroclave Result

Hydroclave of Needles & Sharps

• The Hydroclave achieves a high degree of sterility due to a vigorous mixing and fragmenting of the waste inside the hot vessel:– it breaks apart the sharps container …– sets free the sharps into the vessel …– where they are thoroughly exposed to the

required temperature and pressure.

• It is IMPOSSIBLE for a needle or sharp to be shielded from the temperature as there are no “cold spots”, assuring total sterility.

Hydroclave of Needles & Sharps• If for any reason temperature and pressure

parameters are not met, the Hydroclave automatically resets and initiates a repeat sterilization cycle.

• How does the Hydroclave achieve the high sterility?

By a vigorous mixing and fragmenting of the waste inside the hot vessel.

• How does the Hydroclave make the waste very dry?

By applying dry heat from the jacket to the waste, instead of injecting hot, wet steam into the waste.

Hydroclave vs Autoclave

• Hydroclave• Low operating cost by

recycling steam.• No special bags required• Treats wet or liquid loads

easily• Strong weight reduction• Strong volume reduction• Consistent high sterility

•Autoclave• Higher operating cost, no steam recycling

• High temp/ bags req’d• Cannot treat wet or liquid loads• Weight increase• No volume reduction• Spotty sterility

Tata Memorial Hospital 1999-2001

This unit ran 2,200 cycles, has treated 88,000 Kg of medical waste, and never failed a sterility test on any cycle.Downtime was less than 1%, and maintenance cost minimal

Washer - Disinfector

Washer - Disinfector• Washer disinfectors have a double function First a thorough cleaning process using water ,

detergents & enzymes followed by Heat disinfection where the water temperature

is elevated almost to boiling point.

• Another key feature of washer-disinfectors is the extremely high flow of water, in terms of both volume and pressure

The massive flow of water spraying all items in the washer-disinfection process results in very effective physical (mechanical) cleaning.

Washer – Disinfector Warning

• Not intended or recommend that Washer/Disinfector be used for the terminal disinfection or sterilization of any regulated medical device.

• Washers/ Disinfectors are intended only to perform an initial step in the processing of soiled, reusable medical devices.

• If medical devices will be contacting blood or compromised tissues, such devices must be terminally processed.


• Washer/Disinfector is intended for use in the cleaning and disinfecting of reusable utensils, trays, glassware, bedpans and urinals.

• It can also be used for rubber and plastic goods, simple hard-surfaced rigid surgical instruments, such as forceps and clamps, and other similar and related articles found in healthcare facilities.


• Different default cycle modes• Customizable modes also available• Three injection pumps are provided with a

standard washer/disinfector.One enzyme pump,One detergent pumpOne lubricant pump (for Thermal Rinse

phase)


• Each preprogrammed cycle is equipped with

Pre-WashEnzyme WashRinseThermal Rinse phases



• Pre-WashCold water enters the sump from the

building supply.Once the sump fills, pre-wash water is

recirculated and sprayed over the load for two minutes (factory-setting).

On completion of the phase, water is sent to the drain.

Recirculation time is adjustable from 15 seconds to15 minutes

Washer - Disinfector• Pulsed EnzymeHot tap water enters sump from the building

supply, where a selected amount of enzyme detergent is added automatically.

The load is sprayed with enzyme solution for 4.0 seconds, then allowed to soak on instruments for 26 seconds. Spray/soak pattern is repeated for the selected time interval (4.0 to 15 minutes).

On completion of the phase, the solution is sent to drain, and the load is rinsed with hot water.

Washer - Disinfector• WashHot tap water enters the sump from the building

supply, where a selected amount of detergent is added automatically.

Detergent solution is heated and maintained at a temperature ranging from 140 to 180F (60 to 82C)

Once set temperature is reached, solution is recirculated and sprayed over the load for the selected time interval (2.0 to 15 minutes).

On completion of the phase, the solution is sent to the drain.


• Neutralizer & RinseWater enters & may be heated and

maintained at a 110 to 180F (43 to 82C) for 15 seconds.

Once the sump fills, rinse water is recirculated and sprayed over the load for the selected time interval (15 seconds to 15 minutes).

On completion of the phase, water is sent to the drain.


• HEPA-Filtered DryingHot air is recirculated over the load for 6 to

60 minutes at low temperature (180F/82C), or 6 to 30 minutes at high temperature (240F /116C).

During the Drying phase, a small quantity of air is exhausted which is replaced by HEPA-filtered fresh air.

Newer Disinfectants• Persistent antimicrobial-drug coating that can be

applied to inanimate and animate objects containing silver (Surfacine)

• A high-level disinfectant with reduced exposure time (ortho-phthalaldehyde)

• An antimicrobial drug that can be applied to animate and inanimate objects (superoxidized water)

• New sterilization methods – a chemical sterilization process for endoscopes that integrates cleaning (Endoclens)

Newer Disinfectants

• Solutions of chlorine dioxide are also commercially available as liquid sterilants—under trade names such as Tristel and Medicide

• Gaseous chlorine dioxide system is currently being used in several medical applications, including the sterilization of contact lenses and the secondary sterilization of overwrapped foil suture packages

Recent Research

• Psoralens and UVA (PUVA) An interesting example of the

development of sterilization techniques for specific applications is the recently reported use of ultraviolet light in combination with psoralens to purge blood plasma and platelets of pathogenic organisms.

Recent Research

• Ozone - Its use as a sterilant, however, has been limited because of its instability, which precludes storing it ready for use, and because of the difficulty of generating pure ozone. The Cyclops Co. has introduced a machine for sterilizing endoscopes that pumps humidified ozone through the unit.

Recent Research

Recent Research

Recent Research

THANK YOU

“Sunlight Is the Best Disinfectant”

Date post:	16-Apr-2017
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Recent advances in sterilization

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