HYGIENE

INTROAucTiON
Hygiene is the science of personal good
and mental condition.,
This is a state of disease
disease) or infection.
health and astate of sound,
free condition. (a
physical
situation non - conductive to
Topics

Hygienic measures
Sterilisation
Disinfection
1.
Measures
Micro - organisms:- Bacteria , Spores,
(Bacteriology) algae. They can also be Viruses, Protozoa, Fungi
medical term is Microbes, pathogens arecalled germs pathogens but the basic
disease causing microbes.
Diseases and their infectious ways. (Clinical
Aspects)
2
Sterilisation
This is the process of killing all
pathogens ie to maintain a Aseptic state.
3
Di_infection:
Process of killing Most pathogens:- Boiling (100 c) for less than 4
hours.
BACTERIALOGY &MICROBIOLOGY

This is the study of micro organisms invisible with naked eyes.

They reproduce bybinary fussion. This properly makes them most
because their rate of fission is extremely &alarmingly high. dangerous
They feed on chemical material from the sorroundings. Energy for
function is obtained from light or chemicals. these
The Bacteria can only digest Extracellulary ie. outside the cell.
It exeretes digestive enzymes which digest the food material which
intern
diffuses into the cell through the wall by 0SMATIC pressure drop
by the bacteria is then broken down for energy and waste material produced
The Excrete is most dangerous became it normally affects the host execreted.
(very
dangerous chemicals)
1. Seretion of enzymes 2. Dyestion (Extracelular) 3.
4. Metabonsm 5. Exeretion.
Absorption
 NECESSITY OF HYGIENE IN HOSPITAL INFECTION : This is an
HOSPITAL infection acquired by a patient during a stay in
hospital. This can be :
Germs are every where in the air. soil, water,
clothes, dust and in our bodies. It should be a) Self-infection : infection may occur
noted however that most of the bacteria are because a patient is weak and has low
harmless and play very important roles in our resistance or patient may be infected by
lhfe e.g. they help in break down of food into pathogens in his body when they reach
useful substances, help fight against new site like open wounds.
pathogens, useful in food production (bread,
cheese, wine, butter).
b) Cross-infection - this may be direct
Now that the germs are invisible in our naked
from person to person or more usually it
is indirect by way of equiprment,
eyes, we are therefore not able to differentiate around, medicaments, solutions or foed
the useful ones from the pathogens and we or hospital facilities. The control of
must therefore exclude or control microbes in
microbesin hospital environment will
certain situations. play a part in the control of cross
infection.

i) Critical sites certain places inside

human body and all open wounds are Hospital staff are normally in good
very weak and vulnerable to infection health but should realise however, that
and microbes should never be allowed in in spite of their own good health they
such sites.
may carry resident or transient germs
(microbes picked up by contact with
infected material) which are capable of
iü) Laboratories - microbiolo gists must
work with microbe free materials
causing infection in a patient whose
resistance is low.
because stray germs will confuse their
results. People b t ot Pexy
Colonise
Transient microbes on the hands will
usually be removed by washing and most
iü) Special work outside laboratories of resident germs will be cleared by
Harms microbes may interfere with washing. Therefore hand washing with
Harnful brewing, antibiotic manufacture. plain water and soap will control
hospital cross infection considerably if
the patients and medical staff co-operate
iv) The hospital environment it is
impossible to exclude all microbes from Iwashing hands:
hospital environment but all pathogens
must not be allowed anywhere in the (See hand out)
week and vulnerable human (patient).
 Loconofp
Structulr
hair.(ile
Aiicroscopic
MOVEMENT ,
Most are unable to move and are carried passively along the
media they live
Others bave flagclla which aid in moving
Others are spiral shaped eg Psendomonas, vibrios ctc. && flexiblc and can
vibrate (wavily) and move, (rotate).
REPRODUCTION
They reproduce assexualy by binary fission mostly once even 20 minutes.

DISEASES CAUSED BY HOSPITAL/OUTSIDE INFECTION

Plague pasteurella pestis
whooping bordetella pertussis
Pnenmonia streptococcus Pneumoniae
Lepsosy mycobacterium leprae
Syphilis treponema pallidum virus
Gonorrhoea neisseria gonorrhaeae
Tuberculosis mycobacterium tubelosis
Diptheria corynebacterium diphtheria
Typhoid salmoviella typhi
Dysentery shigella sonnei
Cholera vibrio cholerae
Scarlet fever streptococcus pyogenes
INVASION MECHANISMS

They protect themselves by forming copsules.

Secret enzymes which breakdown &clear ways for them.
Produce toxins,.
() leucodidins kill lenkocytes
(i) Extoxins - produced / secreted outside the cell / very dangerous eg.
clostridiun tetani.
(iü) Endotoxins - produced inside the cell which is dischansed after it dies.

Others produce antibiotics which kill other bacteria eg. penicillin,

streptomycin, tetracycline, chloramphenica.
EFFECTS OF VIRUSES ON HOST CELLS

Celldegeneration
cell fusion - malignant syncytia
cell proliferation -tumour producina
lysis - destroy cells
latent infections - no visible signs.
inclusion bodies - iregular new structus found in invaded cells.
Hospital staff are normally in good health but should realise
ther own good health they may carry resident or however, that in spite of
contact with infected material) which are capable transient
of
germs (microbes picked up by
causing
resistance is low. infection in a patient whose

Transient microbes on the hands will usually be removed by washing and

resident germs will be cleared by washing. Therefore band washing with plain water most of
soap will control hospital cross infection considerably if the patients and medical staff and
co
operate in washing hands:

(See hand out)

 MICROBIOLOGY
Microbiology
The majority
is the
are
study of
micro-organisns including
even death. harmless, many are beneficial but a bacteria, viruses and fungi.
few can cause
Approximately
form of infection 5% of all patients disease and
during their stay and a similaradnitted toof hospital acquire some
with infections. The number patients are admitted
urinary tract, surgicalmajority of
hospital-acquired
and the respiratory infections are those of the
surprising in view of thewounds tract. This
compromised state of the patient. Many ishaveprobably not
anaesthesia, Invasive procedures, such as undergone
receiving immuno-suppressive drugs. Infectlon catherisation
is a
and surgery, or are
result in pain or even death. It is likely to hazard to any patient and nay
in hospital and length of time off considerably increase the length of stay
(e.g. antibiotics, repeated dressingwork. Infected patients require expensive therapY
special isolation facilities. change), careful barrier nursing and occasionally
Bacteria
These are minute unicellular organisms varying in
0.001mm). Each bacterial size from 0.3um-14pm (lpm=
cell is an independent living unit
from the surrounding material. Many are
essential to life,
deriving its nutrients
synthesise vitamins essential to human well being, thosee.g. in the bowel, which
and/or provide plant nutrients and those which responsible for decay
are of many different shapes. and are convert curd to cheese. Bacteria
able to withstand widely different
circumnstances. They can be examined using the high power lens of a
microscope and can readily be grown in artificial liquid or solid light
media. Like all living things, bacteria require food and (argar) culture
warmth and the water and in some instances
correct atmospheric conditions to flourish.
(Examples of bacterial shapes and forms and those causing hospital
found on the acco mpanying sheet.) in[ection can be
Viruses

Viruses may also be responsible for hospital-acquired infection, such as

measles,
nunps, coMinon cold, influenza. They are different from bacteria in several
they are too small to detect with a light microscope (i.e. 1/10 - 1/100 size ways;
bacteria) and have to be studied with a powerful electron of
microscope. They are
entirely dependent upon living susceptible cells and therefore cannot be grown on
artificial media but have to be grown in animal cells or those adapted to cell
culture.

Fungi (including yeasts)

These are longer than bacteria and tend to form long thread like structures
(filaments). they are more complex than bacteria and are only occasionally
responsible for hospital-acquired infections (e.g. oral thrush in babies).

INFECTION
Infection results when micro-organisms capable of causing disease have gained
access to the tissues, established themselves, multiplied and caused some adverse
effect upon the host. For infection to occur or be transmitted to a new host the
following sequence is required:
1. Apathogen (i.e. organism capable of disease).
2. A method of entry into the host.
3. Establishment and multiplication in/on the host.
4. An exit route and means of transmission to a new host.
16/1
 ROUTES OF ENTRY
Inhalation via mouth or nose, e.g. TB, diphtheria, influenza,
common cold,
mumps.

Ingestion via mouth to alimentary tract - food, water, faeces, e.g. dysentry,
poliomyelitis, salmonella.
Inoculation through skin and mucus membranes, e.g. surgery, insect bites,
injections, etc.
Placenta transmitted across placenta, e.g. rubella, cytomegalovirus.

ROUTES OF TRANSMISSION

Contact

Direct personal/sexual contact.

Indirect - via instruments, equipment or clothing.
Airborne Droplet nuclel from respiratory tract. Bacteria dispersed from
skin, dust containing animal excreta, soil, etc.

TYPES OF INFECTION

Endogenous self-infection, causative organism comes from another part of the

victims body.
- cross-infection, organisms causing infection acquired from outside
Exogenus
the victims body.

Nosocomial - hospital-acquired infection.

Opportunistic - organisms of low pathogenicity which cause infections in

immunologically compromised patients.
Nornal flora (commensals)
The skin and mucus membranes harbour or support a wide variety of organisms
without causing infection. Many of these are essential to life.

STAFF HEALTH

Bacteria causing infections are usually Eacherichia coli, Klebsiella, Proteus,

Pseudomonas, Bacteriodes and Staphylococous aureus. These infections are unlikely
as TB, typhoid fever
to be harmful to staff. Serious communicable infections, such transmitted
hepatitis, may occur in hospital but these are rarely to other
and
patients and staff. Transmission is prevented by good personal hygiene, particularly
handwashing and immunization when indicated. The Infection Control Nurse and
Occupational Health Department will advise where necessary.

L..y

16/2
 PREVENTION OF INFECTION

Airborne - Ventilation (theatres, ITU, infectious diseases).

- Isolation (source and protective).
Face masks.
- Protective clothing to reduce dispersal.
Disinfection of respiratory equipment.
Suitably designed cleaning equipment, eg. vacuum cleaner
{iltered exhaust.
Prevent dispersal of dust (danp-dusting, use. of dusSt -attractant
mops).
- Prevent aerosols from cleaning equipment and humidifiers.
Contact - Handwashing and disinfection.
Protective clothing.
Careful preparation of food, refrigeration, cooking.
- Disinfection/sterilization of instruments.
Adequate decontam ination of equipment.
- Environmental cleaning and disinfection.
- Exclusion of vermin.

Environmental sampling - Use to:

1. Identify routes of spread of infection.
2. Identify staphy lococcal dispersers.
3.Evaulate cleaning or disinfection techniques.
4. Research and teaching purposes.
BACTERIA WILL NOT THRIVE ON DRY CLEAN SURFACES

Bacterial growth curve

BACTERIAL GROWTH CURVE

Log
Count

5
10 16 20

TIme (hours)

a -b log phase
b -c logarithmic phase
c-d stationary phase
d - e decline phase

16/3
Disinfectant failure
Inaccurate mneasurement
Instability during storage
Refilling dirty containers
Topping up
Presence of inactivating material
Inappropriate choice

Application of disinfectant policy

I. Enguiry - purpose of disinfection
2. Alternatives - heat or disposables
3. Selection of suitable disinfectant or alternative
4. Distribution

5. Instruction on use and distribution

6. Check and renew policy

Disinfectant selection
I,. Nature of formulation i.e. Environment (spillage), instruments, skin
2. Range of activity:- Spores, vegetative bacteria, viruses, fungi
3. Recommended "in use" concentration
4. Cost

5. Toxicity

6. Corrosiveness, damaging effects during use

7. Stability

8. Inactivation by organic matter, hard water, detergents etc

9. Rate of kill

10. Smell/taint
 3
HEALTH AUTHORITY

Cleaning
Cleaning with so ap or detergent will remove most mlcro-organisns frorm a surface.
Afurther reduction in numbers occurs as the surface dries. Thorough cleaning and
drying will be adequate treatment for most surfaces and furniture in the hospital
environment. Cleaning before disinfection of equipment nay also be required to
obtain adequate disinfection.
Disinfection

Disinfection by either heat or chemicals will destroy non-sporing organisms,

reducing them to a safe level. The term disinfectant is used here to include
antiseptics which are applied to wounds or the skin. Chemical disinfection should
only be used if heat treatment is impractical or undesirable, e.g. for skin,
endoscopes, and only on surfaces known to be, or particularly likely to be, heavily
contaminated with non-spor ing pathogens. This process may also be used for any
object likely to come into close contact with a susceptible patient, e.g. treating a
cubicle occupied by an infected or immunosuppressed patient, or for respiratory
equipment.
Sterilization

Sterilization means the complete destruction of all forms of microbial life,

including spores. Equipment and materials used in procedures involving a break in
the skin or mucous membranes should be sterilized, e.g. surgical instruments, skin
disiníectants,
cavities.
and products intended for parenteral use or for instállation into body

Autoclaving with stean at1nosplherlc prcssure (115°-134° C), or dry hcat (160°C [or
1 hour) are acceptable methods for hospital use. Chemicals with sporicidal
properties (glutaraldehyde, e.g. 'Cidex') nay sterilize under favourable conditions,
but are less reliable and should not be used if aviodable. Alternative methods may
have to be used fot heat-sensitive equipment, e.g low temperature steam, ethy lene
Oxide.

Disinfectants and antiseptics in current use

The following are avialable as part of District policy (see Tables 1 and 2). Other
products may be made available to individual users if there is a specific need and it
can be shown that the product is effective. Departments requiring additional
products should discuss any special requirements with the pharmacy or infection
control department.
The use of chemical disinfectants

Microbes are normally present in the environment of the home and hospital, but
most areharmless and only a small proportion cause infections in susceptible
people. They can be removed by thorough cleaning with a detergent solution.
Because microbes die rapidly on clean, dry surfaces, there is little advantage in the
routine use of chemical disinfectants which can seletively kill harmless microbes
and allow those most likely to cause problems to flourish without opposition.
Freshly voided urine in normal people should be free from organisms. Ålthough
faeces contain many millions of organisms, large numbers of similar organisms are
also present in dish cloths, face flannels, mops, etc, It is for this reason, that we
try to restrict the use of disinfectants to cleaning up spillage we know is likely to
be contaminated with the microbes that cause specific infections, e.g. typhoid,
food-poisoning, hepatitis, etc.
Indications for use

1. Faeces or vomit A clear soluable phenolic disinfectant, e.g. Clearsol, should be

used to clean up faeces or vomit from a patient with
diarrhoea, enteric infection,or in other situations where risk of
transfer of infection is considered high.
2. Sputum A disinfectant should be used ior cleaning sputum spillage
from patients with diagnosed or suspected pulmonary
tuberculosis or with known methicillin-resistant
Staphylococcus aureus chest infection. A clear soluable
phenolic disinfectant, e.g. Clearsol, carefully diluted to the
recommended concentration, should be used.
3. Hypochlorite solution or powder should be used if there is spillage of
bloodstained material from any patient with a known or suspected hepatitis B
virus or HIV infection, or from a jaundiced patient in whom the diagnosis is not
known. For dilution, see Table 1.
4. Urine Disinfectant is not required except where there is a urinary
tract infection with a particularly virulent or transnissible
strain.

Disinfectants may also be required in other situations. These will be recommended

by the infectioF control staff where there is specific risk.
Methods for the cleaning and decontamination of equipment and the environment.
Method for general cleaning of spillage from surfaces
1. Always use freshly prepared solutions in clean containers and discard after use.

2. Dilute general purpose detergent, e-g. "Hospec', by adding approximately 5ml to

a standard polypropy lene bowl filled with hand hot water. Never use a sink.

3. Add up to six disposable wipes e.g. paper towels.

4. Wring out and use one wipe.

5. Discard the wipe without returning it to the bowl.

6. Continue until cleaning is complete, or all wipes are used.

7. Prepare a fresh detergent solution, if necessary.

8. Dry thoroughly with paper towels.
16/6
 secretions/excretiorns
Method for cleaning spillage of contaminated
of contam inated waste nr ete
1 Cloves should always be worn tor handling
disinfectants.

disposable materials, e.g. towels, gloves, used for renoving contarminated

incineration.
2. All should be discarded into a yellow plastic bag for
spillage
fluids .
spillage of large volumes of urine and other contarninated
1 For
spillage with paper towels so that all liquid is absorbed:
(a) cover towels.
disinfectant solution using fresh paper
(b) wipe over with appropriate
of blood or small amount of other body fluids -
4, For spillage
non-abrasive hypochlorite powder, e.g. "Diversey'. 'Titan', etc,
(a) sprinkle with absorbed, then discard using paper towels.
until all fluid is
surface with detergent solution using fresh paper towels.
(6) wipe over
 The elimination or
Disinfection:
bacterial destruction
spores, and is generally applied to theof process of making but
micro-organisms,
not free
objects the
frominfection and safe to handle. It is not an absolute term and may be applied
selectively.

Typesofdisintectants:
Advantages Disadvantages
Gluteraldehvde broad spectrum expensive
Cidex','Totacide!, (inc.TB,spores,viruses) relatively unstable
non-corrosive toxic
'Aseo)
instrumentdisinfectant not readily inactivated Occasional allergic
rapid in action response

rapid in action poor penetration

Alcohol can only be used on
Instruments leaves surfaces dry
cheap clean surfaces
Clean surfaces flammable
non-toxic
Skin non-corrosive
non-irritant

unstable
Hypochlorites broad spectrum corrosive
('Sterite,'Chloros', (inc.TB,spores, viruses)
inactivated by
"Kirbychlor',etc.) rapid in action organic material
Discard jars cheap
non-toxic at low concen
Spillage
Environment tration
not readily inactivated by
man-made materials

Clear soluable plhenolics broad spec trun (inc.TI) toxic

unpleasant smell
('"Hycolin'
Stericol,Clearsol" often contain campatible and taint
Discard jars detergent
not readily inactivated by
Spillage organic material
Environment cheap

Providone-iodine
("Betadine Disadine'etc.) non irritant/toxic disinfectants for use on thne
tend to be
Chlorhexidine h l lhey are non-sporicidal and
(Hibiscrub, "Hibitane'etc.) Inore effective against Gram +ve cocci. They
Skin disinfectants are expensive and should not be used for the
environment
5) 4) ) 2) 1) (5Al) gae
Protozoa 4) 3)
VirusesBacter1a
2) 1)
Group Table
Fungt
Dis Table :
manig, Lasa Boil ea
imouids 1.3 higher
chiracteristics. The used SIZe
tormiiable
a suesCausefarely tine inandunicellular.
Microorganisms
the
except range resistance agents. bilityledge
The
exclude
procedures
Hygiene:
MICROBIAL
TheTARGETTHE
ses and
Tvpes naior to and that
disease
and indoor
of of rational
fever, wonds yeasts ot
lorms
preventprim1tive are
harmtul nnouth.
parts
the
primitive
ot
term
survival theirharmiul
(exani mI.ro9rganisms groups need to
of challengenormally environments,'microorganism' but that
selection
if in upper physical nature
s0ma Colds, fod ples) plants
Green
Animals plants,notbutSubcellular
photosvnthetic Someparticles NeitherAtfiliates
together
life.
and
control
or
nature,
thevthese of
the
are of they
a life microorganisms in are
are gain respiratorymicroscope widely have different intended
some sterile. urogenital and and
paisonin5; resemblance to listed with to situations forms;
Hepat plants microorganisms
of
the
the access
distributed on little
and
distribution, correct Types
inTabletheir spread the conditions
nor
themethods Despite most chemical
embraces to
ts A+
animals
relationship
tobuttract.tract,
human toelse
requires kill,
epins B,
distinguishing
ot organs observe performance
intection.
that
their
likely
are large
Thev skin
in in
common them
of
and their remove
of
Herp, Tefans oDparasttic intraceflular
paras1tes
Free-livingFree-living
Free-living p3rasiicObligate
or Free-iving
parasitic or
Growth
hab1ts
present
small or intes
outdoor
them. wide
biocidal
a
their capa
know Micro
are tis toare and
kness to are
or
of:
organism
), funa, n Diate
mydium
hoeq
h Se. b.iCternal
rut Human.
De
oaules (uns resh plants 0, i
uICes.avng Jnimats,
witer,
animal.
water. oganichosts
plants,
tups, aloscess sol
organtc

plant
matter.
an1malb.
mater1als.
or

Polioy soil.
 Pvessbre amd Pressue Equyaces

which corresponds to 29.92

Ihe standard atmospheric pressure is 76 c1n Hg,mercury (mm Hg) is called a
Hg, or about 14.7 lb/in. A pressure of l mm of
invented the barometer in J643.
T in honor of Evangelista Torricelli, who
pressure in terms of pressure as a
Aunit such as cm Hg is not a valid unit of
quite useful. The SI unitof pressure
orce per unit area even though such units are
the pascal (Pa), a pressure of1N/m², a rather small pressure. In meteorology.
.s unit equivalent to 10 Pa
pressure
thebar (or millibar, mbar) is a commonly used to
is also frequently encountered and is equal
or 10° dyn/cm". A kilopascal (kPa) equivalents that may be used to convert trom
10 mbar. Table 11-2gives several
one pressure unit to another.,
TABLE 11-2 PRESSURE EQUIVALENTS
dyncm?
1N/m? = | Pa = 1.450 × 10-4 1b/in = 10
.501 × 10- mm Hg
1Pa = 10- bar = 9.869 X 10-6 atm =
=750.0 mm Hg
1bar = 10 Pa = 14.50 lb/in' = 0.9869 atm
1mbar = 10-3 bar = 0.750 mm Hg
1lb/in = 6895 N/m² S1.71 mm Hg = 27.68 in. H,O
=6.89S kPa = 68.96 mbar
76 cm Hg = 760 mm Hg
1atm = 1.01325 × 10 N/m' = 101.3 kPa =
Jb/in 34 ft H,0
= 760 torr = 1.013 bar = 14.7
mm Hg = 249.1 Pa = 2.491 mbar
1in. H,0 = 0.03613 lb/in' = 1.868
1torr = ]mm Hg
pressure because of its constancy
We are usually oblivious to atmospheric deternined is called the absolute
pressure P just
and uniformity. Therefore, the
presSSUre. The absolute pressure is the
pressure to distinguish it fromn the galge hand.
per unit area exerted on the interior walls of the tank. On the other
force ever-present,
tank above and beyond the
gauge pressure is the pressure in the pressure and absolute pressure
essentially constant atmospheric pressure. Gauge
are related as follows:
Pg:
gauge = Pabs Patm (11-11)
Pabs = Pgauge + Patm
industrial applications are calibrat
Almost all pressure-indicating devices used in
ed to read gauge presSsure.
 rietschoten
&. hoUWens
sluisjesdijk 155
tel. 010 - 29 88 11

clektrotechnischa maatschappij b.v.

Jx415Y+0 +EAARTH

1.2.14
CONTROLLING
CURRENT
220V
MS, 10-- o---11
12

240V-50 s
TF
220V-50 VA

S.6.7.0,

cONTROLLING
CURRENT 12 12

SWITCH 80X PARTS CODE

MS MAIN SWiTCH
C CONTACTOR
HEATING ELEMENT
FUSE
L1 L2 *: FS FLOAT SWITCH
P red greeny
;L1 LOW WATER SIGNAL
PS PRESSURE GAUGE
MS L2 IN OPERATION SIGNAL
SW
YF TRANSFORMER
SW SWITCH
B BUZZER

i.AUTOCLAVE TYPE: TD487G *WIRING DIAGRAM

WITH HEATING ELEMENT PROTECTOR
 A ERILiSATION AND I5INFECi!0N 105
ol sterility is
perlormed have such
Uccasionally in operating thcatrcs.ulra-violet screens. lhey are also used
schoolrooms see whether the air canExpcrients
have been done in
CHA PTER 9 to be kept relatively microbe -free by
this means. In these cxperiments ultra-violet lamps were
STERILISATION AND DISINFECTION hung from the
ceiling to sterilise the upper layers of the air. It was found that school
!
children using these classrooms had a lower rate of respiratory disease than
Many terms are rather loosely used in discussing children using untreatcd classrooms in the same school. presumably
are a few working definitions (see also Glossary,sterilisation.
page 163).
What follows because the numbers of microbes were reduced in the air of the treated
Sterilisation means the destruction of all living microbes, and inci rOoms..,*
dentally of all other living matter. It must, of course, be remembered that excessive exposure to ultra-violet
Disinfection means the destruction of all vegetative microbes, that is to light is very dangerous to human beings. When objects are being sterilised
say, excluding spores. by ultra-violet light, exposure of the human body, especially the eyes, to
A bacteriostatic agent is one which prevents the rays must be avoided, by protective clothing. by wearing goggles. and
but does not necessarilv kill hem
microbcs from multiplying, SO On.

Germicide means the same as disintectant Another disadvantage of ultra-violet irradiation or sunlight as a disin
An antiseptic is a substance which is applied locally to prevent infection, fectant is that to be effective it must act directly: on the object to be
sterilised, Dirt may prevent ultra-violet rays from reaching the object to be
either by killing microbes, or by preventing them from multiplying. sterilised:The rays will not penetrate ordinary glass.
Methods of sterilisation fall into two groups: (a) Physical and (b)
Chemical.
2Heat

(a) Physical Methods of Disinfection The physical means of sterilisation which is used more than any other is the
application.oof heat. This can be applied in any number of ways, of which
1. Sunlight and ultra-violet light. thefollowing are. the most important:
2. Heat.
(i)) Hot water sterilisers
(ii) Hot air ovens (i)*Hot Water Sterilisers
(iiü) Infra red heating çasiest way of applying heat is by heating water in a kettle or a
(iv) Microwave ovens hot-water _teriliser. Such sterilisers used to be a feature of all hospital
(v) Steam methods - autoclaves and pressure cookers
wardsaFd.operating theatres, but they are now obsolete. The highest
temperature obtainable in an open vessel is 100°C. At this temperatüre,
3. Irradiation. the waterevaporates and turns to steam. Until all the water has
evaporated,"the.temperature will remain steady at 100°C. On escaping
I. Sunlight fromthevessel, the steam immediately condenses back into water,
all living things. producing clouds-of droplets which heat and dampen the atmosphere,
Direct exposure to the rays of the sun will eventually kill For example,the.. often: makingit; verydiflicult to work, and incidentally, spreading infection.
Sunlight as a disinfectant can have appreciable effects.
play of sunlight on the surface of an open-air swimming pool does kil some
bacteria and signifies that, other things being equal, open-air poolsare Effeçiyeness
the washing
likely to contain less microbes than enclosed pools. Hanging
obvious advantage of How effectivesis hot water as a sterilising agent? All viruses and all
seconds by
out in the sun sterilises it as well as drying it. The that it costs nothing. vegetativegthatis,non-sporing, bacteria are killed in a fewenough to kill
sterilising by sunlight, where and when available, is lethal effect, and the temperatures:well below that of boiling water. 60°C is hot
exert the
It is the ultra-violet rays of the sun which of an ultra-violet lamp. Such 80° C. Spores, however, are
mostrof themthough some can survive do
same effect can be achieved artificially by
use
or higher temperatures to kill them than
another.materAIlspores need
a lamp is often used to sterilise
boules of biological fluids, such as blood vegetative bacteria.Some can resist boiling for several hours, though this is
have
conveniently sterilised in any other way. thes, to be quite sure that microbes of all kinds
plasma, which cannot be formn of a scre,to sterilise air exceptional None. hours.
Ulra-violet rays can also be used in the degree beenki;; boiling should continue for six
entering aroom. Many laboratories in wlhich work requkg a high
104 \
 operations spore-bearers.
necessary
mehod
but clave. adequate, isonewhen
vegetative 106
cro-Wave Ovens(iv) infra-red
often
insulated however,
anywhere oven time cotton-wool,
syringes
and fabricssporing as timerangeHot-Air Ovens(ii)
However. not
advantageshortmore Infra-Red from Heating
light (iüi) This The is This
In The Another steam. not
needed of 'scalding one
this, for cool severely
of The really
used sterilising can but is,
infra-red forty-five in organisms
and conventional
temperatures. of than is
suitable about
lamp bemuch which
by
down and the is organisms,
to however, only of
eating for space is disadvantagemetal will inadequate practice sterilise all
sterilisation.
thatattained general limits and to
a kill spore-bearers,
boiling
surgical out'course,
sterilising is two again, trying
such time sourceheat. end means temperature
eventually
a the minutes. and other are MICROBIOLOGY a
to convenient hours the spores. gas should of as
baby's
as which These practitioners of killed instruments which the quite
to
the heating is that often glass
fabrics The instrum1cits
an such the use or boiling
and kill
a is
esired syringes big hasspectrum
in
this containers,Soasthe damage Theelectric danger feeding
impracticable,
In
oven. ascan of higher
in unsafe. be cause
vegetative
the
all. the hot which
way does a kindMost long long cannot, the forty-five used;
advantage to be usual instruments
erat7 in of A lamp. and objects as method, enough during circumst
moving
a
not directed of time
the
hot-air
are It and bowel tobottle IN
using held consists homes ortherefore, rubber
temperature for PATIENT
syringe have sterilising
private and temperature, will thmicrobes,
e
A longertotaken minutes. potentially clothing
only to examnple, in
this
conveyor
to
of high on be glass which, oven dispose an
infections, babyances the and
of have and kill for
unit.form infra-red be for nurses. sterilisedthan for
operating CARE
takes temperature to
rays home.
can or spores
be Hot can a must comes of indeed as
done aboutobjects an plastics.
of
belt most
however, is dangerous offew a the may
which be sterilised
a oven the metal air l60 the be vegctativerapidly be
matter sterilisation, passingheating. in ten performed have will minutes list, rather mostlyhome
This
be it
to actualovens is°C, lessused sterilised.
a in
apparatus. Linen, not
confined minutes;sterilise ,of give damage 'scalding the is
the to is in inthe over acting some unnecessary
of sterilising to
as in than
under
l80 no
kitchen, beheat
useful this
effective which
exposure organisms from it case
onds Another, almost cotton, a surgery.betwcen may
and °C visible in
this them most wide autoother If from when
and the up for way. it the beout
is an or all is

B
displaçement
the willcondenseonthe
*These:are . Qutthe
SHighdisplacemcnta4toclaves, dive to heavie
largelyachivedby! thautoclave
e the
plete;temperaturciis. ture keeping.the-steam areto. clavsteam kill-all
erIn.the theben.sterillsed
microbesnto Gxhaustpipeforair
bycomngnat
utoclava Steriliseda sufficient
commonest -Autocaves
autoclave Steam How steam Autoclave(v) Oven some
The be. only.
ng Athscndothe VIerhan effctivencss-of The,
steam:nust
steamito claveyetThËs IEmoyalkof is, sealed The
YGOUnstam,
firststepP:in, be:used.correctly an is is an undermost getsHowever,
parts
cuumautoclaves. and'remain fed iving
autoclave a
themain to addition
9 sterilising, effective mi_take can off into more over
enter at:thesteam} sterilise important of
older:type are be objects pressure,
hejautoclave be not; from this th e
complicated maintained an
effective the
the sterilising the the thepure,
gins. reasons air top. at so sterilising on is autoclave
the
at works
in difliculty. object
of
STERILISATION
DISINFECTION
temperature
AND
ilising sterilised a use inthe it
of betore the if air. steam its to a methodin
a
types, must The powerful the the contact
not is think itoutside, fifteen turntable
aut bottom, own. is steriliser an nay
The why take and process, steam of
In mixed steam not presure
the entering the as
necessary Autoclave.
and air modern agent at from
ing
igh-vacuum contaminateobjects,
be hot This that pieces of be
hamber, ve much filtered,
temperature is exhaust autoclave a with
must the the minutes. of
on th e is sterilising with enough. greaterthan sterilising ellecively or
may
it forced
the fed in isthe desired of
a than micro-wave
the steam steam not temperature
to boiler, ol
and air 'high-vacuum' air. for temperature
actually the apparatus
time and take whole less in understand This hot inlra-red
or must out fromitself pump. mnust, the time
so.
drive
machines time the they
at can agent. Any It Only level and air, used sterilised,
-an-hour it falls. of temperature
they objects may required follows
c. out bethdrive
e drives the therefore,mixture reach allowed; indefinitely. atmospheric and in ovens
to Otherwise will
admitted In steam inside (see ofthe hospitals
heating
all aresterilise are bottom top how the steamn
bringcome
which
out autoclaves, outolder the that Fig. interior other is
the
replacingmore and time.
with at steam uneven,
or pathogenic
the the
object hot this the they 29) to
air, out once by there be for is at is parts
a
more th e 'downward
air air. air autoclave pressure. of
reliable. than have gravity. tMoreover.
he tempera air work. and inside attained 120
the
bymicro-wave
before of simply effective and
steam again isAir this reduces to at
means may
for the do just the com if auto °C
The they
an
is is be this the will while
is If by of not 107
 29.g.

plificd
33
CYLNDER
DOOR 33 19 13

() VALVE
AUTO
DRAIN CW
CONDENSATE
SALLFEED VALVE
TANK EXHAUST
CONDENSER CONNTH CONDENSATE
TEST CONNEC
REG NON-RETURN TIONSTEAM
VALVE VALVE
MAIN LiNE
LINESTRAINER VALVE STEAM
AIRGAUGE
SAFETY
VALVE
iagran
24
21 CwNNECTION FLOATVAtCPROCEePTE
VALVE TORCONNECTONI GAUCEGVALVE PRESSURE
CHAM8ER
CHAMBERORE
FILTER JACKECKET
GAUGS HAMBSR
25) ESTEAM
TRAP STE PRESE TO
DESCRIPTION
26 AM
VAVE SYPIHON
SURE OCKCHAMBER
GAUGE &
MP
TRAP
of TION TOR
an AUGE

us s.
oclave. VALVE

A 18
least

it
shows

iow
|30
licated
+31 15

this

..
best;
the and:screw:çapped
1.day.This
Testingautoclaves
efphilic
apdres The suchas}hottair
wha So It
cas penetratethem.
autoclaves, of
Howeverthey
by:thesteam
It cooker
therefore
that. ordinary: dressings,
will:
isglassÇòntainers
Assembled
way more in
whether loadsmade quickly.
mechanically 136° through. Thishour, and 1s
A The
efficiency donotire¡lise isothèr
unsafethere not
What the of
small In (weinty
surprising pressurecycles
is driving th¡nmuch C, mneans a the
ng can
methods to penetrate autoclave cancondenses
contents a machines,
whole
he
high-vacuum is
The temperature
more.
or
is
when linen
convenient in used minutes.
easily of use asyringes
danger be cansterilisingsmaller,
cycle a that
in under
must sterilised cooker sterilising
at
off displacement than
autoclaves how ehanan a the The and be the in A
be bottles
that syringe into cycle. with emerge
OS done oftenoven,
the autoclaves
plunger of cannot contents pressure,
wrapped cotton
be
way
on
steam
the got
isabout
chamber
to in
a
end. in workingNTERILISATION
and autoclave a
norImala
After AND
DISINFECTION
allowed
infecting the the the high-vacuum
through a time
placed which Other in small displacement sterilising,
by process one or interior. be caps damp. thatThis sterilising
should an of
sterilised
thirtymachine, is
various irradiation. has ofautoclave?
objects, sterilising at day to
short the
sees has sterilised methods loosely, and steam in meansit
in have the been impermeable screwed When the is is of comc
be is
polythene been which the
minutes full asair cightcyclc the
autoclaves syringe end economical
ns. regularly ineffective.
methods, Syringes
toremoved and
object
steriliser. autoclave
course or machine.
in that a is down.
assembled in in small this which higher
pumped hours, nay steam
be autoclaves havedown, such Anything of nearly
used when many is does asthe in the
of packs, packs
to notobjects. th e ofthe
temperature,
sterilising thus Thismust
whichtested
for from can be are
a sterilising 1n varies a empty.
the to The only
for it way harmed not day.
it,largest out
sterilising, sterilised. after is only used such types which cooker
being cycle
sterilise take may be
assembled however, steam of four
set preferablythe
- sterilising
assembled the either, not that matter, from
takeschamber
almost take
the cycles driven
barrel. be for
sterilised as of can
the by process.
cools types.
following polythene, much usually is
machine another
sterilised these. as instruments.
steam. be a there few a just pumped out
by
syringes, syringes, the steam down, can (wo
for reached pressure minutes So
every people Insteam in Steam smaller as can hours.
be by
use. this ismany long
about half
can are an can out very got air. i09
in or All so no be

be