2. OBJECTIVES
• Epidemiology.
• Definitions.
• Criteria for defining surgical site infections.
• Wound classification.
• Different scoring systems.
• Pathogenesis.
• Factors that determine surgical site infections.
• Treatment of SSIs.
• CDC recommendations to prevent SSI.
3. EPIDEMIOLOGY
• SSI is MOST COMMON hospital acquired infection in surgical
patients.
• 3rd most common hospital acquired infection.
• Accounting for 38% of nosocomial infections.
• -2/3rd incisional.
• 1/3rd organs/spaces.
• Incidence of SSI ranges from 2 to 5%(for clean surgeries) and 20%
(emergency colon surgeries) of more than 30million patients undergoing
surgical procedures each year.
• Over one-third of postoperative deaths.
4. Definition
• Infections that occurs within 30 days after operative procedure if no
implant is left in the place or within 1 year if there is implant lifted in
the place and the infection Appears to be related to the operative
procedure.
• SSI is a type of HAI.
5. When the Infection occurs
Surgical site infection remains a clinical diagnosis.
• Presenting signs and symptoms depend on the depth of infection,
typically as early as POD 4th to 5th day .
• Exception for this is necrotising SSIs caused by clostridium
perfringens and streptococcus pyogenes which may develop with in 24
hrs of surgery.
• Clinical signs range from local induration to hallmarks of infection.
• In organ /space SSIs symptoms specific to involved organ are usually
predominant.
6. Important Definitions
Colonization
Bacteria present in a wound with no signs or symptoms of SIR.
• Usually less than 105 cfu/mL
Contamination
• Transient exposure of a wound to bacteria.
• Varying concentrations of bacteria possible.
• Time of exposure suggested to be < 6 hours.
• SSI prophylaxis best strategy.
Infection
• Systemic and local signs of inflammation.
• Bacterial counts ≥ 105 cfu/mL.
• Purulent versus nonpurulent.
• Surgical wound infection is SSI ..
7. SIRS
Is the Body response to the infection
SIRS is any two or more of the following:
• Temp>38<36.
• HR >90 b/m.
• RR >20 c/m.
• PaCO2 <32 mmHg or mechanical ventilation.
• WBC > 12,000 or <4,000
or > 10% immature.
Sepsis
SIRS +Infection source .
Severe sepsis
Sepsis + MOD.
8. Type of SSI
• Superficial incisional SSI.
• Deep incisional SSI .
• Organ SSI.
9.
10. Superficial incisional SSI
• Infection occurs within 30 days after surgical procedure
AND
• Involves only skin and subcutaneous tissue of the incision
AND
• Patient has at least 1 of the following:
a. Purulent drainage from the superficial incision
b. Organism isolated from an aseptically-obtained culture of fluid or tissue
c. Superficial incision that is deliberately opened by a surgeon and it’s culture
positive or not cultured and patient has at least one of the following signs or
symptoms:
pain or tenderness, localized swelling, redness, heat.
d. Diagnosis of superficial SSI by surgeon or attending physician
11.
12. Notes
The following are not reported as superficial incisional SSI:
1. Stitch abscess
2. Infection of an episiotomy or newborn circumcision site
3. Infected burn wound.
4. Incisional SSI that extends into the fascial and muscle layers
13. Deep incisional SSI
The infection occurs within 30 days after the operative procedure (or within one year if an implant is
in place)
AND
The infection involves deep soft tissues (e.g., fascial and muscle layers) of the incision.
AND
Patient has at least one of the following:
1. Purulent drainage from the deep incision but not from the organ/space component of the
surgical site.
2. Deep incision that spontaneously dehisces or is deliberately opened by a surgeon when the
patient has at least one of the following signs or symptoms :
fever (>38"C), localized pain, or tenderness, unless the incision is culture negative.
3. An abscess or other evidence of infection involving the deep incision is found on direct
examination, during reoperation, or by histopathologic or radiologic examination.
4. Diagnosis of a deep incisional SSI by a surgeon or attending physician.
14.
15. Organ/Space
• The infection occurs within 30 days after the operative procedure (or within one year if an
implant is in place)
AND
the infection involves any part of the anatomy (e.g., organs or spaces), other than the incision,
opened or manipulated during the operative procedure.
AND
Patient has at least one of the following:
1. Purulent drainage from a drain that is placed through a stab wound into the organ/space.
2. Organisms isolated from an aseptically obtained culture of fluid or tissue in the organ/space.
3. An abscess or other evidence of infection involving the organ/space that is found on direct
examination, during reoperation, or by histopathologic or radiologic examination.
4. Diagnosis of an organ/space SSI by a surgeon or attending physician.
16.
17. • Further classifications:
1. According to the etiology.
a. Primary.
b. Secondary.
2. According to time :
a. Early :- within 30 days.
b. Intermediate:- from 1 to 3 months .
c. Late :- more than 3 months to one year.
18.
19.
20.
21.
22. Source of infection
Surgical site infection Classification of sources of infection
Endogenous:
present in or on the host e.g.
SSSI following contamination of the wound from a perforated
appendix.
Exogenous:
acquired from a source outside the body such as the operating theatre
(inadequate air filtration, poor antisepsis) or the ward (e.g. poor hand-
washing compliance).
The cause of hospital acquired infection (HAI).
23. From Bacteria's point of view..
Gram-positive cocci
• account for half of the infections
• Staphylococcus aureus (most common), coagulase- negative Staphylococcus, and
Enterococcus spp
• S. aureus infections normally occur in the nasal passages, mucous membranes,
and skin of carriers.
Methicillin-resistant S. aureus [MRSA]
consists of two subtypes, hospital-acquired and community- acquired MRSA.
Gram- negative bacilli
In approximately one third of SSI cases.
Escherichia coli, Pseudomonas aeruginosa, and Enterobacter spp. are isolated.
gram-negative bacilli are the predominant spacious located at Gl operations.
31. Intraoperative
Theatre environment:
• Positive pressure relative to surrounding
• Laminar air flow (top to bottom)
• Filter all air
• Temperature 18 to 25degC
• Humidity 40 to 60%
• Keep doors closed as much as possible
• Optimal sterilization of instruments (flash sterilisation only for immediate
use).
• Proper surgical attire.
• Minimize personnel traffic.
33. Intra-operative
• Patient skin preparation.
• Proper drapes (incise-drapes must be iodophor impregnated)
• Strict adherence to asepsis technique
• Maintain homeostasis:
a. temperature,.
b. oxygenation, .
c. blood sugar, .
d. transfuse if necessary.
e. Effective use of diathermy.
• Table tips:
gentle tissue handling, careful dissection, effective hemostasis, no dead space, minimize devitalize tissues and foreign bodies
• Suture choice.
• Judicious(reasonable)use of drains.
• Proper Skin closure.
34. Anti septic agents
Properties:
• Able to significantly reduce microbes on skin
• Broad spectrum
• Fast acting, persistent, safe, non-irritating
Examples:
• Alcohol- ethanol, isopropanol, N-propanol
• lodophors -povidone iodine
• Biguanidine -chlorhexidine gluconate
35. Post operative
1. Incision care
• Sterile dressing for 24 to 48hrs
• Aseptic technique in changing dressing
2. Optimal blood sugar control
3. Surveillance.
40. Treatment
1. EARLY IDENTIFICATION OF ORGANISM
2. SOURCE CONTROL.
• Open wounds to drain
• -Drainage of abscess (open/percutaneous)
• -Debridement
• -Removal of implants.
3. APPROPRIATE USE OF ANTIBIOTICS
43. Sterilization
is making a substance free from all micro organisms both in vegetative and sporing
states.
Spores
• is a reproductive structure that is adapted for dispersal and surviving for extended
periods of time in unfavourable conditions.
• Spores form part of the lifecycles of many bacteria, plants, algae , fungi and some
protozoa.
44. Terms used in sterilization
Disinfection:
• The destruction or removal of all pathogenic organisms
capable of giving rise to infection.
• Disinfection does not affect spore state organisms.
Antisepsis:
• The term is used to indicate the prevention of infection, usually by inhibiting the growth of
bacteria in wounds or tissues.
• This is done by the antiseptics.
• Chemicals or disinfectants which can be safely applied on skin or mucous membrane to
prevent infection by inhibiting the growth of bacteria.
Bactericidal agents / germicides:
Those which able to kill bacteria.
45. Bacteriostatic agents:
• Only prevent multiplication of bacteria, but they remain alive.
Cleaning:
• Important preparatory step before sterilization or disinfection, by removing soil and other dirt.
Decontamination:
• The process to make an article or area free of contaminants, including microbial, chemical,
radioactive and other hazards.
46. METHODS/AGENTS OF STERILIZATION
Classification of Sterilization:
1. Physical method.
2. Chemical method .
Physical method:
a. Sunlight.
b. Drying.
c. Heat.
1. Dry heat: flaming, incineration, hot air .
2. Moist heat: pasteurization, boiling, steam under pressure.
d. Filtration: candles, asbestos pads, membranes.
e. Radiation.
f. Ultrasonic and sonic vibrations.
47. Physical method
1. Sunlight:
• Action primarily due to UV rays however, effects vary due to places
Eg: In tropical country, the germicidal effect is better than 4 seasoned countries.
• Bacteria in water are readily destroyed by sunlight.
2. Drying:
• Moisture is essential for growth of bacteria.
• Drying in air has deleterious effect on many bacteria.
• However, spores are unaffected. Therefore, it is not really unreliable.
3. Heat
• Most reliable method of sterilization and should be the method of choice and devided to Dry Heat
& Moist Heat.
48. The factors influencing sterilization by heat:
• Nature of heat-dry or moist
• Temperature and time
• Number of microorganisms present
• Characteristics of organisms –species, strain, sporing capacity
• Type of material from which organism have to be eliminated.
• Killing effect is due to protein denaturation, oxidative damage and toxic effect of
elevated level of electrolytes.
• Killing effect of moist heat due to denaturation and coagulation.
Thermal death time:
• “Minimum time required to kill a suspension of organisms at a predetermined
temperature in a specified environment".
• Thermal death time is inversely proportional to temperature.
• TDT is increased in presence of organic substance, proteins, nucleic acid, starch,
gelatin , sugar , fats, oils.”
49. Dry heat:
Red heat:
• Sterilization is done by holding materials in a bunsen burner flame until they become red hot.
• used to sterilize inoculation, straight wires, wire loops, tips of forceps and spatulas.
Flaming:
• Passed over flame without allowing it to become red hot,
• Items:
• Mouth of test tubes, glass slides, scalpels, needles, cover slips, etit destroys only vegetative microorganism.
Incineration:
• Excellent method for rapid destroying materials.
• reduction in the volume of the wastes.
• final disposal of the hospital.
• Items:
Pathological material, contaminated cloth, animals carcasses, bedding, soiled dressing.
50. Hot air oven:
• The oven is electrical devices used in
sterilization.
• uses dry heat to sterilize articles.
• Generally, they can be operated from
50 to 300 C (122 to 572 F) .
• There is a thermostat controlling the
temperature.
• This is the most widely used method of
sterilization by dry heat.
Items:
• glassware, forceps, scissors, scalpels,
all-glass syringes, swabs, liquid
paraffin, dusting powder, fats, grease.
51. Advantage:
• They do not require water and there is not much pressure build up within the oven, unlike an
autoclave, making them safer to work with.
• Suitable to be use in a laboratory environment.
Disadvantages:
• They are much smaller than autoclaves but can still be as effective.
• Some organisms like prions, may not be killed by them.
52. precautions:
• Glass wares should be dry.
• Oven should not be over loaded.
• Articles are to be arranged in a manner to allow
free air circulation.
• Door of the Oven should be opened after it cools
down (2Hours).
Temerature (c) Holding time(in minutes(
160 45
170 18
180 7.5
190 1.5
53. Moist heat:
Moist means killing of microorganism with hot water/steam
Mechanism/principle:
-Denaturation and coagulation of proteins
Divided into three forms in terms of temperature:
1. Temperature below 100 C.
2. Temperature at 100 C.
3. Temperature above 100 C.
A. Temperature below 100°C
Pasteurization:
• period: 63 C, 30 minutes (holder method) ; or 72 C, 15-20 minutes followed by cooling quickly to 130c or
lower.
Target:-all nonsporing pathogens.
• Eg: mycobacteria, brucellae, salmonella.
• It is applied in dairy products e.g. milk and butter
• Heat labile fluids e.g. serum may be disinfected by heating at 56°C for one hr.
54. B. Temperature at 100°C:
1. Boiling:
• at 100°C for 10– 30 minutes may kill most of vegetative bacteria and some bacterial spores
• It is not suitable for sterilization of surgical instruments
• Addition of small quantity of acid, alkali or washing soda to increase penetration power of
boiling water.
2. Tyndalization:
• method that is used for sterilization of media with sugar and gelatin at 100°C for 30 minutes on
three successive days so as to preserve sugar which might be decomposed at a higher
temperature.
1. Single exposure to steam at 100°C for 20 minutes on three successive days
e.g:
used for egg , serum and sugar containing media.
2. First exposure to steam kills all vegetative bacteria,
second exposure all spores germinate in a favourable medium and are killled on subsequent
occasions.
55. C. Temperature above 100°C
• Heat in the form of saturated steam under pressure is used
• Laboratory apparatus designed to use steam under regulated pressure is
called an autoclave.
• is sufficient to kill all the vegetative forms and spores of the organisms.
Mode of action:
1. Moist heat is responsible for disruption of cell components.
2. Coagulation and denaturation of proteins ( proteins are denatured more
rapidly at lower temp if moisture is present) .
3. Other cell components– cell membrane, ribosome, DNA and RNA also
denatured by moist heat
57. Advantages:
1. It is rapid and effective.
2. It destroys microorganisms more efficiently than dry heat and therefore a shorter
exposure at a lower temperature is possible.
3. It can be used for a large proportion of the official injections.
4. It is supplied with dry saturated steam porous materials and can be sterilized
without damage.
5. Equipment or components of rubber and certain plastics such as nylon and P.V.C
will withstand the conditions.
Disadvantages:
1. Items sensitive to heat cannot be sterilized.
2. It is unsuitable for anhydrous materials such as powders and oils.
3. It cannot be used for injections and articles such as plastics that deteriorate at
115°C.
58. Applications:
1. This method is most essential biocidal agent.
2. It is used for surgical dressings, sheets, surgical and diagnostic equipments,
containers, glassware ,Culture media, suture materials except catgut.
3. To sterilize aq. Solutions e.g. broth .
59. Chemical agents
CHEMICAL AGENTS ACT IN VARIOUS WAYS:
• Protein coagulation.
• Disruption of cell membrane resulting exposure, damage or loss of the
contents
• Removal of free sulphydryl groups essential for the functioning of the
enzymes and
• Substrate competition- a compound resembling the essential substrate of the
enzyme diverts or misleads the enzymes necessary for the metabolism of the
cell and cause cell death
60. ALCOHOLS:
• Ethanol, methanol, isopropyl alcohol are frequently used.
• Act by denaturing proteins.
• They have no action on spores.
• To be effective working concentration is 70-80% in water..
• Protein Slow its action whereas 1% mineral acid and alkali enhances it.
• Methyl alcohol is effective against fungal spores.
• Evaporate, leaving no residue .
Uses
• To disinfect skin prior to injections.
• Methyl alcohol is used to clean incubators and biosafety cabinetsIsopropyl alcohol is
preferred as it is better fat solvent, more bactericidal and less volatile
• Mainly used for disinfection of clinical thermometer.
61. ALDEHYDES:
• They are low molecular weight compounds and act as antimicrobial.
• The most important two aldehydes are formaldehyde and glutaraldehyde.
• 2% solution of glutaraldehyde is known as Cidex which is used for bactericidal and
viricidal in 10 minutes and sporicidal in 3-10 hours.
Mechanism:
• active against the amino group in the protein molecule.
• bactericidal, sporicidial and virucidal.
62. FORMALDEHYDE:
• Excellent disinfectant.
• Formalin (10%) was used extensively to preserve biological specimens and for destroying anthrax spores in hair and wool.
• Irritates mucous membranes, strong odour.
• 10% formalin containing 0.5% sodium tetra borate in water is used to sterilise clean metal instruments.
It is used for :
• Prevention of tissues for histological examinations.
• Sterilization of bacterial vaccines
• Preparation of toxoids from toxins.
Glutaraldehyde:
• Less irritating and more effective than formaldehyde.
• - sterilizing agent: 2% solution of glutaraldehyde (Cidex) which is Bactericidal, tuberculocidal, virucidal in 10 minutes.
• Sporicidal in 3 to 10 hours.
• Commonly used
• to disinfect hospital instruments- cystoscopes, endoscopes, corrugated rubber tubes, face masks, metal instruments,
polythene tubes
63. HALOGENS
lodine:
• Tincture of iodine (alcohol solution) was one of first antiseptics used.
• Combines with amino acid tyrosine in proteins and denatures proteins.
• Stains skin and clothes
• bactericidal, virucidal and fairly active against spores.
Lodophors(povidone-iodine):
• lodine compounds with non ionic wetting or surface active agents.
• It inhibits protein synthesis and oxidizes
• SH groups of amino acids
• Used as skin antiseptic in surgery.
64. • OXIDIZING AGENTS:
• Hydrogen peroxide and peracetic acid.
• H₂O, kills most organisms at 3-6% conc.
• At 10-25% kills even spores.
• Used to disinfectants plastic implants, contact lenses and surgical prosthesis.
Hydrogen peroxide:
• It is effective against most organisms in the concentration of 3-6%.
• However, it kills spores at higher concentrations (10-25%).
• The mode of action is by the liberation of free hydroxyl radical on the decomposition of hydrogen peroxide.
• These free radicals are active ingredients in the disinfection process.
Peracetic Acid:
• Has good sterilization effect on bacteria,particulary common antibiotic resistant bacteria such as methicilin
resistant Staphylococcus aureus, vancomycin resistant Enterococcus and Clostridium defficile.
• sterilization of e.g., endoscopes, arthroscopes.
65. CHLORINE:
• When mixed in water forms hypochlorous acid:
• Cl₂ + H₂O ------> H+ + Cl- + HOCI
• Sodium hypochlorite (NaOCI)
• Is active ingredient of bleach
• Chlorine is easily inactivated by organic materials.
• The organic chloramines are used as antiseptics for dressing wounds.
• Not much useful against sporesUsed to disinfect drinking water, pools, and
sewage
• For household use (bleach) it is used in conc. of 0.2-1%.
66. Chemical methods
A. Gaseous sterilization
• Gaseous sterilization is defined as the destruction of all living
microorganism with a chemical in a gaseous or vapour state
• Material adversely affected by dry and moist heat are then sterilised this
method
• All these gases are toxic to human being above certain concentrations and
exhibit other unpleasant or undesirable side effects
• Ethylene oxide is most widely used than formaldehyde and propiolactone,
in addition to these, various glycols, methyl bromide and alcohol have been
used for room sterilization
67. 1. FORMALDEHYDE GAS
• Excellent disinfectant.
• Formaldehyde in gaseous form is used to fumigate sick rooms, operation theaters,
labs
• It is also a group of alkylating agent .
• It inactivates microorganisms by alkylating the amino acid and sulfhydryl groups of
proteins and ring nitrogen atoms of purine bases
• It is bactericidal agent with poor penetration power.
Applications:
• Disinfection and sterilization of enclosed area such as operation theatres, hospital
rooms, aseptic area and microbiology laboratories
• It kills both vegetative cells and spores
68. 2. Propiolactone:
• Bactericidal agent conc. is 2 to 5 mg/litre
• Lowpenetration power
• It shows irritation and carcinogenic properties, so not recommended for pharmaceutical applications.
3. Ethylene oxide :
• It is colourless liquid with a boiling point of 10.8 C
• Highly inflammable and may be explosive when mixed with air in concentrations greater then 3% .
• Its mixtures with carbon dioxide or fluorinated hydrocarbons (freons) in certain proportions makes
ethylene oxide non-flammable.
• The carbon dioxide and freons act as inert diluents which prevent flammability.
• Effect depend on conc. of gas, temperature, moisture, time, conditions and accessibility of the
microbes.
• Concentration and time relationship commonly used for sterilization is given in table.
69. Mode of action:
• Its power of alkylating the amino, carboxyl, hydroxyl and sulphydryl
groups in the enzymes and protein molecule .
• It reacts with DNA and RNA .
• In this reaction the ring in the ethylene oxide molecule splits and
attaches itself where the hydrogen is present.
70. Applications:
• Powerful sterilizing agent for heat and moisture sensitive materials
• Useful for sterilization of medical and biological preparations, catgut, plastic
equipments, books, clothing and soil.
• Heart lung machine , respirators, dental labs.
71. Filtration
• In order to sterilize solutions which is heat sensitive, filtration is an excellent way to reduce the
microbial population.
• Remove the microbes instead of killing them.
• Depth filters:
• Consists of fibrous or granular materials that have been bonded into a thick layer filled with twisting channels
of small diameter.
• The solution is passed through the filter which is sucked through this layer under vacuum and microbial cells
are removed. The material used mostly is unglazed porcelain, asbestos or other similar materials.
• Membrane filters:
• replaced depth filters in recent times.
• made up of cellulose acetate, cellulose nitrate, polycarbonate, polyvinylidene fluoride, and
other synthetic materials.
• vary in size with pore sizes mostly of 0.2 to 0.5 µm in diameter and used to remove most
vegetative cells, but not viruses, from solutions ranging in volume from 1ml to many litres.
• mostly used to sterilize pharmaceuticals, ophthalmic solutions, culture media, oils, antibiotics
and other heat sensitive solutions.
72. • The other way this method is used is in the laminar flow biological safety cabinets where the air is
sterilized by filtration.
• 𝗈 These cabinets contain high-efficiency particulate air (HEPA) filters, which remove 99.97% of 0.3µm
particles.
• 𝗈 The safety cabinets are most useful as the culturing of any organisms requires contamination free air
to reduce the growth of other undesired organisms or for the preparation of media, examining tissue
cultures.
73. Radiation Sterilization
• Energy transmitted through space in a variety of forms is called
radiation
• Radiation sterilization also called as cold sterilization because ionizing
radiation produce little heat in the material irradiated
• It is suitable for sterilization of heat sensitive substances
• Based on wavelength and penetration power, can be divided into
two categories:
1. Non ionizing radiation:- Less energy and do not disturb the atomic
configuration of the target molecules.
2. Ionizing radiations:- High energy and ionize target molecules.
74. 1.Non ionizing radiation:
• UV radiation.
• effectiveness is limited to surfaces only
• source is UV lamps, called as sterilizing lamps/germicidal lamps
• Vegetative bacteria is susceptible but spores are resistant to UV
light.
Mechanism:
1. UV light is absorbed by the nucleic acids of the cell where it
does greatest damage.
2. These rays induce the production of abnormal nucleotides such
as thymine dimers.
3. These interface in the process of DNA replication.
75. Applications:
1. UV rays are used extensively in hospital rooms, in aseptic filling
rooms, in the pharmaceutical industry (sterile product preparation),
food and dairy industries for treatment of contaminated surfaces.
2. Sterilizing biological fluids such as blood plasma and vaccines.
3. Purification of liquid including milk, fruit, juice, wine and beer.
Disadvantages:
UV rays can damage eyes and are known to cause sun burns and skin
cancers in humans.
76. 2.Ionizing radiation (cold sterilization)
• X-rays, gamma rays and cathode rays are highly lethal to DNA and other
vital cell constituents
• They have very high penetration power and energy.
• The factors that effect the lethal activity of ionizing radiations are as
follows;
a. Oxygen.
b. Protective compounds.
c. Sensitizing agents.
d. pH of culture.
e. Freezing.
f. Moisture and recovery conditions
77. Application:
• antibiotics e.g. benzyl penicillin, streptomycin sulphate, polymyxin
sulphate and vitamins e.g. ascoric abacid .
• inactivate suspensions of influenza, vaccinia, rabies and poliomyelitis
viruses for use as vaccines..
• Sterilizing medical products including drugs, syringes, surgical gloves
and tissues like bone, cartilage, skin and heart valves.
• Foods ,like meat can be sterilized.
78. FORMALDEHYDE GAS
• Excellent disinfectant.
• - Formalin (10%) was used extensively to preserve biological specimens and for
destroying anthrax spores in hair and wool
• Irritates mucous membranes, strong odour.
• -10% formalin containing 0.5% sodium tetra borate in water is used to sterilise clean
metal instruments
• Formaldehyde in gaseous form is used to fumigate sick rooms, operation theaters, labs
Glutaraldehyde:
• Less irritating and more effective than formaldehyde.
• - sterilizing agent: 2% solution of glutaraldehyde (Cidex) which is Bactericidal,
tuberculocidal, virucidal in 10 minutes.
• Sporicidal in 3 to 10 hours.
