Wound Infections
Antibiotic prophylaxis
It has been strongly suggested that
prophylactic antibiotics are overused, (Shanson
1988). This overuse has contributed to the development and spread of bacterial antibiotic resistance as well
as some incidences of nosocomial cross infection. If
prophylaxis is to be used the drugs chosen should have as narrow a spectrum as
possible to prevent undue disruption of normal flora and to reduce the risk of superinfection. The patient may also suffer unnecessary
toxic effects of the drugs and there is always a slight risk of allergic
reactions. These factors mean that each time prophylactic antibiotics are given
the risk from possible infective complications should outweigh the potential
risks of the drugs to the individual patient. In addition there should be
reason to suppose that the antibiotic given is effective against the
potentially infective bacterial strain.
Prophylactic antibiotics used in
trauma and surgery are most effective if the antibiotic is given within three
hours of the initial traumatic or surgical tissue insult. Preferably the
antibiotics will be given as early as possible and in the case of surgery
before the start of the operation. This will mean that there is theraputic tissul levels of
antibiotic when bacterail contamination occurs. Such
prophylaxis should usually be continued after 72 hours, (Westaby,
19 )
Terms
Nosocomial
Prophylaxis
Superinfection
References
Shanson DC (1988) Microbiology
in Clinical Practice, Third edition, Wright, London
Westaby S. 19 , Wound Care, Heinemann,
An infected wound does not heal.
Any poorly healing wound should be
swabbed for culture.
Types of wound
Clean
Surgical wounds not involving opening
potentially infecting cavities
Clean-contaminated
Operative wounds in which the gut
respiratory or GU tract is entered, usually without contamination
Contaminated wound
Fresh traumatic wounds
Wounds coming into contact with
non-purulent infection eg. cholecystitis
Wounds entering the colon
Dirty and infected wounds
Wounds infected from the outside or
inside the patient
What are the clinical features of
wound infection?
Local Systemic
Inflammation Malaise
Heat Pyrexia
------ dehydration
Pain Tachycardia
proportional to pyrexia
Redness Pyrexia/
febrile/rigours
Swelling Metastatic infection
Loss of function Risk
of bacteraemia, septicaemia and death
Pus, eg. from suiture sites or wound drain Leucocytosis
Purulent discharge Anorexia
Non-healing Enlarged
lymph nodes
Cellulitis Lymphatic
streaking
Necrotic tissue
Smell
Wound breakdown
Dehiscencs
Wound enlargement
Tender to palpation
Green appearance indicates pseudomonas
Fever alone may have many other
causes, deep seated infection may give rise to systemic signs first. Learn to
distinguish between normal redness in granulation tissue and inflammatory
redness.
Depressed cardiac function from toxins
with clostridia
Peripheral vasodilation
- low BP
Renal and respiratory complications
Distinguish between wound Infection
and wound colonisation.
Infection -
A wound with clinical features of infection. In this situation there is
clinical evidence of infection and the wound will usually grow the infective
agent on culture.
Colonisation -
A colonised wound may grow bacteria on culture but has no clinical
features of infection. Bacterial culture may produce laboratory evidence of the
presence of bacteria in the absence of the clinical features of infection. Most
chronic wounds are colonised whereas most surgical wounds are not.
Give clinical applications of the
above differentiation
Infection - Infection inhibits or prevents healing.
Cultures should be taken from clinically infected wounds to optimise treatment.
Colonisation - Colonisation does not significantly
inhibit healing. Cultures should not normally be taken from wounds in the
absence of clinical features of infection, "to find out what is
there", this is a waste of resources and has no clinical application.
Which wounds are in danger of becoming
infected?
All wounds may potentially become infected due to
disruption of the bodies protective barrier. Westaby
claims that wounds effecting the abdomen, thigh, calf and buttock are
especially susceptible while the face, scalp and thorax are affected less
frequently.
What factors influence the likelihood
of a wound becoming infected?
You may have thought of several however you may
wish to take the factors you have considered and try to fit them into the
following classifications
Contamination Bacterial
Environment Patient
resistance
The more contamination Prolonged treatment
procedures Immune
status
the greater the infection
Presence/absence of oxygen Age
risk Presence of
medium/substrates Nutritional
status
Extent and nature of the
wound
Anergy
Haematoma
Inflammatory
bowel disease Tissue damage by crushing
Diabetes
Presence of foreign material, (big
factor) Anaemia
Dehydration
Shock
Lowest incidence of infection is in late teens and
early 20s. Children have a slightly higher incidence of infection. After the 20
the incidence progresses with increasing age.
Wound infection = number or organisms x virulence
host resistance
Where may bacteria which contaminate a
wound come from?
You may have thought of several possibilities, try
to classify your ideas under the following headings. Endogenous means from the
patient themselves, exogenous means from without the patient.
Endogenous Exogenous
Patents normal bacterial flora, becoming
pathogenic Cross
infection
in the wound. From
Staphylococcal carrier
The most common bacteria to cause
wound infection are from the skin and gut. Staphylococcus aureus
and Staphylococcus epidermis are found on the skin. Staphylococcus aureus is also found in the upper respiratory tract
Might these organisms also be found in
the air? If so why?
Yes - dead skin cells are always flaking off into
the air. Also Staphylococcus and Streptococcus may be exhaled passed on through
coughing and sneezing and by touch.
Give a clinical application from your
answer
Do not open wounds to dusty air, eg. after hospital bed making
What does virulence mean?
The organisms ability to create infection despite
the body's defence mechanisms
Is nosocomial
wound infection a problem?
About 10% of patients acquire some kind of
infection while in hospital, about a quarter of these are wound infections
What is the relationship between area
of superficial skin loss and wound infection? Give a rationale for your answer.
The more skin loss the greater the risk due to the
increased opportunity for wound colonisation
What is the relationship between
debilitation and risk of wound infection? Give a rationale for your answer.
Debility predisposes to infection risk. Lack of
mobility reduces blood circulation and also leads to an impaired immune
response.
What are aerobic and anaerobic
bacteria?
Aerobic -
need oxygen to live
Anaerobic -
are killed by the presence of oxygen
Eg. Clostridium tetani
-
often in the soil in spore form
Clostridium
welchii -
from soil or gut, infection causes gas gangrene
How may the risks of anaerobic
infection be reduced?
Usually these infections gain access to the wound
from dirt in the environment, therefore wound exploration and cleaning are
vital. Also debridment and follow up wound cleaning
may help. Sometimes allow to heal by secondary intention. Ensure all foreign
bodies are removed.
So infection may be airborne, auto,
cross or from contaminated equipment
List nursing measures to prevent these
forms of wound contamination.
Airborne infection
Dressing to cover wound
Short exposure of wound to ward air - collection
of bacteria on wound is proportional to time of exposure.
Auto-infection
Skin cleaning
Prevent outside contamination, eg
urine, faeces
Cross infection
Cross infection between patients or vectored by
staff.
Isolation if indicated.
Correct waste disposal, isolation of soiled and
contaminated linen.
Barrier nursing / reverse barrier nursing,
protective clothing etc.
Treat infected wounds after clinically normal
wounds
Generally clean environment
Good staff personal hygiene, hand washing etc.
Avoid hand contact with eyes, nose, mouth and
genitalia
Combinations of the above modes of
contamination
Avoid interference with dressing
Prevent moist pathways, eg
from exudate
Asepsis of dressings and any instruments uses
Early recognition of infections
Remove source of infection
Extra care when using invasive devices
When and how should necrotic material be
removed from a wound?
Basically dead tissue is no good and should be
removed unless it forms an inert protective layer, with no fluid collected
beneath it. Normally wounds are debrided using
topical debriding agents or surgical excision
Always check perfusion of a wound.
How may wound perfusion be assessed?
Colour, capillary refill, pulses distal to the
wound, level of pain.
Why is necrotic tissue a problem?
Acts a nutrient culture medium for bacteria. Poor
blood supply means white cells can not readily get to the area.
Which patients are at increased risk
of infection for intrinsic reasons?
The following factors may lead to immuno-compromise, HIV AIDS, steroids, very old and very
young, immuno-suppressants, malignancies, those with
other infections.
What are the longer term effects of
wound infection
Longer hospital stay/need for more medical/nursing
intervention
More time off work
Formation of more scar tissue
Change in body image, eg. facial scaring
Loss of function of part of body eg. hand
Amputation
Chronic infections, eg. osteomylitis
Antibiotic use/prophylaxis
Most wounds do not need routine
antibiotic prophylaxis.
Which wounds will need prophylactic
antibiotics?
Those involving known infection or opening of the
gut
What factors and procedures will
determine antibiotic choice?
Culture and sensitivity to give a narrow spectrum,
effective antibiotic
What is meant by the following terms
Resistance
The ability of a bacterial strain not to be killed
in the presence of an antibiotic
Broad spectrum
An antibiotic which is effective against a wide
range of bacterial types
Narrow spectrum
An antibiotic which is effective against a narrow
range of bacterial types
Multiple resistance strains may emerge
from the indiscriminate use of topical antibiotics
Bacterial cultures
What is the ideal material to send for
culture?
Pus, exudate or tissue
is more useful than a swab. In deep wounds check with the lab re. type of
specimen, storage and transportation.
What may cause a false positive
culture result?
A superficial swab may identify bacteria
colonising the wound but not causing the infection.
What may cause a false negative
culture result?
A swab which fails to culture bacteria which are
in fact causing infection, perhaps deeper in the wound. Anaerobes are often
difficult to culture from routine swabs.
What is the difference between a
qualitative and a quantitative culture?
Qualitative analysis will only identify the
organisms present not the number or organisms. Biopsy will identify numbers,
infection is defined as 105 organisms per gram of tissue or per ml
of wound fluid.
Leg Ulcers
In some chronic wounds such a leg
ulcers heat pain and redness may be a part of the normal healing process so
infection needs to be assessed using other criteria
Chronic wounds may have high numbers
of bacteria per gram of tissue, with no signs of infection and still go on to
heal
Subsequent culture of leg ulcers
reveals changes in the type of bacterial cultured (82% of ulcers), so it seems
than the colonising bacteria change over time.
Healing in leg ulcers in independent
of bacteria cultured on surface swabs.
It seems likely that Staphylococcus aureus, B - haemolytic streptococcus and pseudomonas have a
detrimental effect on ulcer healing.
The following criteria are useful in
determining infection or otherwise in leg ulcers
* lack
of progress towards healing
* very
friable granulation tissue with an unhealthy red colour
* increased
pain
* increased
exudate
Principles of treatment
Systemic
Reassurance and encouragement
Nutrition
Hydration
Correct other conditions eg.
diabetes
Antibiotics
Metronidazole
Local
Keep wounds open
Open surgical infected wounds
Ensure good wound drainage
Pack if not drained by surgical drains
Intermittent topical irrigation
Debridement
Drainage of abscesses
Allow wounds to close by contraction
Keep dressings changed to keep dry
Avoid adhesive tapes on excoriated skin
Local moist heat may improve circulation and lymph
flow
Possible topical antibiotics
Septicaemia
Specific intravenous antibiotics
Cellulitis
Intravenous or oral antibiotics for
long enough to establish resolution of symptoms
Local infections causing delays in
healing
There should not be widespread,
indiscriminate use of topical antiseptics as these do not seem to be positively
correlated with improved healing, and
there is some evidence that they may adversely effect healing in certain
circumstances
Examples of treatment options
Indicate how you would manage the
examples below
Infected pressure sore - Escherichia
coli, Bacteroides, Staphylococcus aureus,
(75 year old woman)
Irrigation with 0.9% saline to remove debris and faecal
contamination
Oral flucloxacillin -
prevent spreading of local infection
Topical metronidazole
Hydrogel - (to control odour)
Possible use of hydrocolloids and topical
antiseptics
Non-healing post operative pilonidal sinus (23 year old man) with unhealthy coloured,
friable granulation tissue.
Oral metronidazole and
erythromycin
Possible alginate dressings
Post operative removal of metastatic malignant melanoma, (62 year old woman). Swab
revealed MRSA. Wound showing signs of healing.
Because wound is healing the MRSA is probably only
colonising the wound
Apply topical mupirocin
to prevent spread of MRSA
Change dressing frequently
Possible iodine impregnated dressings, ( eg. inadine)
Possible intravenous vancomycin,
topical iodine or silver sulphadiazine
Four month history of foot ulcers from
ill fitting shoes in a patient with IDDM, (57 year old man)
Oral flucloxacillin
X Ray to identify bony involvement
Surgery for removal of dead infected soft tissue
and bone - for osteomyelitis
Wound drainage
Patient with recurrent soft tissue
infections in the thigh, green appearance to wound, (49 year old woman)
Green = pseudomonas infection
Antiseptics
Possible Silver sulphadiazine,
Acetic acid, Tea-tree oils
Particular problems
Necrotising fasciitis
A serious spreading infection
involving the fascial planes
Haemolytic streptococci or Staphylocci
Causes tissue necrosis and gangrene
Treated with excision of the whole
area of fascial involvement and Penicillin
Gas gangrene
Anaerobic infection of muscle
Toxaema
Local oedema and gas bubbles
Swelling
Discharges of foul brown fluid
Blotchy and purple overlying skin
becoming purple/black
Amputation may prevent death
Large doses of penicillin
Mortality of 25 - 40%
Human bites
Streptococci staphyloccocci
and spirochetes
Debridement required
Cleaning and immobilisation
Systemic antibiotics often penicillin
References and reading
Shanson DC (1988) Microbiology
in Clinical Practice, Third edition, Wright, London
Westaby S. 19 , Wound Care, Heinemann,
Gilchrist B (1996) Wound Infection, Journal
of Wound Care, vol. 5 no. 8 Sept.
Harding KG (1996) Wound Infection, Journal of
Wound Care, vol. 5 no. 8 Sept.
David JA (1987) Wound Management, Martin Dunitz
An infected wound does not heal.
Any poorly healing wound should be
swabbed for culture.
Types of wound
Clean
Surgical wounds not involving opening
potentially infecting cavities
Clean-contaminated
Operative wounds in which the gut
respiratory or GU tract is entered, usually without contamination
Contaminated wound
Fresh traumatic wounds
Wounds coming into contact with
non-purulent infection eg. cholecystitis
Wounds entering the colon
Dirty and infected wounds
Wounds infected from the outside or
inside the patient
What are the clinical features of
wound infection?
Local Systemic
Fever alone may have many other
causes, deep seated infection may give rise to systemic signs first. Learn to distinguish
between normal redness in granulation tissue and inflammatory redness.
Depressed cardiac function from toxins
with clostridia
Peripheral vasodilation
- low BP
Renal and respiratory complications
Distinguish between wound Infection
and wound colonisation.
Infection -
Colonisation -
Give clinical applications of the
above differentiation
Infection - .
Colonisation -
Which wounds are in danger of becoming
infected?
What factors influence the likelihood of
a wound becoming infected?
Contamination Bacterial
Environment Patient
resistance
Wound infection = number or organisms x virulence
host resistance
Where may bacteria which contaminate a
wound come from?
Endogenous Exogenous
The most common bacteria to cause
wound infection are from the skin and gut. Staphylococcus aureus
and Staphylococcus epidermis are found on the skin. Staphylococcus aureus is also found in the upper respiratory tract
Might these organisms also be found in
the air? If so why?
Give a clinical application from your
answer
What does virulence mean?
Is nosocomial
wound infection a problem?
What is the relationship between area of
superficial skin loss and wound infection? Give a rationale for your answer.
What is the relationship between
debilitation and risk of wound infection? Give a rationale for your answer.
What are aerobic and anaerobic
bacteria?
How may the risks of anaerobic
infection be reduced?
So infection may be airborne, auto,
cross or from contaminated equipment
List nursing measures to prevent these
forms of wound contamination.
Airborne infection
Auto-infection
Cross infection
Combinations of the above modes of
contamination
When and how should necrotic material
be removed from a wound?
Always check perfusion of a wound.
How may wound perfusion be assessed?
Why is necrotic tissue a problem?
Which patients are at increased risk
of infection for intrinsic reasons?
What are the longer term effects of
wound infection
Antibiotic use/prophylaxis
Most wounds do not need routine
antibiotic prophylaxis.
Which wounds will need prophylactic
antibiotics?
What factors and procedures will
determine antibiotic choice?
What is meant by the following terms
Resistance
Broad spectrum
Narrow spectrum
Multiple resistance strains may emerge
from the indiscriminate use of topical antibiotics
Bacterial cultures
What is the ideal material to send for
culture?
What may cause a false positive
culture result?
What may cause a false negative
culture result?
What is the difference between a
qualitative and a quantitative culture?
Leg Ulcers
In some chronic wounds such a leg
ulcers heat pain and redness may be a part of the normal healing process so
infection needs to be assessed using other criteria
Chronic wounds may have high numbers
of bacteria per gram of tissue, with no signs of infection and still go on to
heal
Subsequent culture of leg ulcers
reveals changes in the type of bacterial cultured (82% of ulcers), so it seems
than the colonising bacteria change over time.
Healing in leg ulcers in independent
of bacteria cultured on surface swabs.
It seems likely that Staphylococcus aureus, B - haemolytic streptococcus and pseudomonas have a
detrimental effect on ulcer healing.
The following criteria are useful in
determining infection or otherwise in leg ulcers
lack of progress towards healing
very friable granulation tissue with
an unhealthy red colour
increased pain
increased exudate
Principles of treatment
Give examples of the following types
of treatment
Systemic
Local
Septicaemia
Specific intravenous antibiotics
Cellulitis
Intravenous or oral antibiotics for
long enough to establish resolution of symptoms
Local infections causing delays in
healing
There should not be widespread,
indiscriminate use of topical antiseptics as these do not seem to be positively
correlated with improved healing, and
there is some evidence that they may adversely effect healing in certain
circumstances
Examples of treatment options
Indicate how you would manage the
examples below
Infected pressure sore - Escherichia
coli, Bacteroides, Staphylococcus aureus,
(75 year old woman)
Non-healing post operative pilonidal sinus (23 year old man) with unhealthy coloured,
friable granulation tissue.
Post operative removal of metastatic malignant melanoma, (62 year old woman). Swab revealed
MRSA. Wound showing signs of healing.
Four month history of foot ulcers from
ill fitting shoes in a patient with IDDM, (57 year old man)
Patient with recurrent soft tissue
infections in the thigh, green appearance to wound, (49 year old woman)
Particular problems
Necrotising fasciitis
A serious spreading infection
involving the fascial planes
Haemolytic streptococci or Staphylocci
Causes tissue necrosis and gangrene
Treated with excision of the whole
area of fascial involvement and Penicillin
Gas gangrene
Anaerobic infection of muscle Toxaema
Local oedema and gas bubbles Swelling
Discharges of foul brown fluid
Blotchy and purple overlying skin
becoming purple/black
Amputation may prevent death Large
doses of penicillin
Mortality of 25 - 40%
Human bites
Streptococci staphyloccocci
and spirochetes Debridement required
Cleaning and immobilisation Systemic
antibiotics often penicillin