diagnosis and treatment of infected skin ulcers...diagnosis and treatment of infected skin ulcers...
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Richard Everts
Infectious Diseases Physician/Microbiologist
Nelson Bays Primary Health
Diagnosis and treatment
of infected skin ulcers
Diagnosis
What is infection?
Disease presents as a continuum or spectrum of
symptoms, signs and other features
E.g. Asthma, mental illness
Neisseria meningitidis
Asymptomatic bacteriuria
What is infection?
A point in the continuum from harmless
contamination to invasive disease at which the
patient has symptoms, signs or complications/
problems (e.g. poor healing).
Harmless contamination
↓
Colonisation
↓
Heavy colonisation – mild immune reaction
↓
Invasive disease – major immune reaction
Not infection
Infection
What is infection?
A point in the continuum from harmless
contamination to invasive disease at which the
patient has symptoms, signs or complications/
problems (e.g. poor healing).
Harmless contamination
↓
Colonisation
↓
Heavy colonisation – mild immune reaction
↓
Invasive disease – major immune reaction
Not infection
Infection
Immune reaction
Cytokines, dilated blood vessels, leaky capillaries,
migration of cells, debris
Pain Swelling Redness Pus
Lymphangitis Lymphadenitis
Malaise Fever AbN vital signs CRP rise
What is CRP?
C-reactive protein
Made by the liver in response to any tissue
damage or inflammation
Infection
Trauma
Auto-immune/connective tissue disease (RA, PMR,
Crohn’s disease)
Cancer
A common laboratory test (cost $7-10)
Most strikingly elevated in bacterial infection.
CRP to diagnose infection
CRP = 195 CRP = 13
Harmless
transient
contamination
Thanks to Susie Wendelborn
Colonisation
Colonisation
Swabbing a non-infected ulcer is like
picking your nose in public...
You need to think what you might do
if you find something.
Haemophilus ducreyi
H. ducreyi •Causes chancroid
(STI) in adults
•2007 Auckland: 3
children from
Samoa with skin
ulcers
•2013 PNG: 90
chronic skin ulcers:
42 H. ducreyi; 19
yaws; 12 both
•Identify by PCR,
not culture
Yaws
Infection
Infection
Infection
Infection
Infection
Infection
Why swab an infected ulcer?
If suspect MRSA
Recent previous positive
If flucloxacillin is failing
If there is frank pus.
(And take blood cultures if febrile.)
Skin cancer removed and grafted. Graft broke down.
A little red, goopy, sore, not healing.
Is it infected?
Clinical signs alone?
Which signs? (Thermal imaging?????) Patient
measures temperature? Test CRP?
Taking a sample for culture? If so, how?
Trial of antibiotics? If so, which antibiotic?
Collecting a sample
Tissue best (but hassle, invasive)
Properly collected quantitative swab is
reasonable alternative
‘Expert’ opinion:
Clean site by wiping or irrigating with sterile water or
saline to clear debris and exudate
Debride if necrosis/eschar
Moisten swab first if wound/ulcer-bed dry (??)
Levine method: twirl with pressure on 1 cm2 area
Patricia Bonham. Swab cultures for diagnosing wound infections:
A literature review and clinical guideline.
J Wound Ostomy Continence Nurs 2009; 36(4): 389-95
WARNING:
LOW-DATA TOPIC
Assessing the swab result
Surface swab culture correlates somewhat with
biopsy culture J Trauma 1976; 16:89-94 and many others......
Gram stain microscopy
Lots of white cells?
Lots of pathogenic bacteria?
Culture
Pure or heavy growth?
Pathogen?
Who robbed the bank?
Pseudomonas aeruginosa
Coagulase-negative
staphylococci
Coliforms (E. coli,
Klebsiella etc.)
Anaerobes Staphylococcus aureus or
Group A streptococcus
(Streptococcus pyogenes)
Microscopy:
No leucocytes seen
Moderate GPC seen
Culture:
Heavy growth of normal
skin flora
Colonisation
Microscopy:
No leucocytes
Moderate GNB
Occasional GPC
Culture:
(1) Moderate growth
of mixed coliform
bacilli
(2) Moderate growth
of P. aeruginosa
(3) Scanty growth of
Staphylococcus
aureus
Colonisation
(but need to watch!)
Microscopy:
Scanty leucocytes
Scanty GNB
Occasional GPC
Culture:
(1) Heavy growth of
E. coli
Heavy colonisation – may be
contributing to non-healing
Microscopy:
No leucocytes
Moderate GPC
Moderate GPB
Scanty GNB
Culture:
(1) Heavy growth of
mixed coliforms
(2) Moderate growth of
Enterococcus spp.
(3) Moderate growth of
anaerobes
Colonisation
Microscopy:
Moderate leucocytes
Moderate GPC
Culture:
(1) Heavy growth of
Staphylococcus aureus
(2) Scanty growth of skin
flora
Infection
Microscopy:
Moderate leucocytes
Moderate GPC
Moderate GNB
Culture:
(1) Heavy growth of
Staphylococcus
aureus
(2) Moderate growth of
mixed coliform bacilli
(3) Moderate growth of
coagulase-negative
staphylococci
Infection (S. aureus) and heavy
colonisation (coliforms) – with
symptoms (pain) and complications
(graft failure, not healing)
Summary - diagnosis
No symptoms or signs of infection –
don’t swab, no need for systemic
antibiotic treatment
Uncertain – consider correctly taken
swab and assess result carefully; or trial
of systemic antibiotic treatment Flucloxacillin > cephalexin/cefazolin >
clindamycin
Obviously infected – swab in selected
cases, give systemic antibiotic
treatment as above.
Treatment
Treatment of infected ulcers
Treat underlying cause.
Invasive disease
Choice of systemic antibiotic
Empiric – cover S. aureus and
beta-haem strep – e.g.,
flucloxacillin
Targeted
Route and dose of systemic
antibiotic
Initially high-dose (IV or
probenecid-boosted)
Duration – varies.
Density of bacterial tissue
invasion correlates with
delayed healing
Antimicrobial Agents and
Chemotherapy 1964; 10: 147
Symptoms and signs of
invasive infection
Treatment of heavy colonisation
What evidence is there for doing this?
1. Surface colonisation correlates somewhat
with tissue invasion on biopsy.
2. Topical antibacterial agents probably improve
healing even in the absence of features of
invasive infection.
Treatment of heavy colonisation
Debride necrotic/devitalised material/eschar
Remove slough/goop (toxins, WC, bacteria)?
Dressings (none better than any other)
Topical antibacterial agents Silver sulphadiazine
Cadexomer iodine
Povidone iodine
Honey
Peroxide
Chlorhexidine
Others.....
Do topical antibacterial products
or dressings kill bacteria?
Kill bacteria in lab? – YES
Kill bacteria on surface of ulcer – YES (for how
long?)
Kill bacteria deep in tissues – YES Chronic pressure ulcers. Test = reduce to < 105/g in biopsy
in 3 weeks. Success rates: SSD (n = 15) 100%; saline
(n=14) 79%; pov-iod (n=11) 64%. J Am Geriatr Soc 1981; 29(5): 232-
Improve signs of infection – YES Chronic wounds (n=34). Test = infection checklist score
change in 4 weeks. Silver alginate dressing 3.3 to 1.3;
control 2.2 to 2.3. Advances in Skin and Wound Care 2012; 25(11): 503-8
Do topical anti-bacterial products
or dressings cause damage?
Allergic reaction? – OCCASIONALLY
Damage cells (e.g. fibroblasts) in-vitro models
SSD – YES
Chlorhexidine – YES
Povidone iodine – YES
But in-vivo??
Anti-microbial resistance – SOME YES
The ultimate test....
Randomised controlled trials of ulcer healing
Requirements:
Independent investigator (publication bias,
assessment of outcome bias etc.)
Ethics approved
Patienti consent, ability to withdraw if choose
Randomised
Reasonable numbers
Objective outcome scoring....
Topical anti-bacterial agents for
venous ulcer healing Cochrane Database Syst Rev 2014
45 RCTs, 53 comparisons, 4486 patients
Poor design - small, high risk of bias, different baseline status,
different duration of treatment....
Overall – difficult to know if effective or not!
Results:
Cadexomer iodine (12 RCT) – likelihood of complete healing
at 4 to 12 weeks improved by RR 2.17 compared with
standard care
No evidence of benefit for povidone iodine (7 RCT), honey (2
RCT) Cochrane review of honey 2015 – may help burns and post-op wounds
Surrogate markers only for silver (12 RCT – size, not %
healed) and peroxide (4 RCT.)
Thanks
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