Download Dr Richard Everts - `Diagnosis and treatment of infected skin ulcers`

Diagnosis and treatment
of infected skin ulcers
Richard Everts
Infectious Diseases Physician/Microbiologist
Nelson Bays Primary Health
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).
Not infection
Infection
Harmless contamination
↓
Colonisation
↓
Heavy colonisation – mild immune reaction
↓
Invasive disease – major immune reaction
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).
Not infection
Infection
Harmless contamination
↓
Colonisation
↓
Heavy colonisation – mild immune reaction
↓
Invasive disease – major immune reaction
Immune reaction
 Cytokines, dilated blood vessels, leaky capillaries,
migration of cells, debris
Pain
Swelling
Lymphangitis
Malaise
Fever
Redness
Pus
Lymphadenitis
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
Colonisation
Thanks to Susie Wendelborn
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
WARNING:
LOW-DATA TOPIC
 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
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
Coliforms (E. coli,
Klebsiella etc.)
Coagulase-negative
staphylococci
Anaerobes
Staphylococcus aureus or
Group A streptococcus
(Streptococcus pyogenes)
Colonisation
Microscopy:
No leucocytes seen
Moderate GPC seen
Culture:
Heavy growth of normal
skin flora
Colonisation
(but need to watch!)
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
Heavy colonisation – may be
contributing to non-healing
Microscopy:
Scanty leucocytes
Scanty GNB
Occasional GPC
Culture:
(1) Heavy growth of
E. coli
Colonisation
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
Infection
Microscopy:
Moderate leucocytes
Moderate GPC
Culture:
(1) Heavy growth of
Staphylococcus aureus
(2) Scanty growth of skin
flora
Infection (S. aureus) and heavy
colonisation (coliforms) – with
symptoms (pain) and complications
(graft failure, not healing)
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
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



Symptoms and signs of
invasive infection
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
Treatment of heavy colonisation
 What evidence is there for doing this?
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.
1.
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