Medical Chronicle November/December 2013 | Page 48

WOUND CARE
signals within clusters increase
and a critical level (or ‘quorum’) is
exceeded, gene expression within the
cells changes and biofilm development
is initiated or accelerated. The
final stage of biofilm formation and
maturation is known as ‘dispersion’,
enabling the biofilm to spread and
colonise new surfaces.

To swab or not to swab?
Swabs should be collected only when
clinical criteria point to a wound
infection and before any antimicrobial
interventions have been initiated.
However, superficial sampling is
considered to be of little clinical value
and generally unreliable for identifying
the pathogens responsible for deeper
infection.
In order to remove superficial debris
and surface contaminants, as well as
provide more specific results, thorough
cleansing of the wound bed with sterile
saline or water should be undertaken
prior to microbiological sampling.
Preferred clinical specimens include
aspirate from a sinus or abscess, while
a tissue biopsy or curettage from
the deep wound bed compartment is
regarded as the reference standard
for diagnosing infection. Ensure the
specimen reaches the laboratory
within three hours, or refrigerate it if a
delay is expected.
The following species will invariably
be cultured from longstanding wounds:
Enterobacteriaceae, Enterococci,
Staphylococcus aureus and/or
MRSA, Klebsiella, Acinetobacter and
Pseudomonas species, and anaerobes
(underneath slough and dry eschar).
The presence of >15 leucocytes/
mm3 on direct microscopy may
be suggestive of an inflammatory
process or infection. Semi-quantitative
laboratory analysis reported as a
colony count >105cfu’s/g tissue
(100 000 colony-forming units) may be
a ‘predictor’ of critical colonisation or
local wound infection.
Liaison with the medical
microbiologist is advisable
where there is a history of, or
suspected drug resistance especially extended spectrum
beta lactamase (ESBL+ve) and
carbapenemase (CRE) producers if the resources are available, PCR
methods are able to detect most
species of pathogens in a wound
in a matter of hours, including
antimicrobial resistance.

Topical antimicrobial agents
active in biofilms
The increasing prevalence of antibioticresistant microbial strains and
persistent nature of biofilms presents
an ongoing challenge for treating
infected and colonised wounds.
Because bacteria need to be
metabolically active for antibiotics to

act, hibernating bacteria in biofilms
are unaffected by antibiotics that
would normally kill active bacteria.
Research has shown that the lowest
concentration required to kill or
eliminate bacterial biofilm for many
antibiotics actually exceeds the
maximum prescription levels for the
antibiotics. So, standard doses of
antibiotics, which effectively kill the
normally susceptible bacteria when
grown in suspension in a clinical
laboratory, may have little or no
antimicrobial effect on the same
type of bacteria in biofilm form in
the patient.
The most widely used broadspectrum topical microbicidal agents
are iodine, honey, PHMB and silver
- available in a range of formulations
and carrier mediums. Although there
currently appears to be no ‘hard and
fast’ rule as to which antimicrobial
is preferable as a first-line product,
practical and economic considerations
are required based upon patient or
caregiver ability, the frequency of
dressing changes required (e.g. heavily
exuding wounds) and, importantly, a
considered holistic assessment as
to whether a topical antimicrobial is
indeed necessary.

1. Biofilm penetrative and
reducing agents
• Flavonix® cytoflam gel: A combination of agents that targets inflammation and bacterial biofilm formation,
by reducing inflammatory cytokines
and increasing growth factors.
• Prontosan® solution and wound
gel: A combination of a broadspectrum synthetic biguanide
Polyhexamethylene biguanide
(PHMB), and Betaine (a surfactant
cleanser). It disrupts lipoproteins in
biofilm (thus lowering the surface
tension), interferes with chemical
signalling (‘quorum sensing’) and
promotes effective debridement.

2. Topical antiseptics
The principle site of action is
the bacterial cell membrane, in
concentrations which are not cytotoxic,
chemically stable in the presence of
organic matter (eg. blood, pus) and
preferably in a sustained release form.
• Polyhexamethylene biguanide
(PHMB) solution as above.
• Chlorhexidine gluconate, povidone
and cadexomer iodine (Iodosorb?