Wound
infection is commonly observed after surgery and trauma but
is difficult to diagnose and poorly defined in terms of objective
clinical parameters. The assumption that bacteria in a wound correlate
with infection is false; all wounds contain microorganisms, but not
all wounds are clinically infected. This makes it difficult for clinicians
to determine true wound infection, especially in wounds with pathogenic
biofilms. If an infection is not properly treated, pathogenic virulence
factors, such as rhamnolipids from
Pseudomonas aeruginosa
, can modulate the host immune response and cause tissue breakdown.
Life-threatening sepsis can result if the organisms penetrate deep
into host tissue. This communication describes the sensor development
for five important clinical microbial pathogens commonly found in
wounds:
Staphylococcus aureus
,
P. aeruginosa
,
Candida albicans/auris,
and
Enterococcus faecalis
(the
SPaCE
pathogens). The sensor contains liposomes encapsulating
a self-quenched fluorescent dye. Toxins, expressed by
SPaCE
infecting pathogens in early-stage infected wounds, break down the
liposomes, triggering dye release, thus changing the sensor color
from yellow to green, an indication of infection. Five clinical species
of bacteria and fungi, up to 20 strains each (totaling 83), were grown
as early-stage biofilms in ex vivo porcine burn wounds. The biofilms
were then swabbed, and the swab placed in the liposome suspension.
The population density of selected pathogens in a porcine wound biofilm
was quantified and correlated with colorimetric response. Over 88%
of swabs switched the sensor on (10
7
–10
8
CFU/swab). A pilot clinical study demonstrated a good correlation
between sensor switch-on and early-stage wound infection.
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