Past experience has shown that the hospital itself
can be a source of bacterial infection among patients,
sometimes of a serious nature. It is believed that
at least one third of such infections can be prevented
if adequate measures are taken. Studies have shown
that patients contaminate medical instruments like
stethoscopes, blood pressure cuffs and otoscopes and
medical personnel themselves, making them vehicles
for further bacterial contamination of men and material.
Studies were conducted recently to find out the potential
of dermatoscopes to serve as one such vehicle of patient
The aim of the studies was three fold.
- To determine the potential of dermatoscopes
as vehicles of bacterial transmission and the range
of bacteria present in them, after examination of
- To determine the effectiveness of isopropyl
alcohol as a disinfectant.
- To determine the effectiveness
of disposable transparent lens covers in preventing
Method: The lenses and shafts of dermatoscopes were
examined and cultures taken after they were used
on 39 patients – 19 outpatients and 20 inpatients.
The dermatoscopes were then cleaned with isopropyl
alcohol swabs for at least 5 seconds and dried in
air for 1 minute. An additional culture was then
After disinfection, dermatoscopic examination was
done on patients, using disposable lens covers that
covered the lens and shaft. Cultures from the covers
were taken before and after examination. Furthermore,
image quality with and without lens covers was compared.
Results: Nineteen types of bacteria were found from
dermatoscopes after examining inpatients and 10 types
were found in samples from outpatients. In both samples
staphylococcus epidermidis were by far the most common.
Staphylococcus aureus was found only in samples from
inpatients. Fortunately, methicillin-resistant staphylococci
were not found in either sample.
It was observed that both the lenses and the shafts
of the dermatoscopes contained bacteria depending
on the patient environment. In outpatients, the bacteria
from their skin, known to be potentially pathogenic,
were found on the surface of the devices. Staphylococcus
aureus were repeatedly detected on the devices after
examining inpatients. These observations seemed to
show that dermatoscopes could be vehicles for onward
transmission of bacteria to other patients.
It was seen that disinfecting the lenses and shafts
of the devices with 70% isopropyl alcohol significantly
reduced the bacterial counts. No statistically significant
difference was observed between cultures taken from
inpatients and those taken from outpatients. Propyl
alcohol, which was not used in this study, could also
be a good disinfectant since its well known as one
of the most effective cleaning agents of membranes
of stethoscopes under routine conditions.
In all examinations done with disposable polythene
lens covers, no bacteria were found either on the
lenses or on the shafts. In all samples taken from
these examinations no bacterial growth was observed
in the cultures. The studies produced strong evidence
of the effectiveness of these lens covers to almost
eliminate bacterial contamination of the dermatoscopes.
Replacement of these lens covers after each examination
should significantly improve safety.
No difference in quality was found between images
taken without lens covers and those taken with lens
covers. Nor was any reduction in optical resolution
observed in images taken with lens covers, further
strengthening the case for their use.
Study limitations: These studies had some limitations.
The relatively small number of dermatoscopes used
in the studies may not have fully estimated the true
extent of bacterial contamination. Again, because
of the small number of devices used, the comparison
between the effectiveness of cleaning agents and lens
covers may not be very accurate. Finally, since the
study comparing image qualities with and without lens
covers was not blinded, chances of investigator bias
creeping in, and affecting objectivity, cannot be
The above limitations notwithstanding, the study
provided enough evidence to conclude that dermatoscopes
do get contaminated by bacteria from patients during
examination. It further shows conclusively that simply
cleaning the device with isopropyl alcohol considerably
reduces bacterial contamination, a fact that hospitals
and dermatologists should note! It was observed by
the study authors that cleaning was not adequate even
in emergency departments of hospitals.
The most significant observation was that lens covers
totally eliminated bacterial contamination, provided
care was taken not to touch the outer surface of the
cover after examination. The lens covers used were
specially made for the study since they are not industrially
produced. Therefore the development and subsequent
production of lens covers for dermatoscopy is urgently
needed. An alternative may simply to be to apply a
piece of clear plastic saran wrap (cling film) over
the lens head and dispose of this after each examination.
Finally, dermatologists working on dermatoscopes
should guard against any contamination from these
devices and becoming a pathogen vehicle themselves,
a likely occurrence in the absence of precautions.