Download abstract id: iria 1175

ABSTRACT ID: IRIA 1175
Ultrasound gel is a potential mode of
infection transmission in postoperative
patients. A prospective study.
AIM
Ultrasound is one of the equipments that
are known to transmit nosocomial
infections. The study was conducted to
identify the incidence of infection in post
operative patients following ultrasound
study and the significance of disinfection
methods.
INTRODUCTION
• Ultrasonography(USG) is a commonly used imaging technique in
modern medicine. It is a preferred imaging method, as it is noninvasive, non-ionizing as well as portable [1].
• A gel is used as a coupling media during ultrasound to displace the air
and allow the ultrasound waves to enter the body.
• The gel is an inert material containing carbamer, Ethelene diamine
tetra acetic acid, propylene glycol, trolamine and distilled water.
Coupling gel and the probes have been traced to be a source of
infection [2,3,4,5,6,7].
• Hence, the specialty of Diagnostic Radiology is not an exception and is
a source of nosocomial infection [8].
• With the increase in the number of post operative
and immunocompromised patients being scanned,
effective guidelines for prevention of infection and
disinfection are necessary [9].
• Literature shows limited studies regarding infection in
post operative patients following ultrasound [6,7].
• A number of organisms such as Staphylococcus
aureus, Staphylococcus epidermidis and
Enterococcus faecalis, Klebsiella, Stentrophomonas
maltophilia and Acinetobacter baumannii have been
isolated from the gel[9].
• Hence, every precaution for prevent of infection
transmission should be taken.
• This study highlights the organisms that might
contaminate the gel and ultrasound equipments and
the incidence of infection following ultrasound study
in post operative patients.
• Despite the publishing of many articles regarding
infection, the response from various international
governments is lukewarm.
• International guidelines for disinfection of probes are
available but not for disinfection of gel [5,9].
• Certain governments such as the Canadian
government issued guidelines to be followed at
ultrasound units [10].
Materials & Methods
• This prospective study was conducted in our ultrasound department
and included operated patients in the month of march 2014 over a
period of 30 days.
• 65 patients were included in the study and the same number of
controls were examined. Ethical committee and patient’s consent
were obtained.
• The study included patients who have under gone abdominal and
breast surgeries as these are the patients who might require an USG
following surgery.
• Patients who underwent any neurosurgery as well as laparoscopic
surgery were excluded as the requirement in neurosurgery is almost
nil and in case of laparoscopic surgery, the surgical incision is very
small and does not require direct contact of the transducer with the
scar site. Patients with wound gapping were also included in the
study.
• The patients underwent sonogram on the third postoperative day.
Two transducers (curvilinear and linear) were used for the
sonography study.
• First culture swab was taken from the scar site before the ultrasound
from each patient. After the ultrasound the wound was dressed with
gauze without any antiseptics and the probe was cleaned with a
gauze piece.
• A second culture swab was taken from the scar after 48hours
following the first swab. So a total of two culture swabs were taken
from each patients.
• Swabs were taken from the transducers and ultrasound gel at the
beginning of the study, at the middle of the study and at the end of
the study.
• Hence, a total of 139 swabs were taken(130 swabs from 65 patients
and 9 swabs from the transducer and gel).
• The collected samples were inoculated in 5% sheep blood agar (M1
YYA), Mac Conkey agar (Mo8Za) and Saborauds dextrose agar
(M0167). Antimicrobial susceptibility testing, was carried out for the
isolated organisms, on Mueller – Hinton agar (M173), by using the
Kirby-Baver disc diffusion method. The samples were read at 24 and
48hrs after inoculation.
Mueller-Hinton agar
SHEEP BLOOD AGAR
Mac CONKEY AGAR
RESULTS
• The initial swabs from the gel bottle and probes showed heavy
contamination with Klebsella pneumoniae and Acinetobactor, both
resistant to Amoxicillin / Clavulanic acid.
• High incidence of Escherichia coli infection was noted in first sample
on the 3rd post operative day (16.9%)(Table 1)
TABLE 1
E.coli
Frequency
11
Percent
16.9
Cumulative
Percent
16.9
Ps. aeruginosa
2
3.1
20.0
Staph aureus
7
10.8
30.8
Ps. aeruginosa + Staph.
aureus
1
1.5
32.3
E.coli + Klebsiella
1
1.5
33.8
No growth
43
66.2
100.0
Total
65
100.0
Organism
Table-1: First sample taken at the postoperative site on 3rd postoperative day.
An increase of 4.7% in infection rate was noted in the second
sample at 48hours after ultrasound (p=0.0001) [table 2 & 3].
E. coli
Frequency
9
Percent
13.8
Cumulative
Percent
13.8
Ps. aeruginosa
2
3.1
16.9
Staph. aureus
7
10.8
27.7
Klebsiella
4
6.2
33.8
E coli + Klebsiella
2
3.1
36.9
Ps. aeruginosa +
Staph.aureus
1
1.5
38.5
No growth
40
61.5
100.0
Total
65
Organism
100.0
Table -2: Second sample taken after ultrasound
Frequency
E.coli
Ps.aeruginosa
Staph. Aureus
Klebsiella
E.coli+klebsiella
• Klebsiella was isolated in 4 patients while one patient had Escherichia
coli and Klebsiella following ultrasound with an increase in overall
infection rate following ultrasound (p<0.0001) [table 2&3]. No patient
had growth of Acinetobactar. The culture of the gel from the bottle at
the end of the study showed persistence of Klebsiella colony.
TABLE 3
sample 1
E. coli
Ps.
aeruginosa
Staph. aureus
Ps. auriginosa
+
staph.aureus
E.coli+
Klebsiella
No growth
Total
Sample 2
Ps.
Escherich Psuedomon
aerugin Staph. Klebsiel ia coli + as +Staph.
No
E. coli osa aureus
Klebsiella aureus
la
growth Total
9
0
0
1
1
0
0
11
0
2
0
0
0
0
0
2
0
0
7
0
0
0
0
7
0
0
0
0
0
1
0
1
0
0
0
0
1
0
0
1
0
0
0
3
0
0
40
43
9
2
7
4
2
1
40
65
Table-3: # P =0.000. E. coli- Escherichia coli; Staph. aureus- Staphylococcus aureus;
Ps.aeruginosa-Pseudomonas aeruginosa
Pearson
chisquare
value
2.840#
DISCUSSION
• An infection acquired within 48 hours after the admission of the patient in the
hospital is known as nosocomial infection [11].
• Poor surgical asepsis, type of wound, Poor socio Economic status, over crowded
hospitals, lack of guidelines, unawareness among health workers, increasing
number of immunocompromised patients are some of the factors increasing the
risk of developing nosocomial infections [12].
(Global patient safety challenge 2005-2006, www.who.int/patientsafety)
• Gel and the probe has been proved to be a source of infection by various studies
[2,4,5,6,7,13,14].
• The coupling gel is commonly used in radiology, cardiology and physiotherapy
[3,5].
• As patients with open wound or fresh scar are at high risk of infection, necessary
precaution is to be followed to reduce the risk of nosocomial infection.
• Sykes et al have reported a high level (64.5%) of contamination in ultrasound
equipment's [15].
• Prospective studies have reported the bacterial colonisation in the
transducer, the property of the gel to harbour bacteria and the methods of
cleaning the probe[5,16].
• Infection transmission from the gel has been reported by Hutchinson et al
and Spencer et al but no reported gel contamination with klebsiella [2,12].
• Outbreaks following ultrasound, both after diagnostic as well as intervention
has been reported as cross infection [6,12,17,18].
• The gel supports bacterial contamination and has no bactericidal agent [18].
• An increase in incidence of infection by 4.7% following ultrasound in our
study is statistically significant(p<0.0001) and the presence of Klebseilla in 5
patients following ultrasound clearly indicates that the source of infection is
the gel since, the probe was cleaned after every ultrasound.
• The contamination of gel at the manufacturing unit as in our case should be
avoided by following aseptic precautions.
• Fumigation of the room does not eliminate the bacteria from either the gel
bottle or from the larger gel container. Addition of bactericidal agents to the
gel can help prevent nosocomial infection.
• As the gel is used for ECG leads, it may contribute to infection in
cardiothoracic intensive care units. Use of sterile pack will prevent infection
transmission.
• Outbreak of infection following prostate biopsy has proved the importance
of use of sterile gel as well as probe covers during intervention [18].
• As the cost of a sterile gel pack is high, its use has not gained popularity
among radiologists and sonologists in India. But it’s use has to be insisted in
ICU and post operative patients.
• We agree with muradali et al and Hutchinson et al that single wipe of the
probe does significantly reduce the bacterial contamination [2,5].
• But, it does not elimnate the bacteria in the gel. Reduction of bacteria by
45% has been reported by single wipe technique, which is adequate for a
routine Ultrasound clinics [9].
• Double cleaning methods with use of cloth and disinfectant is better than
the single cloth wipe [13,14]
• As our study shows a significant increase(p=0.0001) in infection, it is
recommended all probes be cleaned by any of the methods at the
end of the day [5,18,19].
• Most cost effective method is by cleaning with 0.05% chlorhexidine at
the end of the day [5].
• Soap and water, 70% alcohol and chlorine can be used for vaginal
probes sterilization [19].
• Safety instructions and guidelines has to be followed as
recommended [4,10].
• Probe vendors should provide instructions for cleaning the probe.
Ultraviolet light can be used for cleaning probe in operation theatres
with a microbial reduction of 100% [20].
• As probe covers and sterile gels are used, the incidence will be less
when compared to ultrasound done at the wards.
• In conclusion, ultrasound gel permits bacterial growth and is a
significant source of infection in postoperative patients. Use of sterile
gel is recommended in post operative patients along with probe
sterilisation to prevent increase of nosocomial infection.
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