ULTRASOUND SCAN

COUPLING GEL AS A POTENTIAL SOURCE OF INFECTION.

Abstract

O b j e c t i v e : To assess the infective potential of ultrasound gel and probes when used in a routine manner on ambulatory
patients with intact skin. At our institute, ultrasound probes are wiped with a non-sterile absorbent paper towel after each patient. The probes
become dry and clean in social terms but we were unsure if they also became bacteriologically decontaminated after wiping clean. We also
wished to ascertain the intrinsic infective potential of ultrasound gel. Materials a n d m e t h o d s : Bacteriological samples were taken from probe
surface (after wiping it clean as per our protocol); gel dispensing bottles; and the gel jars that contain the gel in bulk. A total of 61 samples
were cultured, out of these 13 were jar samples that were acquired daily on 13 days, 10 from gel bottles and 38 from probe surface (27
before beginning ultrasound, 11 after ending the day's work). Probe surface samples were collected on sterile cotton wipes dipped in sterile
nutrient broth; bottle and jar samples were collected by sterile nickel loops and cultured on commercially available nutrient agar. Colonies
were counted at 24 and 48 hours. R e s u l t s : The results show bacterial contamination in all (10/10) gel bottle samples, 7% pre-scan probe
surface wipes (2/27) and 27.3% (3/11) on post scan wipes. Gel Jar samples were sterile on the first 3 days and then progressively showed
greater colony counts. This showed that the gel is initially sterile but is apparently contaminated from air and it serves as growth medium
for bacteria. C o n c l u s i o n : We conclude that the highest contamination is observed in gel bottle samples (100%). The lowest contamination
was observed from wiped probe samples. This was probably due to repeated cleaning of probes by the operators. Gel jar samples have
the second highest contamination but the initial samples showed no growth. The ultrasound gels probably contain no or little antibacterial
agent and the gel serves as a growth medium for bacteria.