A procedure often used in physical therapy (PT) clinics is therapeutic ultrasound (US). This equipment and associated gel comes in contact with patient skin, possibly acting as a reservoir for bacteria. This study sampled US heads, gel bottle tips and gel from nine outpatient PT clinics in Southeastern Tennessee. Samples were collected using sterile swabs. At the microbiology laboratory, these swabs were used to inoculate mannitol salt agar and CHROM-MRSA agar (for Staphylococcal species) and tryptic soy broth to determine non-specific bacterial contamination. US heads, gel bottle tips and gel had variable levels of contamination. Tips of gel bottles were the most contaminated, with 52.7% positive for non-specific bacterial contamination and 3.6% positive for methicillin-resistant Staphylococcus aureus (MRSA). Contamination of gel by non-specific bacteria was found in 14.5% of bottles sampled. US heads (35.5% of those sampled) had non-specific bacterial contamination, with no MRSA detected. Disinfecting US heads following initial swabbing resulted in removal of 90.9% of non-specific contamination. Gel storage at temperatures below 40 °C was found to encourage the growth of mesophilic bacteria.
This study demonstrated the necessity for better disinfecting and storage protocols for US heads and gel bottles in PT clinics.