Microbial contamination of immersion biometry ultrasound equipment

To investigate the prevalence of microorganisms on ultrasound biometry equipment and cleaning habits.

Observational case series.

Thirty-four university-based and private ophthalmology clinics.

In a prospective multicenter study, clinics representative of every region of the country sampled their fixed immersion biometry equipment (i.e., ultrasound probe, immersion shell, and infusion tubing) for bacteria and fungi. Assessment of the cleaning habits for this equipment was conducted by way of a standard questionnaire that included type of fluid and delivery method, frequency of fluid change, method of cleaning the probe and shell, and frequency of tubing change and/or cleaning.

Frequency (prevalence), descriptive statistics, and type of microorganisms.

Eighteen samples (53% [18/34]) grew organisms from either the probe/shell or tubing. Positive cultures were found in 32% (11/34) of the immersion shell/probes and in 31% (10/32) of the infusion tubing samples. The bacteria most commonly cultured from both probe/shell and tubing was coagulase-negative Staphylococcus, whereas Penicillium species was the most commonly cultured fungus (exclusively from the probe/shell). Overall, fungi (Penicillium and Alternaria species) were cultured in 12% of the probe/shell samples. Only 14% of the study sites adequately disinfected the probe/shell according to Centers for Disease Control and Prevention (CDC) guidelines, which recommend a 5-minute soak in antiseptic.

The bacteria and fungi that colonize biometry equipment are not being adequately eliminated by the cleaning/disinfecting techniques employed in most ophthalmology clinics. These results also may apply to contact biometry, pachymetry, and tonometry equipment as well. Clinicians should follow the CDC recommendations for disinfecting instruments that come in contact with the eye, and the infusion tubing should be changed after each patient.