Susceptibility of HPV16 and 18 to high level disinfectants indicated for semi-critical ultrasound probes

Abstract

Ultrasound probes used in endocavitary procedures have been shown to be contaminated with high-risk HPV after routine use and HPV is also known to be resistant to some high level disinfectants (HLDs). This study compared efficacy of two leading ultrasound probe HLD methods; liquid ortho-phthalaldehyde (Cidex® OPA) and an automated device using sonicated hydrogen peroxide (trophon® EPR) against HPV16 and HPV18 in a hard-surface carrier test. Native HPV16 and HPV18 virions were generated in organotypic epithelial raft cultures. Viral lysates were dried onto carriers with a 5% (v/v) protein soil. Efficacy tests were performed against the automated device at 35% and 31.5% H2 O2 and 0.55% OPA in quadruplicate with matched input, neutralization, and cytotoxicity controls. Hypochlorite was included as a positive control. Infectivity was determined by the abundance (qRT-PCR) of the spliced E1^E4 transcript in infected recipient cells. The automated HLD device showed excellent efficacy against HPV16 and HPV18 (>5 log10 reductions in infectivity) whereas OPA showed minimal efficacy (<0.6 log10 reductions). While HPV is highly resistant to OPA, sonicated hydrogen peroxide offers an effective disinfection solution for ultrasound probes. Disinfection methods that are effective against HPV should be adopted where possible.

Keywords: high level disinfection (HLD); ortho-phthalaldehyde; trophon EPR; virucidal.

Figure 1

Differing efficacy profiles of disinfectants against HPV. HPV16 (A) or HPV18 (B) virions were subjected to hard surface carrier tests based on the ASTM E1053‐11 standard test method against the disinfectants indicated. Virus films were dried onto 50 mm diameter ABS carriers in the presence of a 5% fetal bovine serum soil before being disinfected according to the disinfectant or device manufacturer's instructions. Viral films were assayed for infectivity using a quantitative RT‐PCR based method detecting the spliced E1^E4 transcript in infected recipient cells. Post‐disinfection infectivity was compared to input to determine log₁₀ reductions. Each efficacy test was conducted in quadruplicate and was paired with a matched neutralization control. Data is expressed as an average of n = 4; error bars indicate standard deviation. *=complete inactivation of the virus as shown by a lack of detectable infectivity relative to the uninfected control; OPA, ortho‐phthalaldehyde.