ESTABLISHMENT OF AN IN-USE TESTING METHOD FOR EVALUATING DISINFECTIONOF SURGICAL-INSTRUMENTS USING THE DUCK HEPATITIS-B MODEL

Nosocomial transmission of hepatitis B virus (HBV), associated with in terventional procedures, has been attributed to its survival on improp erly decontaminated instruments. To date, guidelines for chemical dis infection of potentially contaminated heat-sensitive instruments have been based largely on extrapolation of data from in-vitro disinfectant testing. Direct infectivity testing has not been possible for HBV bec ause of the lack of a practical culture assay or susceptible experimen tal animal model. In this study the related duck hepadnavirus was used to simulate in-vivo transmission of a HBV during surgery, and to eval uate the effectiveness of 2% glutaraldehyde disinfection of surgical l aparoscopes. Multiple laparoscopic liver biopsies were performed on 'b iohazardous' duck hepatitis B (DHBV) positive ducks. Laparoscopes were then subjected to different disinfection regimes using 2% glutaraldeh yde, and residual infectivity tested by placing their tips into the pe ritoneal cavities of uninfected four-day-old ducklings. Direct transmi ssion of DHBV occurred in all ducks when laparoscopes were not washed. Rinsing with water lowered the transmission rate to 64% and no infect ion transmission occurred after 5 min of contact time with the disinfe ctant. In contrast, previous in-vitro studies had shown complete viral inactivation after a shorter period of disinfection. It is postulated that the longer inactivation time observed in our study may be a resu lt of surface interactions of virus and instrument, interfering with d isinfectant access or activity. Tests of instrument surface samples fo r viral DNA by the polymerase chain reaction (PCR) did not correlate w ith transmission of virus infection in vivo. PCR is an inappropriate t est for evaluating the efficacy of disinfectant action despite its sen sitivity. This in use method will allow testing of other decontaminati on procedures and their effectiveness on more complex surgical instrum ents.