A randomised trial investigating the effectiveness and safety of three IVF laboratory disinfectants

Study question The primary aim of this study was to evaluate the efficacy and safety of 70% ethanol (Eth), 6% hydrogen peroxide (HP) and a commercial quaternary ammonium solution (QAC) used as disinfectants in IVF laboratories. Summary answer All three disinfectants were similar in their bactericidal efficacy, but HP had more embryo-toxic characteristics than Eth and the commercial QAC. HP is not therefore recommended for use in the IVF laboratory. What is known already Ethanol has been the most commonly used disinfectant in IVF laboratories. It is cost-effective with a broad effect against bacteria, but it is also a known volatile organic compound (VOC). QACs have been suggested by a commercial study to be harmless to sperm, while HP has also been shown to act as an effective disinfectant both medically and in the home; neither are VOCs and hence believed safe alternatives for the IVF laboratory. Study design, size, duration (1) Difco-Hycheck non-sensitive agar slides were touched on lab surfaces wiped with Eth, HP, QAC or not wiped (control). (2) Two-cell mouse embryos cultured either with; direct contact (1:20 disinfectant to media), residue (culture dish with dried-rinsed disinfectant residue) or incubator-cleaned (media equilibrated in benchtop incubators previously wiped with disinfectants). Participants/materials, setting, methods (1) Bacterial counts scored after 48h incubation, 3 replicates/surface. (2) 176 embryos were randomly distributed to each disinfectant scenario, on 3 treatment days. Embryo development was assessed daily to the blastocysts stage. All embryos were cultured in 40ul drops under oil, 2-10 per drop and one media change at 48h Main results and the role of chance (1) There was no difference in the bactericidal efficacy of the three disinfectants (0, 0 and 0.3 ± 0.3 colonies for HP, QAC and Eth respectively), but all had significantly less colonies than the unwiped control (13 ± 1, P < 0.05). (2) Direct contact: halted embryo growth at the two-cell stage; QAC and HP embryos showed visible signs of degeneration at 4h, whereas ethanol appeared to ‘fix’ the embryos. Residue: all HP and QAC embryos degenerated at the two-cell stage, whereas 44% of embryos exposed to ethanol residue developed to blastocysts (similar to controls, 67%). Incubator-cleaning, HP significantly reduced blastocyst development (3/19, 16%) compared to QAC (21/25, 84%, P < 0.001), and controls, 19/24 (67%, P < 0.01) but not compared to Eth treatment (12/20, 60%). ANOVA and Fishers Exact tests were used. Limitations, reason for caution While clearly demonstrating the toxic effects of disinfectants, it should be noted this trial deliberately studied the worst case scenario. Further trials with variable outgassing times, using benchtop and traditional CO2 incubators would gain a greater insight into cleaning protocols, as VOCs become ‘trapped’ in incubators with low gas turnover. Wider implications of the findings Direct disinfectant contact was lethal in all cases. While Eth did permit some blastocyst development, it is a known embryo-toxic VOC, and thus should only be used if VOC levels can be monitored. The QAC left a toxic residue, but no detrimental effects were observed in recently cleaned incubators. HP proved lethal in all testing scenarios. Understanding disinfectant mechanisms of action allows IVF laboratory staff to use them in the least compromising way to embryos. Study funding/competing interest(s) This study was funded from in-house budgets and the authors have no conflicting or competing interests to declare. Trial registration number N/A