Historically, care for patients with high-consequence infectious diseases (HCIDs) has been limited to biocontainment units (BCUs) that managed the challenges of providing complex clinical care, including waste handling. ^{Reference Kraft, Hewlett and Koepsell1} However, recent cases of viral hemorrhagic fevers (VHF) and the global mpox outbreak (in which clade identification was delayed) ² underscore the importance of healthcare facilities beyond traditional BCUs being prepared to handle category A waste.

Guidelines surrounding category A waste handling require it to be inactivated on site via incineration or autoclave inactivation or transported to an off-site facility that can perform inactivation compliant with federal regulations. ³ Sites for waste incineration are rare, and transport of untreated infectious waste is expensive and logistically challenging, given potential volumes of patient waste. ^4,5 For example, the most critical patient with Ebola virus disease at Emory University Hospital generated 1,312 bags of waste needing disposal (personal communication). As a result, many regional treatment facilities for HCIDs have chosen to inactivate waste on site using an autoclave. ^{Reference Lowe, Gibbs, Schwedhelm, Nguyen and Smith6}

Guidance for pathogen inactivation suggests that a goal temperature of 121°C be maintained for 30 minutes, ⁴ and Flinn et al ^{Reference Flinn, Michalek, Bow, Hynes, Philpot and Garibaldi7} described the need for site-specific validation for different waste types, including goal sterilization temperatures. Centers with BCUs have previously described methods for autoclaving category A waste and noted challenges with protocol validation, including (1) 1–2 biological indicators placed within sealed bags sometimes did not pass; (2) BIs placed within solidifier used to stabilize liquid waste did not pass; and (3) different cycle types, temperatures, and durations were necessary to achieve kill depending on the consistency and volume of waste. ^{Reference Flinn, Michalek, Bow, Hynes, Philpot and Garibaldi7,Reference Garibaldi and Chertow8} Due to these challenges, a prior validation study led to recommendations for using different cycle types for dry waste, damp linen, and liquid waste, avoiding the use of solidifiers, and opening bags prior to placing them in the autoclave. ⁹ Although these modifications inactivated biological indicators, opening waste bags presents a potential for contamination to staff and the environment, and the solidifier is useful for safe movement of liquid waste. To maximize safety to personnel, we explored the validation of autoclave parameters that ensure inactivation of all waste types while maintaining bag closure.

Results

Successful cycle parameters were identified for each waste type, with kill of all BIs present within the load on 3 successful cycles (Table 1). For linen, the cycle time increased from baseline after the data loggers revealed disparities in target temperature acquisition depending on the presence and amount of moisture added to the linens (Fig. 1A). The liquid waste with solidifier demonstrated a delayed rise in temperature, particularly liquids within a container rather than a biohazard bag (Fig. 1B). Although the autoclave itself reached and maintained a sterilization temperature of 132°C, loads run using a data logger demonstrated that the liquids took longer to reach an acceptable minimal temperature (121°C) and were maintained at that temperature for a shorter true sterilization time. It took 9 attempts to identify final parameters for liquids, modifying the number of vacuum pulses, steam charge, and sterilization time. Laboratory or sharps waste similarly required 9 total loads to achieve three successful biological indicator inactivations, with the sterilization time doubled to 60 minutes.

Table 1. Optimized Cycle Parameters by Waste Type

Note. Hg, millimeters mercury; PSIG, pounds per square gauge.

Figure 1. (A) Linen cycle temperature comparison. (B) Solidified liquid waste temperature comparison.

Visual inspection of the bags at the conclusion of the cycles confirmed that they all either ruptured or their tape closures had released during the cycle. The position of the bags on the rack, the position of the inner closure relative to the outer closure, and the tape used did not impede the opening of the bags during the cycle.