Assessment of Microbial Reduction by Cage Washing and Thermal Disinfection using Quantitative Biologic Indicators for Spores, Viruses and Vegetative Bacteria

Cage washing is a key process of the biosecurity program in rodent facilities. For the current study, we developed systems (i. e., magnet attachments, quantitative biologic indicators (Q-BI), and measurement of thermal disinfection at equipment level) to assess the microbial decontamination achieved by a rodent equipment washer with and without thermal disinfection. 99% of the magnets remained in position to hold Q-BI and temperature probes inside cages, water bottles or at equipment level across a cabinet washer chamber with loads dedicated to either housing or drinking devices. Various types of Q-BI for Bacillus atrophaeus, Enterococcus hirae and minute virus of mice were tested. To simulate potential interference from biologic material and animal waste during cage processing, Q-BI contained test soil: bovine serum albumin with or without feces. As a quantitative indicator of microbial decontamination, the reduction factor was calculated by comparing microbial load of processed Q-BI with unprocessed controls. We detected variation between Q-BI types and assessed the washer's ability to reduce microbial load on equipment. Reduction factor results were consistent with the Q-BI type and showed that the washing and thermal disinfection cycle could reduce loads of vegetative bacteria, virus and spore by 5 log10 CFU/TCID50 and beyond. Thermal disinfection was monitored with temperature probes linked to data loggers recording live. We measured the period of exposure to temperatures above 82.2 °C, to calculate A0, the theoretical indicator for microbial lethality by thermal disinfection, and to assess whether the cabinet washer could pass the minimum quality standard of A0 = 600. Temperature curves showed an A0 > 1000 consistently across all processed equipment during thermal disinfection. These data suggest that, when sterilization is not required, a cabinet washer with thermal disinfection could replace an autoclave and reduce environmental and financial waste.

Effective disinfecting of protective devices used in the course of treating SARS-CoV2–positive patients

Background: Powered Air-Purifying Respirator (PAPR) was widely used in Sengkang General Hospital (SKH) during the SARS-CoV-2 outbreak. Ensuring a sustained supply of clean and reusable PAPR masks for frontline medical team is an immediate challenge. The Central Sterile Supplies Unit (CSSU) adopts existing disinfection methods and technology for the reprocessing of reusable personal protective equipment (PPE) such as PAPR masks and goggles. Objective: To determine an effective disinfecting method for protective devices used in the course of treating SARS-CoV2–positive patients. Method: A comparison on surface disinfection and modified thermal disinfection outcome was conducted on 30 PAPR masks through detecting the presence of adenosine triphosphate (ATP) by swab following both disinfecting methods. Results: The modified thermal cycles emerged as the recommended disinfection method. Discussion: The outcome of this study has enhanced understanding on the risk imposed on frontline healthcare personnel who perform surface disinfecting on masks for reuse during the work shift. Leveraging on the current expertise from existing instrument logistics, CSSU takes charge of the processing and stock management of SKH’s PAPR masks. An additional workflow is needed to establish reprocessing methods for other reusable PPEs such as face shields or overalls.

Thermal Disinfection Validation: The Relationship Between A0 and Microbial Reduction

Validating a thermal disinfection process for the processing of medical devices using moist heat via direct temperature monitoring is a conservative approach and has been established as the A0 method. Traditional use of disinfection challenge microorganisms and testing techniques, although widely used and applicable for chemical disinfection studies, do not provide as robust a challenge for testing the efficacy of a thermal disinfection process. Considerable research has been established in the literature to demonstrate the relationship between the thermal resistance of microorganisms to inactivation and the A0 method formula. The A0 method, therefore, should be used as the preferred method for validating a thermal disinfection process using moist heat.

Implementation of a Low-Cost Method to Reduce Bacterial Load in Patient-Room Sink Drains

Background: Sink drains can act as breeding grounds for multidrug-resistant (MDR) bacteria, leading to outbreaks. Drains provide a protected humid environment where nutrient-rich substances are available. Recent and growing installation of water and energy conservation devices have led to increased frequency of drain blockage due to biofilm accumulation. Ineffective drainage may lead to backflow and accumulation of water in the sink during use, increasing the risk of contaminated aerosols formation or direct contamination of surrounding material and equipment. Cleaning and disinfection procedures of sink drains need to be improved to prevent amplification and dispersion of MDR bacteria. The objective of this study was to investigate alternatives to reduce the biofilm and risk of contamination through aerosols. Methods: Sink drains from patient rooms were randomly selected in the neonatal intensive care unit of a 450-bed pediatric hospital. We tested 4 approaches: (1) new drain; (2) self-disinfecting heating-vibration drain; (3) chemical disinfection with 20 ppm chlorine for 30 minutes; and (4) thermal disinfection with > 90°C water for 30 minutes. A special device was used during disinfection to increase the disinfectant contact time with the biofilm. Treatments were conducted weekly, with prior sampling of drain water. Other drains were also sampled weekly, including a control drain with no intervention. Bacterial loads were evaluated using flow cytometry and heterotrophic plate counts. The drains were made of stainless steel, a heat-conductive material. Results: Preliminary results show that chlorine disinfection had a small impact (<1 log) on culturable bacteria at 48 hours after disinfection but not after a week or repeated weekly disinfection. Thermal disinfection using boiling water is promising, showing an important decrease of 4 log in culturable cells after 48 hours and a concentration still 100× lower 1 week after the disinfection. Repeated weekly thermal disinfection maintained lower culturable levels in the drain. No culturable cells were detected in water from the self-disinfecting drain 2 months after installation, whereas the new drain became fully colonized to concentrations similar to those of drains prior to interventions during the same period. Conclusions: Thermal disinfection of drains is a promising alternative to chlorine. This solution is interesting because it is nontoxic and easy to perform, requiring a small volume of hot water. The rapid recolonization of the new drain suggests that replacing contaminated drains is not a sustainable solution and would need to be paired with a thermal disinfection program to maintain low culturable cells.Funding: NoDisclosures: None