Comparison of Floor Cleaning and Disinfection Processes in a Research Animal Facility

Floor cleaning and disinfection are essential components of maintaining animal health status and meeting regulatory requirements in research vivaria. However, best practices for method, frequency, and evaluation techniques have not been established. Reuse of cotton string mop and bucket systems has been implicated in spreading contamination in the human hospital setting. We evaluated 4 different combinations of disinfectant and mop systems commonly used in rodent vivaria. Eight housing rooms were mopped a total of 4 times using one of the following methods: quaternary ammonium compound (QUAT) and cotton string mop (QC), QUAT and microfiber mop (QM), hydrogen peroxide disinfectant (HPD) and cotton string mop (HC), or HPD and microfiber mop (HM). ATP and RODAC samples of the floor were taken before and after mopping. The time to mop each room, floor drying time, and the amount of disinfectant used were recorded. The QC method was associated with significantly more bacterial contamination while all other methods significantly reduced bacterial contamination. The QC method performed significantly worse in reducing bacterial contamination as compared with all other methods when cotton mop heads were reused. All methods except QC significantly reduced ATP levels, with the HC and HM methods being significantly more effective at reducing ATP levels than the QC and QM methods. Costs were similar for the QC, QM, and HM methods. The results of this study indicate that reuse of cotton string mop heads with QUAT increases floor contamination while HPD is effective for up to 3 reuses. Single use microfiber mops were effective with both QUAT and HPD but did not result in more effective cleaning or disinfection than cotton string mops.

Validation of Sanitization Practices in Single-use Individually Ventilated Mouse Cages at Standard and Thermoneutral Temperatures

Vivarium husbandry practices are based on performance data and adhere to applicable regulatory guidelines. Refinements in husbandry and optimization of sanitization protocols improve animal wellbeing and help standardize the microenvironment, contributing to research reproducibility. The objective of this study was to evaluate the microenvironment to establish performance standards for mouse husbandry and sanitization, including housing at standard and thermoneutral temperatures. Male C57BL/6J mice were housed singly and in groups in disposable IVCs on α-cellulose or corncob bedding and microenvironmental indicators (ammonia, carbon dioxide) were evaluated. In addition, microbial bioburden tests (ATP and RODAC) were performed on cages and cage accessories on days 0, 7, 14 and, 28 to 30 after cage change. Water testing and aerobic culture of the waterspout of bottles containing chlorinated water were performed to determine acceptable replacement schedules. Ammonia levels remained below the National Institute of Occupational Safety and Health 8-h recommended exposure limit for humans (25 ppm) at all time points for all housing conditions through day 21 for group-housed mice, and through day 30 for singly housed mice. Microbial bioburden results for cage accessories and water testing were acceptable up to 28 d after cage change (RODAC less than 50 CFU; ATP less than 100,000 RLU) at both standard and thermoneutral housing temperatures. Mice remained clinically healthy throughout the studies. These results support site operating practices and verify extended sanitization recommendations per the Guide of the Care and Use of Laboratory Animals in this disposable IVC environment: group-housed mice receive bottom cage and water bottle change up to every 14 d with full cage change (including lid and accessories) every 28 d, and singly housed mice receive full cage change every 28 to 30 d or sooner.

Extending the Use of Disposable Caging Based on Results of Microbiologic Surface Testing

Prions are proteinaceous infectious agents that are highly resistant to denaturation. Sterilization of prion-contaminated mouse cages requires chemical agents and increased autoclave temperatures that damage traditional cages, thus increasing facility costs. Disposable cages are a possible alternative that might decrease replacement costs without compromising the environment of the mice. We compared our standard protocol of changing traditional cages and bedding once every 2 wk to an experimental protocol using disposable cages in which only the bedding was changed once every 2 wk over an 8-wk period. We hypothesized that disposable cages would retain an acceptable level of cleanliness (measured by ATP swabs and contact plates) for at least 8 wk when bedding is replaced every 14 d. Results from ATP swabs and contact plates showed no difference between the 2 protocols during the 8-wk experiment. Prolonged use (that is, as long as 8 wk) of disposable cages had no additional environmental concerns, compared with traditional cages.

Evaluation of 5 cleaning and disinfection methods for nets used to collect zebrafish (Danio rerio)

Few standardized methods of cleaning and disinfecting equipment in zebrafish facilities have been published, even though the effectiveness of these procedures is vital to preventing the transmission of pathogenic organisms. Four chemical disinfectants and rinsing with municipal tap water were evaluated for their ability to disinfect nets used to capture zebrafish. The disinfectants included benzalkonium chloride+methylene blue, sodium hypochlorite, chlorine dioxide, and potassium peroxymonosulfate+sodium chloride for a soak time of 5 or 30 min. Disinfection effectiveness was evaluated by using an ATP-based system that measured the reduction in absolute number and percentage of relative light units. In addition, nets were cultured aerobically on blood and MacConkey agar plates to determine the number of bacteria remaining after disinfection procedures. Soaking nets in sodium hypochlorite for 30 min and in potassium peroxymonosulfate+sodium chloride for 5 or 30 min were effective means of disinfection, according to at least 90% reduction in the number of relative light units and no bacterial growth after cleaning. These results will aid facility managers, veterinarians and investigators in selecting net cleaning and disinfection protocols.

Efficacy and limitations of an ATP-based monitoring system

Monitoring of sanitation is an essential function of laboratory animal facilities. The purpose of the current study was to assess the ability of an ATP-based system to detect microbes and organic contaminants. Serial dilutions of Escherichia coli, Staphylococcus aureus, Toxocara canis eggs, Toxoplasma gondii tachyzoites, epithelial cells, and rodent blood, urine, and feces were analyzed according to the manufacturer's recommendations. The limit of E. coli detection was 10(4) organisms; sonication of E. coli significantly improved detection, indicating incomplete bacterial lysis in the detection system. Detection of S. aureus was significantly greater than that of E. coli with a limit of detection of 10(2); sonication did not alter results. In contrast, detection of T. canis, T. gondii, RBC, and epithelial cells was robust and ranged from 2 T. canis eggs to 10 epithelial cells. Urine was weakly detected, with a limit of detection at 1:10 dilution. Detection of all cell types except epithelia had a strong linear correlation to total cell number. In addition, our data demonstrate that the efficacy of the detection system can be affected adversely by residual disinfectants and that sample-bearing swabs are stable for more than 7 h after swabbing. These data demonstrate that this ATP based system sensitively detects pure cells and organic contaminants with a strong degree of linear predictability. A limitation of the system is its inability to detect gram-negative bacteria efficiently because of incomplete cell lysis.

Quantification, distribution, and possible source of bacterial biofilm in mouse automated watering systems

The use of automated watering systems for providing drinking water to rodents has become commonplace in the research setting. Little is known regarding bacterial biofilm growth within the water piping attached to the racks (manifolds). The purposes of this project were to determine whether the mouse oral flora contributed to the aerobic bacterial component of the rack biofilm, quantify bacterial growth in rack manifolds over 6 mo, assess our rack sanitation practices, and quantify bacterial biofilm development within sections of the manifold. By using standard methods of bacterial identification, the aerobic oral flora of 8 strains and stocks of mice were determined on their arrival at our animal facility. Ten rack manifolds were sampled before, during, and after sanitation and monthly for 6 mo. Manifolds were evaluated for aerobic bacterial growth by culture on R2A and trypticase soy agar, in addition to bacterial ATP quantification by bioluminescence. In addition, 6 racks were sampled at 32 accessible sites for evaluation of biofilm distribution within the watering manifold. The identified aerobic bacteria in the oral flora were inconsistent with the bacteria from the manifold, suggesting that the mice do not contribute to the biofilm bacteria. Bacterial growth in manifolds increased while they were in service, with exponential growth of the biofilm from months 3 to 6 and a significant decrease after sanitization. Bacterial biofilm distribution was not significantly different across location quartiles of the rack manifold, but bacterial levels differed between the shelf pipe and connecting elbow pipes.