Virucidal Efficacy of Household Dishwashers

Not only since SARS-CoV-2, have transmission routes of viruses been of interest. Noroviruses e.g., can be transmitted via smear infection, are relatively stable in the environment and very resistant to chemical disinfection. Some studies determined the virucidal efficacy of laundering processes, but few studies focused on the virucidal efficacy of dishwashing processes. Here, especially consumer related conditions are of interest. Households for example are a hotspot of norovirus infection and thus a sufficient reduction of these and other viruses from dishes must be insured to avoid an infection via this route. The likelihood of such an event should not be underestimated, since it was shown that the washing machine can be a reservoir for the transmission of extended spectrum beta-lactamase producing bacteria in newborns. Although viruses do not replicate in these devices a transmission via contaminated cutlery e.g., cannot be excluded. Using a consumer related approach to determine the virucidal efficacy of dishwashers, we found a combination of a bleach containing dishwasher detergent, a cleaning temperature of 45 °C for 45 min and a rinsing temperature of 50 °C, to be sufficient to reduces viral titer of bovine corona virus, murine norovirus and modified vaccinia virus by 4.8, 4.2 and 3.8 logarithmic stages respectively

Cultivation-Based Quantification and Identification of Bacteria at Two Hygienic Key Sides of Domestic Washing Machines

Detergent drawer and door seal represent important sites for microbial life in domestic washing machines. Interestingly, quantitative data on the microbial contamination of these sites is scarce. Here, 10 domestic washing machines were swab-sampled for subsequent bacterial cultivation at four different sampling sites: detergent drawer and detergent drawer chamber, as well as the top and bottom part of the rubber door seal. The average bacterial load over all washing machines and sites was 2.1 ± 1.0 × 104 CFU cm−2 (average number of colony forming units ± standard error of the mean (SEM)). The top part of the door seal showed the lowest contamination (11.1 ± 9.2 × 101 CFU cm−2), probably due to less humidity. Out of 212 isolates, 178 (84%) were identified on the genus level, and 118 (56%) on the species level using matrix-assisted laser desorption/ionization (MALDI) Biotyping, resulting in 29 genera and 40 identified species across all machines. The predominant bacterial genera were Staphylococcus and Micrococcus, which were found at all sites. 22 out of 40 species were classified as opportunistic pathogens, emphasizing the need for regular cleaning of the investigated sites

Metatranscriptomic Analysis of Bacterial Communities on Laundered Textiles: A Pilot Case Study

Microbially contaminated washing machines and mild laundering conditions facilitate the survival and growth of microorganisms on laundry, promoting undesired side effects such as malodor formation. Clearly, a deeper understanding of the functionality and hygienic relevance of the laundry microbiota necessitates the analysis of the microbial gene expression on textiles after washing, which—to the best of our knowledge—has not been performed before. In this pilot case study, we used single-end RNA sequencing to generate de novo transcriptomes of the bacterial communities remaining on polyester and cotton fabrics washed in a domestic washing machine in mild conditions and subsequently incubated under moist conditions for 72 h. Two common de novo transcriptome assemblers were used. The final assemblies included 22,321 Trinity isoforms and 12,600 Spades isoforms. A large part of these isoforms could be assigned to the SwissProt database, and was further categorized into “molecular function”, “biological process” and “cellular component” using Gene Ontology (GO) terms. In addition, differential gene expression was used to show the difference in the pairwise comparison of the two tissue types. When comparing the assemblies generated with the two assemblers, the annotation results were relatively similar. However, there were clear differences between the de novo assemblies regarding differential gene expression