These household appliances are often infested with resistant bacteria

How big is the germ load in washing machines and dishwashers?

Often lurk in your own household dangerous germs. For example, sponges and wipers that are used over an extended period of time can form veritable sprouting germs. In a recent study at the Faculty of Life Sciences at Rhein-Waal University of Applied Sciences, washing machines and dishwashers from private households were examined for antibiotic-resistant germs.

Although germs from washing machines and dishwashers are not an immediate health hazard, "one must also do something about it", according to the announcement of Rhein-Waal University of Applied Sciences. In cooperation with the medical care center Stein and colleagues from Mönchengladbach, scientists at the Faculty of Life Sciences at Rhein-Waal University of Applied Sciences have tested household appliances for antibiotic-resistant germs. According to the researchers, a risk can arise, for example, if only low-temperature programs are used.

No MRSA colonization detected

According to the scientists, in addition to methicillin-resistant Staphylococcus aureus strains (MRSA) also so-called beta-lactamases (enzymes formed by bacteria) were the focus of the investigation. These enzymes present a problem because they can destroy and render ineffective various antibiotics such as penicillins or carbapenems. Fortunately, according to the researchers in the washing machines and dishwashers no MRSA were detectable. However, in the home appliances more often than expected settlements were found with beta-lactamase-forming microorganisms.

Beta-lactamases in a majority of household appliances

Of the populations of beta-lactamases, about 96 percent of dishwashers were affected, and 79 percent of the appliances studied were washing machines, according to the researchers. To what extent the washing processes affect the resistant germs, the scientists examined in a further step, in which they gave cotton test fabric samples with non-resistant and resistant strains of bacteria in the devices. These were washed in washes both with and without activated oxygen bleach and at temperatures between 20 and 50 degrees Celsius.

At higher temperatures almost all germs are killed

The evaluation of the test washes showed that at higher temperatures, the contamination by the germs was eliminated to almost 100 percent - both in the resistant pathogens as well as in the ordinary germs. In general, however, the reduction in the resistant bacteria was slightly lower, the researchers report. "Antibiotic-resistant bacteria can withstand the usual washing conditions better than non-resistant strains, but higher temperatures and the use of detergents with oxygen bleach can safely remove even these germs," ​​said Professor. Dirk Bockmühl, Professor of Hygiene and Microbiology at Rhein-Waal University of Applied Sciences and head of the study.

At least 40 degrees Celsius advised

Although "the results in no way suggest a direct health risk from household appliances, it makes sense to regularly clean washing machines and dishwashers and not only to use low-temperature programs," emphasizes Professor Bockmühl. Especially in households with infants or relatives in need of care, it is also recommended to regularly use washing programs of at least 40 degrees Celsius in combination with powdered or pearl-shaped heavy-duty detergents in the washing machine.

Dishwashers from a hygiene point of view the best choice

According to the researchers, almost all programs used in dishwashers offer safe protection against germs. Especially when hygienically critical foods such as raw meat were prepared, the dishwasher was the best choice for crockery and cutlery, which came into contact with these foods, says Prof. Bockmühl. (Fp)