A team of German microbiologists has tackled the issue of bacteria on kitchen sponges by testing 14 sponges for their presence and identifying them by extracting and sequencing segments of their DNA. There were dozens and dozens of microbes, most of them innocuous, but some capable of causing disease. The study generated lots of media attention with headlines like 鈥淜itchen Sponges are Dirtier Than Toilet Seats鈥� and 鈥淜itchen Sponges are Festering Germ Dens.鈥�
Actually finding that sponges teem with bacteria is no great surprise, after all bacteria are everywhere; they鈥檙e on our cellphones, door handles, faucets, benches, clothes, banking machines, stethoscopes, credit cards, money and of course our bodies. In fact, there are more bacterial cells in our body than human cells! Of course, most of the time bacteria do not bother us, we happily share our world with them. What was surprising in this case, was the ability of some microbes to survive microwaving and the high temperatures in a dishwasher. Furthermore the pathogenic, or disease causing, bacteria were the ones more likely to survive, but that would need to be further explored due to the small sample size here. Also, curiously, there is no mention in the paper about how long the sponges were exposed to microwaves. Probably not long enough, given that there are actually studies demonstrating that microwaving a wet sponge at high for two minutes destroys all microbes.聽
To be clear, this study did not look for any connection between the dirty sponges and human ailments. Just because sponges may be teeming with bacteria does not mean they are spreading disease. That would be very difficult to pin down, although somewhat easier with currency. Paper or plastic bills are a great breeding ground for germs and by tracking money that had been assayed for bacteria it may be possible to determine if an outbreak of some infectious disease is linked to some specific microbes on the bills themselves.
All this being said, the only legitimate conclusion to be drawn from this study is that kitchen sponges harbour a large variety of bacteria and that a cycle in the dishwasher is not likely to destroy them. As far as microwaving goes, no firm conclusion can be drawn because no length of time was mentioned. I do still think that two minutes of microwaving every couple of days basically eliminates the contamination problem.
Is it better to wipe the countertop with a paper towel? Even aside from the ecological problem of using paper, the issue is not clear. A better experiment would have been to test kitchen countertops that had been wiped with a sponge or cleaned by some other means for bacterial contamination. My guess is that if a small amount of commercial spray that contains hydrogen peroxide or bleach is applied to the counter, it doesn鈥檛 matter what is used to wipe it.
Finally, there is the bothersome 鈥渉ygiene hypothesis鈥� with its suggestion that we are seeing more allergies and more autoimmune reactions because of our great attention to cleanliness leading to a reduced exposure to bacteria. It seems that if our immune system isn鈥檛 trained to attack a bacterial target, it will unleash its weaponry against innocent bystanders like pollen or the body鈥檚 own tissues. But that鈥檚 only a theory.聽
Bottom line? Despite the publicity garnered by this study of kitchen sponges, it doesn鈥檛 add very much to what we already know.
