Getting a handle on bacteria


One of the main ways infection spreads in hospitals is by cross-contamination: someone touches a surface with bacteria on it, and carries them somewhere else.

The traditional way of dealing with such surface contamination is by regular cleaning with disinfectants.  But cleaning can be careless and inadequate, and can even contribute to the transfer of bacteria. A better solution would be to create surfaces which themselves kill the bacteria without any intervention from human beings.

Such surfaces exist. Certain metals seem to kill bacteria efficiently, by preventing respiration, inhibiting reproduction and disrupting metabolism, although it’s not quite clear how. Claims have been made for titanium and nickel, but the main competitors in the field are copper and silver.

Pure copper is very effective indeed, but scarcely ideal for door furniture: it's soft and tarnishes easily, and the use of waxes, polishes or coatings stop copper ions from getting out and doing their deadly work.

The use of silver has to be approached in a different way, since it would be prohibitively expensive to make door furniture out of silver. But small quantities of ionic silver appear to be very powerful. One company, Agion Technologies, hosts its silver ions, sometimes with zinc or copper, in a zeolite powder. Ions are released in response to moisture. Studies have shown that it too can reduce bacterial levels by more than 99.9 percent after two hours.

The additive has varied uses. As well as in health care, it may be found in air-conditioning systems, on computer keyboards and mice, mobile phones – even running shoes, to stop the smell of sweat. 

It’s also used in a coating for locks, levers and other architectural hardware products.