When you're working your five-speed transmission like Sammy Hagar in a black Ferrari, the last thing on your mind is microbial infection. Then again, you might want to wear some gloves the next time you grab the stick and rev the engine or, at the very least, wash your hands thoroughly when you arrive at your destination. Why? Because the operative word in "manual transmission" is "manual." Even on a short trip, your hand spends a lot of time caressing the gearshift knob -- and picking up microorganisms that might be living there.
A tiny 2010 experiment in the U.K. supports this idea [source: Whitcroft]. Scientists swabbed 12 ordinary items in a suburban family's home, then tested those items for the presence of bacteria, including E. coli and Staphylococcus aureus, and two types of molds, aspergillus and penicillium. One of the things they tested was the gearshift knob of a 3-year-old Saab. Turns out, the knob was contaminated with high levels of bacteria and very high levels of molds. The researchers surmised that drivers pick up mold spores on their way to their cars. They then carry those spores into the vehicle and seal themselves inside with the contaminants. If you suffer from allergies or other respiratory problems, driving 55 may be the least of your worries.