You grab a clean towel from the pile at the gym. What you can't see is that the fibers may be teeming with E. coli or MRSA. Most gyms use the same hamper to transport dirty towels and clean ones, Tierno says. Germ Warfare. Bring your own towel, marked with an X on one side with a permanent marker, Tierno advises; only that side should make contact with gym machines.