Here's a real jolt for coffee drinkers: Researchers say there's a good chance that mugs kept at the office are crawling with countless critters, some harmless and some not.

Tiny troublemakers - including scary stuff like E. coli - are having population booms because people don't carefully wash out their cups or disinfect sinks and preparation areas in most offices."Ewwww! That's yucky!" said Gabriella Rico, a spokeswoman at the Pima County Juvenile Court Center, who identified herself as a coffee drinker. After learning about tests conducted by Charles Gerba and Ralph Meer of the University of Arizona, she had a change of heart.

"I take that back," Rico said. "I'm not a coffee drinker any more."

Gerba and Meer tested dishes, sinks, cups, dishrags, sponges, counters and spoons in at least a dozen offices in Tucson two years ago, publishing their results in a journal on dairy food and sanitation.

They tested from three to 12 cups per office, transferring samples taken with cotton swabs to a liquid medium and then to petri dishes. They tested the liquid squeezed from sponges and rags.

"The premise was that there's usually coffee and food preparation areas in offices, and usually these areas are not sanitary," Gerba said.

The leading culprits are sponges and rags. "We're finding that those things are pretty unsanitary," rife with coliform bacteria, Gerba said.

"In our study, about 40 percent of the cups had coliforms in them," he said. "That's usually indicative of unsanitary conditions."

Gerba said cups with lids were particularly effective bacterial breeding areas - occasionally for E. coli.

Escherichia coli is the name of a common family of bacteria, most of which do not cause human disease. One strain, E. coli O157:H7, lives in the intestines of cattle and can cause bloody diarrhea in humans who eat contaminated meat products.