TEL AVIV, Israel, May 19 (UPI) -- A pocket-size breath test shows if bacteria are in the mouth and suggests using a toothbrush before attempting to kiss, Tel Aviv University researchers said.

Mel Rosenberg and Dr. Nir Sterer of Tel Aviv University said that until now, scientists believed that only one population of bacteria -- gram-negative ones -- break down the proteins in the mouth and produce foul odor.

The researchers discovered that the other population of bacteria -- the gram-positive ones -- are bad breath's bacterial partner. These bacteria appear to help the gram-negative ones by producing enzymes that chop sugary bits off the proteins that make them more easily degraded.

Rosenberg said this enzymatic activity, present in saliva, serves as the basis for the new "OkayToKiss" breath test.

"All a user has to do is dab a little bit of saliva onto a small window of the OkayToKiss kit," Rosenberg said in a statement. "OkayToKiss will turn blue if a person has enzymes in the mouth produced by the gram-positive bacteria. The presence of these enzymes means that the mouth is busily producing bacteria that foster nasty breath."

The findings have been published in the Journal of Breath Research.