Tooth decay bacteria

The NY Times says that you can blame moms for tooth decay:

If the tooth decay bacterium spreads easily from person to person, any geographical pattern would soon be blurred. But Streptococcus mutans is transmitted almost entirely from mother to child, preserving its lineages over thousands of years. The bacteria apparently infect the infant during birth, beginning the work that provides the dentistry profession its livelihood. We’ve never seen father-to-child transmission," Dr. Caulfield said. Thanks, Mom.

Now that they have identified the bacteria, why can't they kill it?