Jokes about BACTERIA

Two doctors met in the hall of the hospital.

"Well," said the first, "what's new this morning?"

"I've got a most curious case. Woman, cross-eyed; in fact, so cross-eyed that when she cries the tears run down her back."

"What are you doing for her?"

"Just now," was the answer, "we're treating her for bacteria."

ba domp bomp....!

I do not get that joke. Someone help me. Is it gross?

Back-tear-ia