On a "Seinfeld" episode, Jerry has given Kramer his spare keys, but keeps finding Kramer in his apartment at inopportune times.

Finally, Jerry brings a date home, only to see Kramer and his girlfriend emerging from his bedroom.

"All right, that's it. Hand 'em over," says Jerry. Finally, Kramer agrees to, but threatens, "You're going to regret this." Probably not.

Ushering out a "guest" who just won't leave is the same as KO-ing a stubborn bacterial infection and restoring your good health.

But what if you are infected with a bacteria that just won't go? It turns out that's sometimes the case with the Lyme disease bacteria.

A study in PlosOne reveals that the infection can linger after you've taken long-term antibiotics and tests show you're okay.

That's because it's possible for Lyme bacteria to survive the typical 28-day course of antibiotics.

In fact, surviving bacteria can migrate to organs like the heart and brain, even when tests for the bacteria show negative results.

So if you've been treated for Lyme disease and fatigue, joint pain, confusion, numbness, heart problems or other hard-to-figure-out symptoms persist, you're not crazy. Your symptoms well might be related to a continuing Lyme infection.

Make sure your doctor performs another blood test, and that you aren't misdiagnosed with some other disease.

It may be that Lyme is the cause of your symptoms and you need continued, aggressive treatment(s) such as IV antibiotics or other therapies for arthritis or neurological conditions.