The moral to this story is that the good research scientist pays strict attention to any peculiar event and does not shrug off a mystery as just one of those things.

“A'ight, you keep on waiting. She gon' fuck around and find out on her own”.

The young man's lucky star shone full on him, and dazzled him to a seeming indiscretion.

Note that L. monocytogenes is one of the few Gram-positive bacteria against which vancomycin is not effective — hence the need for ampicillin.