plural, pleural

Plural or plural describes a word form used to refer to more than one person or thing--
"They" is plural; "he" is singular.
The plural of "goose" is "geese".
Plural may describe a verb form with more than one subject--
That's "we are"; the subject is plural, so the verb should be plural.
Plural may mean more than one, in a general sense--
Utah banned plural marriage so that it could become a state.

Pleural or pleural ( rhymes with plural ) is a medical term that describes something related to the pleura, or membranes around the lungs--
He has pleural pneumonia; he'll be out of work for a few weeks.
His pleural infection is serious; he's not getting any better.

Now that you know that, you can say--
"The pleural infection is proving resistant to a plural dose of antibiotics."