Go Figure

I don't know why it took me so long to do this search-

Nicotine has antimicrobial action against oropharyngeal bacteria.

Levels of inhibition  >50% occurred when most of the affected organisms were cultured with nicotine at 100-250 µg/ml.   It is noteworth that such concentrations of nicotine can be found in vivo, especially in the oral cavity of smokeless tobacco users, making these findings physiologically relevant. It should also be noted that the viridans streptococci that were used in these experiments- which were also highly susceptble to the effects of nicotine- are an almost universal inhabitant of the oropharynx.

Nicotine exposure may have a subtle beneficial effect on the host by limiting the growth of certain respiratory tract and enteric pathogens, as they enter the body through the oral and nasal passages.

Well, well, well.   How about that.
Probably explains why patches do not have the same effect.