How to Have idxlayout Not Treat dotfill as Part of the Index Entry?

I am trying to incorporate the effect of dotfill in producing an Index with the idxlayout package.

I have tried this very (basic) approach:

documentclass[12pt]{book}
usepackage{imakeidx}
makeindex
usepackage{idxlayout}

begin{document}
Sentenceindex{Index entry1}
newpage Another Sentenceindex{Index entry2 dotfill}
idxlayout{columns=1}
printindex
end{document}

which prodices the following output for the Index:

I can see why Latex is treating dotfill as part of the entry, as evidenced by the comma appearing at the end of the sequence of dots.

My QUESTION is: How may I have the comma appear after `Index entry2′ followed by the sequence of dots leading to the page number?

I would like to be able to mimic somewhat, the Index from a very old book—but would like to be able to incorporate a comma.

Thank you.

delim_0 " dotfill "

documentclass[12pt]{book}
usepackage{imakeidx}
makeindex[options=-s dotted]
usepackage{idxlayout}

begin{document}
Sentenceindex{Index entry1}
newpage Another Sentenceindex{Index entry2}
idxlayout{columns=1}
printindex
end{document}