\documentclass{article} \usepackage{acro} \newrobustcmd*\newspecies[4][]{% \DeclareAcronym{#2}{ short = {#3} , long = {#4} , #1 , tag = species , first-style= long , format = \itshape }% } \newspecies{ecoli}{E.~coli}{Escherichia coli} \begin{document} First use: \ac{ecoli}\par Second use: \ac{ecoli} \end{document}