Which mycologist first identified Fleming's mould as Penicillium rubrum?

Charles J. La Touche was the mycologist who first identified Fleming’s mould as *Penicillium rubrum*.

In 1928, Alexander Fleming asked La Touche, an Irish botanist and mycologist working at St Mary’s Hospital, to examine the blue-green mould contaminating a culture of *Staphylococcus aureus*. La Touche’s identification was the name Fleming used when he published his penicillin research in 1929.

The mould’s identity later became a taxonomic tangle. Charles Thom reclassified it as *Penicillium notatum*, and it was subsequently associated with *P. chrysogenum*. Modern genomic analysis published in 2011 concluded that Fleming’s strain is *Penicillium rubens*.

A common mix-up is Philibert Biourge, who described *P. rubens*, not the person who made Fleming’s original identification. Charles Thom was also involved in later reclassification, while La Touche supplied the identification used in Fleming’s landmark paper.