Certainly isn't news. I was taught about cladisporium resinae (possibly a bit hazy memory of the name!) when doing RAF engineer training in 1977 and it wasn't a new discovery then. Moreover, the addition of Fuel System Icing Inhibitor (FSII) to Avtur had the side effect of preventing the growth - bonus!
So long as you did water drain checks, things were fine - I remember a 125 that needed a huge underwing repair at McAlpine's in the 70s because of this.