1 9 4 5 ▁to ▁F lem ing , ▁Fl ore y , ▁and ▁Ch ain . ▁ ▁War ▁meant ▁a ▁greater ▁inc idence ▁of ▁w ound ▁in fe ctions , ▁often ▁by ▁st ap hy loc oc cus ▁(" st aph ") ▁and ▁stre pt oc oc cus ▁(" st rep ") ▁b acter ia . ▁Since ▁demand ▁was ▁high ▁and ▁it ▁took ▁weeks ▁to ▁cultiv ate ▁pen ic ill in , ▁the ▁supply ▁of ▁pen ic ill in ▁ran ▁out . ▁Therefore , ▁Howard ▁Fl ore y ▁and ▁Norman ▁He at ley ▁accepted ▁an ▁inv itation ▁by ▁the ▁Rock ef eller ▁Foundation ▁to ▁come ▁to ▁North ▁America ▁to ▁round ▁up ▁production ▁capacity . ▁In ▁Toronto , ▁D rs . ▁Phill ip ▁Gree y ▁and ▁Alice ▁Gray ▁of ▁the ▁University ▁of ▁Toronto ▁Department ▁of ▁Path ology ▁and ▁B acter i ology ▁began ▁this ▁work ▁in ▁collaboration ▁with ▁D rs . ▁C . C . ▁Lucas ▁and ▁S . F . ▁Mac Donald ▁of ▁the ▁B ant ing ▁Institute . ▁ ▁Following ▁initial ▁adv ances ▁in ▁chemical ▁prepar ation , ▁the ▁National ▁Research ▁Council ▁of ▁Canada ▁arranged ▁for ▁large - scale ▁production ▁via ▁the ▁Con n aught ▁Labor ator ies ▁in ▁ 1 9 4 3 . ▁The ▁work ▁" was ▁carried ▁on ▁twenty - four ▁hours ▁a ▁day , ▁seven ▁days ▁a ▁week ", ▁and ▁involved ▁heavy ▁collaboration ▁across ▁Boston , ▁Toronto , ▁New ▁York , ▁and ▁Oxford . ▁It ▁was ▁effectively ▁" a ▁major ▁military ▁operation ▁at ▁the ▁L abs ",