▁risk ▁for ▁S . ▁py ogen es ▁in fe ctions . ▁C lin ical ▁manifest ations ▁are : ▁p neum onia , ▁sept ic ▁ar th rit is , ▁ne c rot izing ▁fas ci itis , ▁and ▁gen ital ▁tract ▁se ps is . ▁According ▁to ▁a ▁study ▁done ▁by ▁Queen ▁Charlotte ' s ▁hospital ▁in ▁London ▁during ▁the ▁ 1 9 3 0 s , ▁the ▁v ag ina ▁was ▁not ▁the ▁common ▁source ▁of ▁such ▁in fection . ▁On ▁the ▁contrary , ▁mat ernal ▁thro at ▁in fection ▁and ▁close ▁contacts ▁with ▁carri ers ▁were ▁the ▁more ▁common ▁sites ▁for ▁mat ernal ▁S . ▁py ogen es ▁in fection . ▁ ▁B acter i ology ▁ ▁Ser ot yp ing ▁▁ ▁In ▁ 1 9 2 8 , ▁Reb e cca ▁L ance field ▁published ▁a ▁method ▁for ▁ser ot yp ing ▁S . ▁py ogen es ▁based ▁on ▁its ▁cell - wall ▁pol ys ac char ide , ▁a ▁vir ul ence ▁factor ▁displayed ▁on ▁its ▁surface . ▁Later , ▁in ▁ 1 9 4 6 , ▁L ance field ▁described ▁the ▁ser olog ic ▁classification ▁of ▁S . ▁py ogen es ▁isol ates ▁based ▁on ▁their ▁surface ▁T - ant igen . ▁ ▁Four ▁of ▁the ▁ 2 0 ▁T - ant ig ens ▁have ▁been ▁revealed ▁to ▁be ▁p ili , ▁which ▁are ▁used ▁by ▁b acter ia ▁to ▁attach ▁to ▁host ▁cells . ▁As ▁of ▁ 2 0 1 6 , ▁a ▁total ▁of ▁ 1