UseoftheBac-T-Screen toPredict Bacteriuria fromUrine Specimens HeldatRoomTemperature

Results fromtheBac-T-Screen (BTS) offresh urinespecimens werecompared withtheBTSresults obtained whenthe same urine specimens hadbeenheldatroom temperature for24h.Ofthe246specimens studied, 43 wereinitially BTSpositive, 11werefalse-negative, and39had2105 CFU/ml. After 24hatroom temperature an additional 60specimens had'105CFU/ml, ofwhichonly16were BTSpositive; 10specimens still gave false-negative results, andthenumberoffalse-positive specimens increased byonly 6.5%ofall specimens. For significant specimens (containing :-05CFUofprobable pathogens perml), thepredictive value ofanegative test changed byonly0.1%(99.5 to99.4%), whereas thesensitivity ofthetest remained at96.4%forincubated specimens. Ofthose specimens thatdeveloped '105CFU/mlinvitro, 85% contained gram-negative bacilli. Neither bacteria grown invitro nor urine specimensfromnormalfemales containing 2105CFU/mlwere positive with the BTS. For reasons not entirely understood, theBTSsystem may beunique initsability to discriminate between bacteria whichrepresent truebacteriuria andthosewhicharepresent because of contamination, possibly duetoothercellular elements present ininfection-related