Impact ofVerification MediaandResuscitation onAccuracy oftheMembraneFilter Total Coliform Enumeration Techniquet

broth andECbroth secondary media. Verification inm-LAC broth yielded thegreatest numberofaerogenic isolates forbothuntreated surface wateranddrinking watersamples. Verification inbrilliant green-lactose-bile broth increased thenumber offalse-negative reactions. Atleast 90%oftheisolates aerogenic inprimary verification mediaandanaerogenic inbrilliant green-lactosebile broth wererepresentative ofthecoliform genera. Theaddition ofaresuscitation stepinthemembrane filter technique didnotyield greater numbers of verified coliforms persample. Verification ofbothtypical andatypical colonies in m-LACbroth resulted ina10-fold increase incoliform numbers fromuntreated surface water. Withdrinking water, verification ofbothcolony types resulted in anincrease fromless than1coliform per100mltogreater than1/100 ml.A single-step verification inm-LACbroth isproposed asamorerapid andsensitive coliform verification procedure thanthestandard technique. Themonitoring ofwatersupplies forthepresenceoftotal coliform bacteria isonemeansby whichthesanitary quality ofthesupply isdetermined. Thepresence ofanycoliform bacteria indrinking waterisanindication ofacontaminatedsource, inadequate treatment, orposttreatment contamination andmaybeofsanitary significance (4,7,19). Inuntreated surface waters thenumberofcoliforms present isanindex oftheoverall sanitary quality. Twoprocedures, themembrane filter (MF) andmost-probable-number methods, arerecognized fortheenumeration oftotal coliforms in watersamples (1, 23). Ofthetwotechniques, the MF procedure isusually themethodofchoice (11, 17,18)andpotentially represents amore rapid, sensitive, andreproducible procedure thanthemost-probable-number