A modified method for the enumeration of aerobic spore-forming bacteria

Abstract

An optimized method for cultivating aerobic spore-forming bacteria in drinking water is described. Such organisms offer the potential as an indicator of water treatment efficiency. The various parameters evaluated were recovery media, incubation, and pasteurization conditions. The optimal conditions consisted of pasteurization for 15 min at 75 °C, followed by membrane filtration and incubation for 24 h at 35 °C on a pad to which 1.4 mL trypticase soy broth had been added. Aerobic spore-forming bacteria were detected in large numbers (1.0 × 10 2 − 3.2 × 10 3 CFU/100 mL) in raw waters and daily samples showed that in natural waters they remained stable over the test period (3 weeks).Key words: aerobic spores, method, indicator.