Comparison of sterilization times in membrane filter devices with microbial suspensions at different concentrations.

Abstract

Introduction. Sterilization of the membrane filter device used in water microbiology analysis is very important. Aim of the study. To compare the efficacy of sterilization by burning with alcohol and flaming with a Bunsen burner. Material and methods. Bacterial suspensions were prepared at different concentrations and for each concentration, each analyst studied 10 culture media for each time periods. The contaminated membrane filter funnels with the prepared samples were sterilized by flaming for 10, 20, 40 and 60 seconds. Then, the membrane filter was placed and 100 ml of sterile distilled water was filtered. Membrane filter was placed on appropriate growth medium and it was incubated. The same procedure was also carried out by burning with alcohol. Results. At 102 concentration, bacterial growth was not observed. At 103 concentration, bacterial growth was observed 6,66% of growth medium at 10 seconds. At 104 concentration, bacterial growth was observed 30% of growth medium at 10 seconds and 23,3% of growth medium at 20 seconds. At 105, 106 and 107 concentrations, bacterial growth was observed in different percentages at all the time periods. Bacterial growth was not observed in sterilization using alcohol burning technique at all the time periods. Conclusions. Effective sterilization can be achieved by flame with Bunsen burner with low microbial concentration suspensions and low time periods. At high concentration suspensions, membrane filter device can be effectively sterilized by burning with alcohol. Key words: sterilization, sanitation, E.coli, Pseudomonas aeruginosa, membrane filter device, water quality.