A membrane filtration method for estimating the number of viable bacteria in solutions containing antibiotic

The method involves filtration of dilutions of the mixture through a membrane filter followed by replication on ox blood agar and enumeration of organisms. This method was compared with the conventional drop count method, and a significant correlation was found (r = 0.985). When solutions containing antibiotic were used, the membrane filtration method gave a more reliable estimate of the viable count at the time of sampling.