Abstract: A method and apparatus for testing of solutions, such as antibiotic solutions to determine the presence of microorganisms, in which the solution is flowed through a plastic cylinder having a microporous membrane filter which strains microorganisms from the solution and concentrates them on the filter and thereafter the cylinder is flushed with a sterile solution, followed by filling the cylinder with an appropriate growth culture medium with the filter being vented, during this step, through a vent having a hydrophobic filter to prevent intake of bacteria. The presence of microorganisms in the original solution to be tested is determined by visual observation of the turbidity of the growth solution after an appropriate incubation period at suitable temperature. Where more than one microorganism is being tested for, aliquots of the test solution are flowed into identical plastic cylinders. The cylinders are intended to be disposables constructed economically enough to be thrown away after each test.