THE USE OF STORED SUSPENSIONS OF ESCHERICHIA COLI I IN THE EVALUATION OF BACTERICIDAL ACTION

Abstract

S U M M A R Y :Suspensions of Escherichia coli I, consisting of washed cells suspended in a phosphate buffer solution, maintained a higher viability and resistance to phenol than suspensions either of unwashed cells or of washed cells suspended in water. When stored for 5 weeks at room temperature, variations in their extinction times on exposure to aqueous phenol solutions were not significantly greater than variations with suspensions freshly prepared for each determination. Loss of resistance of a stored suspension to phenol, roxenol, lysol and potassium laurate was roughly parallel. Conditions of culture of the bacteria influenced the survival of suspensions, hut the results indicated that pronounced differences may only be found in suspensions prepared from young cultures. The use of stored suspensions in the routine evaluation o f bactericides is recommended.

The antibacterial activity of chloroxylenol in combination with ethylenediaminetetra-acetic acid

“…Normally increased resistance of organisms to phenols is associated with increasing culture age (Cook & Wills, 1958). Cowen (1974) has shown that resistance ofPseudomonas spp.…”