Inhibition of Moraxella‐Acinetobacter Cells by Sodium Phosphates and Sodium Chloride

Abstract

ABSTRACT The effect of sodium phosphates with and without NaCl, on the ability of unstressed and heat‐stressed Moraxella‐Acinetobacter (M‐A) isolate number 7 cells to form colonies in plate count agar (PCA) was determined. The effectiveness, in order of decreasing ability, of phosphates to inhibit colony formation of unstressed M‐A cells was as follows: sodium tripolyphosphate (Na 5 P 3 O 10 ; STPP), sodium pyrophosphate (Na 4 P 2 O 7 ; SPP), and sodium orthophosphate (Na 3 PO 4 ; SP). Filter sterilized STPP was more inhibitory than when heated and inhibition was not related to pH. Certain combinations of NaCl and STPP were additive whereas combinations of NaCl and SPP exhibited a synergistic effect. Heat‐stressed M‐A cells were more sensitive to levels of NaCl (0.8%) than to levels of STPP (0.1%) or SPP (0.12%); all shown to have no effect on the number of colonies formed in PCA by unstressed cells.