Isolation of acholeplasmas and a mycoplasma from vegetables

Abstract

The isolation of Mollicutes from food has not been reported. To isolate Mollicutes in the presence of high levels of unwanted bacteria, the authors first incubated fresh vegetables in liquid culture media containing lysozyme, ampicillin, and thallous acetate. Culture fluids were then separated from the vegetable samples, subjected to one freeze-thaw cycle, and passed through a filter of 0.4-μm porosity. Filtered samples were cultured in SP4 medium and in a conventional medium containing horse serum. With this procedure 21 acholeplasma isolations representing 3 species were obtained from endive, broccoli, and kale. Of 35 food samples tested, 11 were positive for acholeplasmas; acholeplasmas isolated from 6 of these samples were recovered only in SP4 medium. In 7 single vegetable samples, 2 or more Acholeplasma spp. were isolated. A. laidlawii was isolated from all 3 vegetables and A. axanthum was found in broccoli and kale. 4 isolates were serologically identifed as A. oculi. Mycoplasma verecundum was the only Mycoplasma species recovered. Several isolates could not be typed serologically, as they reacted with antisera to both A. morum and A. hippikon. These isolates may include new Acholeplasma spp.