Sonic Energy as a Lethal Agent for Yeast and Bacteria

Abstract

Crystalline quartz has a certain characteristic which is fundamental to the experiments which we have performed. It is piezo active. Wood and Loomis have described an apparatus which we have utilized with certain modifications and which gives rise to the piezo effect. With this apparatus we have conducted certain experiments dealing with the killing effect of this source of energy upon bacteria and yeasts.' Wood and Loomis (1927) have demonstrated that ultrasonic radiation can disrupt certain higher forms of life. Williams and Gaines (1930) have shown germicidal effect of this wave motion but they used much lower frequency than that which we have applied. Harvey and Loomis (1929) demonstrated the death of luminous bacteria within 1 and 11 hours when treated by this energy. Chambers and Flosdorf (1936) have utilized a low frequency for extraction of certain fractions of the bacterial body. The reader is referred to the description of Wood and Loomis for an understanding of the principles involved and of the circuit utilized. We departed from their type in certain respects, as follows. The generator consisted of a circular cast-bronze housing of approximately 20 cm. diameter at the bottom and curved inward to 10 cm. in diameter at the top. One side was grounded. The bottom of this container was of plate glass and upon it was supported a flat-topped mushroom-shaped electrode upon which 361 JOU=AL 01 RAC Y, vo 32, x0. 4

The Lethal Action of Ultrasonic Waves on Bacteria Suspended in Milk and Other Liquids

“…Although the protective effect of whole milk observed by Beckwith & Weaver (1936) had been confirmed, it was remarkable that the reconstituted skim mill< was not equally effective, since those workers had ascribed the milk effect to the casein content, and the 8% concentration had been used because it was presumed that its protein content would have been roughly equal to that in fresh milk, i.e. about 40/,, the other 4O/, being lactose and salts.…”

“…The bacteria already mentioned were exposed to ultrasonic waves a t one or both of the frequencies available. Most of them were treated in three different liquids, as it was known (Beckwith & Weaver, 1936) that the suspension medium could exert a marked effect on the destructive effect produced. The fluids were: nutrient broth, an So/, (w/v) solution of dried skim milk, and glass-distilled water.…”

“…The tendency for certain of the graphs to depart from strict rectilinearity is evident: this will be referred to again later. As regards protective ability, the removal of the fat from fresh milk resulted in the loss of much of the protective effect, so the conclusion of Beckwith & Weaver (1936) that the casein was responsible does not seem wholly justified. However, emulsified fat by itself had little or no protective action, I n view of this, and of the fact that reduced protective ability was shown by homogenized milk, it appears that milk fat may only exert an influence if the globules are normal.…”

“…The great influence exerted by the suspending fluid on the effect produced was observed by Beckwith & Weaver (1936), who found that milk had a protective action on bacteria suspended in it. This they attributed to the physical structure of its casein constituent.…”

Effect of ultrasonic instrumentation on Bacteroides intermedius

“…These phenomena have been investigated using the Cavi-Endo ultrasonic endodontic unit by Ahmad et al (2). Studies in other disciplines have shown that these phenomena could cause cell disruption (3,4).…”