Ultrasonic dispersion of pure cultures of plaque bacteria and plaque

This study compared the sonic sensitivity of 12 Gram-negative and two Gram-positive bacteria commonly encountered in plaque associated with periodontal diseases. Pure bacterial cultures were grown to standard turbidity, diluted in 1/4 strength prereduced anaerobically sterilized Ringer's solution, and aliquots dispersed for 0-180 s, using an MSE sonic oscillator at 6 micron under 80% N2, 10% H2 and 10% CO2. Viable recoveries were determined on anaerobically cultured trypticase soy 5% blood agar plates. Breakage of T. denticola was assessed by electron microscopy. Gram-positive organisms tolerated sonication better than Gram-negative. A. viscous was more resistant than Strep sanguis. Gram-negative bacteria could be divided into groups according to their sensitivity. Eikenella corrodens was most resistant, followed by F. nucleatum B asaccharolyticus, Capnocytophaga gingivalis, A actinomycetemcomitans, a strain (2097) of Group IV Bacteroides, and B melaninogenicus ss intermedius resisted sonication better than "corroding' Bacteroides and oral Campylobacter. T. denticola, Selenomonas sputigena and Wolinella were most sensitive with viable counts which declined after sonication for 5-10 s. Recoveries from plaque taken from five patients with periodontal diseases increased with sonication time, reaching higher values for suprangingival than for subgingival samples.