Development of aggregating ability in cells of Streptococcus mitis ATCC 903 grown under glucose-limiting conditions in continuous culture

Abstract – Streptococcus mitis ATCC903 grown under glucose-limiting conditions in continuous culture did not aggregate upon incubation in 10_mM phosphate buffer at pH 5–7 unless a metabolizable sugar was added. aggregation started 45–50 min after the addition of glucose or sucrose whereas slowly metabolized sugars as gadlactose and lactose required several hours to cause aggregation. Active metabolism of the carbohydrate was a prerequisite for aggregation as indicated by acid formation. Chloramphenicol inhibited the development of aggregating ability in the presence of glucose or sucrose. The addition of a source of nitrogen (peptides and amino acids) enhanced aggregation and shortened the time for development of aggregating ability. No aggregation occurred at 0°C and the ability to aggregate was markedly delayed at 20°C as compared to 30°C. Trypsin treatment of the bacteria abolished aggregation, indicating that surface components of protein or glycoprotein nature contributed to the capacity to aggregate.     

Ultrasonic dispersion of pure cultures of plaque bacteria and plaque

Abstract – This study compared th somic sensitivity of 12 Gram-negative and two Gram-positive bacteria commonly encountered in plaque associated with periontal diseases. Pure bacterial cultures were groun to standard turbidity, diluted in 1/4 strength jprereduced anaerobically sterilized Ringer's solution, and aliquots dispersed for 0–180s, using and MSE sonic oscillator at 6 μm under 80% N² 10% H² and 10% CO². 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. viscosus was more resitant 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 Racteroides, and B. melaninogenicus ss. intermedius ressted 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 5–10s. Recoveries from plaque taken from five patients with periodontal diseases increased with sonication time, reaching higher values for supragingival than for subgingival samples.     

Diversity of Veillonella spp. from subgingival plaque by polyphasic approach

Leuckfeld I, Paster BJ, Kristoffersen AK, Olsen I. Diversity of Veillonella spp. from subgingival plaque by polyphasic approach. APMIS 2010; 118: 230–42. In a biofilm such as the subgingival microflora, strain‐specific properties or factors induced by the host may impart a survival advantage to some bacterial strains. Periodontal disease has been associated with chronic obstructive pulmonary disease (COPD) and we previously found high amounts of Veillonella in the subgingival microflora of COPD subjects. Differentiation of Veillonella is difficult. The aims of this study were to identify subgingival Veillonella isolates by phenotypic, genetic typing and molecular genetic methods, and further, to assess if Veillonella strain properties or identity correlated with periodontal disease or COPD. From 22 subjects, 26 subgingival Veillonella isolates and one pulmonary isolate were analysed. The majority of the subgingival Veillonella isolates were identified as Veillonella parvula. Genotyping showed heterogeneity within strains of the same species. A subgingival and pulmonary isolate in one COPD subject was found to be genetically identical strains of V. parvula. Scanning electron microscopy of the lung biopsy confirmed single small cocci adhering or coaggregating with larger cocci on the airway epithelium. Apart from a variation in cellular fatty acid composition of six subgingival isolates from periodontitis subjects, no correlation between the subgingival Veillonella strains or genotypes and the presence of either periodontitis or COPD was found. In conclusion, V. parvula was the predominant subgingival Veillonella species with high genetic variability within strains of the same species. Subgingival V. parvula can translocate to the lungs; however, Veillonella identity or genotype did not correlate with periodontal disease or COPD.