Glucanase-producing organisms in human dental plaques.

Selective media were used to isolate a wide range of bacteria from sixty human dental plaques. Glucanase activities of the isolates were determined on dextran- and starch-containing media. All sixty samples of dental plaque yielded some colonies showing amylolytic and dextranolytic activities. The glucanase-producing organisms comprised 20% of the isolates. Of these 38% were Gram-positive rods, 27% Gram-positive cocci, 28% Gram-negative rods and 7% were Gram-negative cocci. The cultural groups most commonly represented among the glucanase-producing isolates were Actinomycetaceae, streptococci, haemophili and Gram-negative anaerobes. Species prominent among these isolates included Streptococcus sanguis, Streptococcus mitior, Actinomyces naeslundii, Actinomyces viscosus, Bacterionema matruchotii, Bifidobacterium sp. and Bacteroides sp. No isolates capable of degrading starch or dextran were identified as Streptococcus milleri, Rothia dentocariosa or Fusobacterium sp. This study has shown that a wide range of bacterial species commonly isolated from human dental plaques exhibit both amylolytic and dextranolytic activities. In order to understand glucan metabolism in human dental plaques further investigation of these catabolic activities is necessary.     

Selectivity of Mitis Salivarius agar and a new selective medium for oral streptococci in dogs

An evaluation on the applicability of Mitis Salivarius agar (MS) medium, commonly used for the detection of oral streptococci in human and animals, to dog specimens and the development of a new selective medium for isolating streptococci from the canine oral cavity are described. Oral samples from dogs were cultured on MS medium under anaerobic conditions. The predominant facultative anaerobic bacteria on MS plates were gram-negative rods. Selectivity of streptococci on MS medium was 21.2%. A new selective medium, designated MS-CAN-AE, was developed for the isolation of streptococci from the canine oral cavity. The average growth recovery of laboratory and clinically isolated strains of streptococci on MS-CAN-AE medium was 84.1% of that on MS medium. Gram-positive rods and gram-negative rods and cocci rarely grew on the MS-CAN-AE. The selectivity of MS-CAN-AE was 95.0% for clinical samples. MS-CAN-AE medium will be helpful for investigations of streptococci in the canine oral cavity.     

A new selective and differential agar medium for Escherichia coli and coliform organisms

W right , R.C. 1984. A new selective and differential agar medium for Escherichia coli and coliform organisms. Journal of Applied Bacteriology 56 , 381–388.
An enriched lauryl sulphate-aniline blue agar medium which is selective for Escherichia coli and coliform organisms is described. From faecal samples, the medium gave higher counts of colonies producing acid from lactose than media containing bile salts. From contaminated water and food samples, the medium gave comparable or higher counts of colonies identified as E. coli than standard media. Colonies of E. coli were more readily differentiated from those of other coliform organisms.     

Evaluation of a new chromogenic agar medium for isolation and identification of Group B streptococci

AIMS: To evaluate a new chromogenic agar as a screening medium for the isolation of Group B streptococci from high vaginal swabs from pregnant women. METHODS AND RESULTS: The medium was evaluated with 195 high vaginal swabs referred for antenatal screening and compared with blood agar and Granada medium. The new chromogenic medium showed 100% sensitivity for the detection of Group B streptococci, and also showed a positive predictive value of 100%. Granada medium also showed excellent sensitivity and specificity and both media were superior to blood agar. CONCLUSIONS: The new chromogenic medium showed excellent performance for the detection of Group B streptococci from clinical samples. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first chromogenic medium described for the detection of Group B streptococci. The medium offers an effective and convenient alternative to conventional media, currently used in clinical laboratories.     

Streptococcus mutans and oral streptococci in dental plaque

The human oral microbial biota represents a highly diverse biofilm. Twenty-five species of oral streptococci inhabit the human oral cavity and represent about 20 % of the total oral bacteria. Taxonomy of these bacteria is complex and remains provisional. Oral streptococci encompass friends and foes bacteria. Each species has developed specific properties for colonizing the different oral sites subjected to constantly changing conditions, for competing against competitors, and for resisting external agressions (host immune system, physico-chemical shocks, and mechanical frictions). Imbalance in the indigenous microbial biota generates oral diseases, and under proper conditions, commensal streptococci can switch to opportunistic pathogens that initiate disease in and damage to the host. The group of "mutans streptococci" was described as the most important bacteria related to the formation of dental caries. Streptococcus mutans, although naturally present among the human oral microbiota, is the microbial species most strongly associated with carious lesions. This minireview describes the oral streptococci ecology and their biofilm life style by focusing on the mutans group, mainly S. mutans. Virulence traits, interactions in the biofilm, and influence of S. mutans in dental caries etiology are discussed.     

Identification of streptococci in a medical laboratory

A total of 965 cultures of streptococci received at a reference unit for identification were examined with API-20 Strep kits and also by established methods. The API method, although it needed to be supplemented with additional tests, largely overcame the difficulty that pyogenic streptococci are usually identified by their serological reactions and that biochemical tests are used for the identification of the other streptococci. Representatives of at least 24 established or possible species were identified.     

Identification of streptococci in a medical laboratory

A total of 965 cultures of streptococci received at a reference unit for identification were examined with API-20 Strep kits and also by established methods. The API method, although it needed to be supplemented with additional tests, largely overcame the difficulty that pyogenic streptococci are usually identified by their serological reactions and that biochemical tests are used for the identification of the other streptococci. Representatives of at least 24 established or possible species were identified.     

Effects of agar brand and concentration on the tissue culture medium

In tissue-cultured Cynara scolymus L. (globe artichoke) vitrification (hyperhydric transformation) can only be overcome by increasing the concentration of agar. However, with increasing concentrations of Difco Bacto agar (8–15 g/I) the availability of labelled kinetin is decreased. There is some evidence for postulating that cytokinins under inductive conditions of low agar concentration or high matrix potential are evocators of vitrification.
Both the brand and concentration of agar also affect the chemical and physical characteristics of a culture medium.
Impurities introduced with the agar are responsible for significant differences in the concentration of an element in comparable media with different levels of agar, and are easily detected by conductance.
Penetrometer measurements also show large ranges in solidity of media with increasing concentrations, not only within the type of agar, but also for the same concentration within different brands.     

Enumeration of intestinal enterococci and interfering organisms with Slanetz-Bartley agar, KF streptococcus agar and the MUST method

The recovery of intestinal species of enterococci and streptococci and potentially interfering nonfaecal species was measured on KF streptococcus agar, Slanetz-Bartley agar and in a medium based on 4-methylumbelliferyl-β- d -glucoside (MUST method) using pure cultures. Both of the solid media yielded high recoveries of the target species. Their selectivity was better at elevated incubation temperature but nonfaecal Enterococcus and Staphylococcus species were not eliminated even at the elevated temperature. The MUST method tended to give slightly lower recoveries than the agar cultivation methods with some target species at 44°C but recoveries were better at 41°C.     

Effect of the culture medium composition on bacitracin synthesis and sporulation in Bacillus lichenformis 28 KA

The effect of the culture medium composition on the bacitracin synthesis and sporulation in Bacillus licheniformis 28 KA was being studied. During the producer's growth on a medium with tripton a biphasic pattern of the process was observed, i.e. a rapid growth of the bacterial biomass was accompanied by the production of insignificant amounts of the antibiotic. The maximum efficiency of the antibiotic synthesis coincides with the end of the exponential growth phase and the onset of sporification. The efficiency of sporification amounts up to 95% when the above mentioned medium is used. The substitution of glutamate for trypton results in a dramatic deceleration of the bacterial growth and biomass accumulation, and the process of the antibiotic biosynthesis ceases to be biphasic, i. e. the antibiotic is synthesized during the trophophase. Under the conditions when the antibiotic production drops to zero by the middle of the exponential growth phase, sporulation is virtually suppressed.     

Nested PCR for detection of mutans streptococci in dental plaque

AIMS: Mutans streptococci such as Streptococcus mutans and Streptococcus sobrinus have been implicated in human dental caries. In an attempt to develop a rapid and sensitive method for detecting Strep. mutans and Strep. sobrinus in dental plaque, a nested PCR amplification based on the 16S rRNA gene was employed. METHODS AND RESULTS: A universal set of PCR primers for bacterial 16S rRNA gene was introduced for the first PCR, and then two sets of primers specific for the 16S rRNA gene sequences of either Strep. mutans or Strep. sobrinus were used for the second PCR. Eighteen plaque samples were analyzed, and a nested PCR was shown to be more sensitive for detecting Strep. mutans and Strep. sobrinus than direct PCR. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: The 16S rRNA gene-based nested PCR method is a rapid and sensitive method for the detection of mutans streptococci, and may also be suitable for carrying out large-scale studies on the cariogenicity of mutans streptococci.     

Glucose and penicillin concentrations in agar medium below fungal colonies

The growth of colonies of Rhizoctonia cerealis and Penicillium chrysogenum on solid media in plate cultures was studied. When grown on defined media containing 10-50 mM-glucose, R. cerealis did not cause a significant reduction in the glucose concentration of the medium in advance of colonization, but did cause the formation of a steep glucose concentration gradient in the substrate below the colony; the medium directly below the centre of a 7 cm diameter colony of R. cerealis was exhausted of glucose even when the fungus was grown on medium containing 50 mM-glucose. Penicillin produced by colonies of P. chrysogenum accumulated in the medium in advance of fungal colonization. For a period up to about 18 d after inoculation, the concentration of penicillin in the medium throughout the plate increased with colony development and thereafter, except at the margins of the plate, decreased.