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Biomedical subjects

J de Graaff

Publications and source records attributed to J de Graaff.

177 records · Page 10Linked to original sources
PubMed1975

A genetic study of tolerance and resistance to colicin A in Citrobacter freundii.

Colicin A-insensitive mutants of Citrobacter freundii were isolated and grouped into six phenotypic classes characterized by sensitivity, insensitivity or partial insensitivity to the bacteriocins S6, DF 13 and colicin A, and sensitivity or insensitivity to deoxycholate (DOC) and ampicillin. Mapping by the gradient-of-transmission method revealed the chromosomal regions in which the responsible genes are situated. Res-3 mapped near pur between pur and thr; Tol-5 mapped between aro and ilv and Tol-4 between gal and pur; Tol-1, Tol-2 and Tol-3 are situated close to gal. All the mutations that mapped near gal rendered the bacteria more sensitive to DOC and ampicillin. Complementation analysis with E. coli plasmids showed that the three phenotypic groups that map near gal were complemented by E. coli plasmids and fall into three complementation groups. Two of these are quivalent with the tol A and tol B genes in E. coli.

Chromosome Mapping↗
PubMedDate not supplied

The role of Actinobacillus actinomycetemcomitans in periodontal disease.

The different forms of periodontitis are all associated with a distinct bacterial flora. However, a clear relationship is described between localized juvenile periodontitis (LJP) and Actinobacillus actinomycetemcomitans. Eleven LJP patients all harboured A. actinomycetemcomitans. The arrest of LJP is often impossible, due to the inability to eliminate A. actinomycetemcomitans. Therefore, antibiotic treatment was introduced in combination with the initial treatment. We studied the effect of periodontal treatment on the microflora and clinical status of periodontal disease patients using different therapies. Group 3 attained the best results (initial treatment and a combination metronidazole and amoxicillin), the group to eliminate A. actinomycetemcomitans effectively.

Actinobacillus↗
PubMedDate not supplied

Taxonomy, virulence and epidemiology of black-pigmented Bacteroides species in relation to oral infections.

Black-pigmented Bacteroides species are recognized as suspected pathogens of oral infections. Developments in the taxonomy of this group include description of a new asaccharolytic species, Bacteroides salivosus, and proposal for the reclassification of the asaccharolytic species into a separate genus, Porphyromonas. Studies on the pathogenicity and virulence of black-pigmented Bacteroides species have identified Bacteroides gingivalis as the most virulent species. B. gingivalis and Bacteroides intermedius have been associated with periodontal diseases; Bacteroides endodontalis is isolated specifically from infections in the oral cavity, and other black-pigmented Bacteroides species are recovered from oral mucous sites. DNA restriction endonuclease analysis was adapted for typing of B. gingivalis and B. intermedius.

Bacteroides↗
PubMedDate not supplied

Sealing of occlusal hidden caries lesions: an alternative for curative treatment?

The bacterial composition of the dentine of thirty molars with sealed occlusal surfaces (Delton tinted) was examined. Undiagnosed hidden caries was present at the time of treatment. Although clinically assessed as good (age 3.4 years, s.d. 2.1), 47 percent of the sealants had a marginal defect, when assessed with SEM. The dentine of the treated teeth was of a soft consistency. The median of the number of microorganisms was 400 (range 0-3.10(5)) cfu per sample. Mutans streptococci and lactobacilli were found in 53 percent of the samples. No relationship was found between the number of microorganisms and the marginal adaptation of the sealant, when examined under SEM; neither was a relationship found between the age of the sealant and the number of microorganisms (Kendall's Tau-C = 0.17, n.s. and -0.01, n.s., respectively). At present, there are insufficient grounds for treating nonvisible lesions (with a radiolucency on the bitewing) with a resin sealant.

Actinomyces↗
PubMedDate not supplied

Prevalence of Streptococcus sobrinus in relation to dental caries in children from Iceland and The Netherlands.

The aim of this study was to investigate the presence of S. sobrinus and S. mutans in specimens of dental plaque and saliva of children five years of age in Reykjavik, Iceland (study 1) and in samples of dental plaque from children nine years of age in Amsterdam, The Netherlands (study 2). The immuneblotting technique (IBT) was a suitable method to evaluate the presence and numbers of S. mutans and S. sobrinus in human dental plaque and saliva. In study 1, eighty-four children were evaluated bacteriologically; of these, 73 percent harbored mutans streptococci in their plaque or saliva. S. sobrinus similarly was present in 29 percent of the children. In study 2 (seventy-two children), the corresponding percentages were 81 percent for S. mutans, and 35 percent for S. sobrinus. The latter was detected in 6 percent of the plaque samples exclusive of S. mutans.

Child↗
PubMedDate not supplied

Occlusal hidden caries: a bacteriological profile.

Eleven teeth from nine patients with occlusal caries lesions beneath an apparently intact enamel surface were treated. Two dentine samples, one from the dentinoenamel junction (Sample A) and one just before all the caries appeared to be removed clinically (Sample B), were taken under aseptic conditions and examined for bacteria. In all cases, the A samples and in ten cases the B samples contained mutans streptococci, lactobacilli or both, while in ten cases the dentine after opening was soft with a light color. This suggests that we are dealing with active caries lesions, which should be treated as such. The salivary data of the patients group were compared with the salivary data of the control group. Although the buffer capacity of the groups were not significantly different (chi-square), further analysis revealed that a significant relationship could be found between the group and the buffer capacity (Kendall's Tau C). While the other salivary components (numbers of mutants streptococci per ml saliva and the secretion rate) showed no significant differences. Unfortunately these occlusal caries lesions are not detected with the present criteria used in epidemiological surveys.

Chi-Square Distribution↗
PubMedDate not supplied

Hygiene in dental practice--Part I: Potential pathogens and possibilities of contamination.

In order to ensure adequate reduction of risks of contamination in dental practice, potential pathogens should be known and insight should be gained into possibilities of contamination. The first part of this article presents brief descriptions of the most relevant pathogenic microorganisms such as the causative agents of tuberculosis, gonorrhoea, syphilis, herpes simplex, hepatitis, AIDS and legionnaires' disease. Possibilities of contamination in dental practice are considered next, with special reference to various ways in which microorganisms can be transmitted: Hand instruments. Rotating instruments, multiple-function syringe and ultrasonic scaler. Instruments used in endodontics. Hands and face. Clothing. Treatment unit. Measures that can be taken in order to minimize the risk of contamination will be discussed in Part II.

Bacterial Infections↗
PubMedDate not supplied

Hygiene in dental practice. Part II: Measures to reduce the risk of contamination.

On the basis of the description of potential pathogens and possibilities of contamination during dental treatment in Part I, Part II discusses several measures to be taken, in order to reduce the risk of contamination for patients as well as for dental personnel. The hygienic measures mostly concern the treatment of patients, including some unidentified infected patients. In this context, direct and indirect behavior of dental personnel, protective measures, domestic cleaning, disinfection, and sterilization are discussed in detail. In addition, possible supplementary measures to be taken in the treatment of identified infected patients are discussed, with special reference to hepatitis B and HIV. Finally, hygienic measures to protect personnel not directly involved in dental treatment are discussed.

Communicable Disease Control↗