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- Chávez de Paz, Luis, 1974
(författare)
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On bacteria Persisting Root Canal Treament. Identification and potential mechanisms of resistance to antimicrobial measures.
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Anti-microbial treatment of infected root canals using mechanical instrumentation and chemicals for disinfection does not always lead to complete bacterial elimination and treatment failure may therefore result. As certain bacteria appear more resilient to endodontic treatment than others, the present thesis addresses the species that can most frequently be isolated after treatment and explores mechanisms, which could potentially afford these organisms resistance to anti-microbial treatment measures.In an initial assessment, consecutive root canal samples from a total of 200 clinical cases were analysed for cultivable microbes. Patients had present with clinical and/or radiographic evidence of apical periodontitis. Root canal treatment had been initiated at one or more appointments prior to sampling. Results demonstrated a clear predominance of Gram-positive rods and cocci. These organisms outweighed other bacterial groups common in primary root canal infections including Gram-negative anaerobes.In a second study, a protocol for identification of Gram-positive rods at the species level was validated. Here, 86 cases presenting with Gram-positive rods in the first study as well as 53 new cases were included. Identification was based on a combination of selective media, gas-liquid chromatography and SDS-PAGE electrophoresis of whole-cell proteins. Of a total of 158 Gram-positive rods isolated, it was possible to identify 96% at the species level. The most common species were Olsenella uli, Lactobacillus paracasei and Propionibacterium propionicum.In a third study Streptococcus, being the second largest group of organisms isolated in the first study, were subjected to identification. Extra-cellular proteins produced in culture media were also screened. A total of 100 cases (45 from study I, 32 from study II and 23 new cases), which showed growth of streptococcal species were included. Criteria for identification were based on physiological characteristics. The most frequently isolated species were Streptococcus gordonii, Streptococcus anginosus and Streptococcus oralis. The protein release pattern expressed by clinical isolates was different from that of corresponding laboratory strains. S. gordonii, S. anginosus, S. oralis and S. parasanguis produced the molecular chaperone. DnaK extra-cellularly. The bacterial cell viability and protein response patterns to alkaline stress of collection of seven organisms, isolated in the previous studies, were assessed in paper IV. When tested under planktonic growth conditions, cells were found to be less viable after an alkaline challenge than corresponding cells growing in biofilms. Excretion of proteins appeared to be a rapid response of these organisms prior to a switch stationary phase. When these strains were grown in mixed cultures (community assessments - unpublished data), viability of cells seemed to be less affected by alkaline challenge. In addition, the rate at which bacteria switched into an inactive phase appeared to increased.In conclusion, Gram-positive rods and cocci seem to be the most enduring organisms in infected root canals subjected to endodontic treatment. The formation of biofilms and expression of a variety of proteins, as well as growth in mixed communities, may provide these organisms with the capacity to resist root canal treatment.
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| 2. |
- Chávez de Paz, Luis, 1974, et al.
(författare)
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Response to alkaline stress by root canal bacteria in biofilms. : Viability and mechanisms of response to alkaline stress by selected root canal bacteria.
- 2007
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Ingår i: International endodontic journal. - : Wiley. - 0143-2885 .- 1365-2591. ; 40:5, s. 344-55
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Tidskriftsartikel (refereegranskat)abstract
- AIM: To determine whether bacteria isolated from infected root canals survive alkaline shifts better in biofilms than in planktonic cultures. METHODOLOGY: Clinical isolates of Enterococcus faecalis, Lactobacillus paracasei, Olsenella uli, Streptococcus anginosus, S. gordonii, S. oralis and Fusobacterium nucleatum in biofilm and planktonic cultures were stressed at pH 10.5 for 4 h, and cell viability determined using the fluorescent staining LIVE/DEAD BacLight bacterial viability kit. In addition, proteins released into extracellular culture fluids were identified by Western blotting. RESULTS: Enterococcus faecalis, L. paracasei, O. uli and S. gordonii survived in high numbers in both planktonic cultures and in biofilms after alkaline challenge. S. anginosus, S. oralis and F. nucleatum showed increased viability in biofilms compared with planktonic cultures. Alkaline exposure caused all planktonic cultures to aggregate into clusters and resulted in a greater extrusion of cellular proteins compared with cells in biofilms. Increased levels of DnaK, HPr and fructose-1,6-bisphosphate aldolase were observed in culture fluids, especially amongst streptococci. CONCLUSIONS: In general, bacteria isolated from infected roots canals resisted alkaline stress better in biofilms than in planktonic cultures, however, planktonic cells appeared to use aggregation and the extracellular transport of specific proteins as survival mechanisms.
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| 3. |
- Chávez de Paz, Luis, 1974, et al.
(författare)
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Streptococci from root canals in teeth with apical periodontitis receiving endodontic treatment.
- 2005
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Ingår i: Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics. - : Elsevier BV. - 1528-395X .- 1079-2104. ; 100:2, s. 232-41
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: The object of this study was to investigate the diversity among streptococcal species isolated from root canals in conjunction with endodontic therapy and to characterize their production of extracellular proteins. STUDY DESIGN: Consecutive root canal samples (RCS) taken as bacteriological controls during root canal treatment of teeth with apical periodontitis were analyzed in a total of 100 clinical cases. Bacteria were isolated and classified by selective media and gas liquid chromatography. Streptococcal strains were identified by carbohydrate fermentation, hydrolysis of aesculin/arginine, and production of enzymes. Releases of extracellular proteins by streptococci and Enterococcus spp in fluid culture media were examined with SDS-PAGE and 2-dimension gel electrophoresis (2 DE). Extracellular proteins produced were quantified and qualitatively analyzed. Specific proteins were targeted with Western immunoblot assays. Comparisons were made with type strains. RESULTS: Of a total of 241 bacterial strains recovered in the first samples submitted, Streptococcus gordonii, S anginosus, and S oralis were the most frequently isolated streptococci. In 49 of 89 resubmitted samples showing bacterial growth, S gordonii and S oralis still predominated among streptococci. Other common bacterial isolates were Enterococcus spp, Lactobacillus paracasei, and Olsenella uli. Quantitative and qualitative differences in extracellular protein production were observed among clinical isolates and laboratory streptococcal strains. In similar conditions for growth, S intermedius, S anginosus, S oralis, and S gordonii were strong producers of extracellular proteins (>3.0 microg/mL), while Enterococcus spp and S mutans were weak. Whole cell protein extracts showed a different profile from that of extracellular proteins. The chaperone protein DnaK was recognized to be produced extracellularly by S gordonii, S oralis, S anginosus, and S parasanguis. CONCLUSIONS: Being strong producers of extracellular proteins and by virtue of common presence in teeth undergoing endodontic therapy, S gordonii, S anginosus, and S oralis may be of pathogenic significance in posttreatment apical periodontitis.
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