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- Hedberg, Maria, et al.
(author)
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Growth inhibition of Porphyromonas gingivalis biofilm by lactobacilli
- 2007
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Reports (other academic/artistic)abstract
- Background. Chronic periodontitis is one of the most common infectious diseases of the oral cavity. Dental plaque contains a mix of oral bacteria, and grows as biofilm on tooth surfaces. One of the bacterial species associated with periodontitis is Porphyromonas gingivalis, a Gram-negative anaerobic rod. Lactobacilli are used in probiotic products and are known to play an important role in the management of health by stimulating the immune system and contributing to the balance of the normal microflora. The knowledge of probiotic effects on oral bacteria is at present limited. Purpose. Lactobacillus reuteri, and Lactobacillus acidophilus are two species used in different probiotic products. In the presence of glycerol L. reuteri produces an antimicrobial product, 3-hydroxypropionaldehyd, also called reuterin. The purpose of the study was to examine the impact of L. reuteri and L. acidophilus on biofilm formed by P. gingivalis. Methods. To study whether L. reuteri and L. acidophilus had ability to alter the biofilm formation of P. gingivalis, 108 CFU/mL P. gingivalis and 108 CFU/mL of one of the lactobacilli were co-cultured in Brucella broth using cell-culture plates. After 48 h incubation the broth was removed and the biofilm studied by microscopy, crystal violet staining with subsequent absorbance measurements at 590 nm. Viable bacterial cells were determined in the biofilm and in the removed growth medium. Results. P. gingivalis and L. reuteri cultured individually formed heavy layers of biofilm (A590=2.1-3.1), whereas L. acidophilus gave a very thin layer (A590=0.21-0.35). In the biofilm competition assay, the level of viable P. gingivalis cells were reduced by at least 3 logs regardless the addition of glycerol when co-cultured with L. reuteri or L. acidophilus. In presence of glycerol, both P. gingivalis and L. reuteri were reduced below the detection level after 48 h incubation. Even though P. gingivalis cultured as single species formed a dense biofilm this was strongly reduced when co-cultured with L. acidophilus. Conclusion. In summary, the observed glycerol-dependent growth inhibition of P. gingivalis by L. reuteri seemed to be due to reuterin production. Competition in the biofilm model appeared to favor both lactobacillus species tested at the expense of P. gingivalis. The lactobacilli were able to strongly inhibit or suppress the growth of a major periodontal pathogen in the biofilm-competition assay.
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| 2. |
- Hedberg, Maria, et al.
(author)
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In-vitro growth inhibition of periodontitis-associated species by Lactobacillus reuteri
- 2006
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Reports (other academic/artistic)abstract
- Purpose. Lactobacillus reuteri, a species used in probiotic products, produces in vitro a bacteriocin, reuterin, in the presence of glycerol. The purpose of the study was to investigate in vitro whether L. reuteri strains inhibit the growth of periodontal pathogens. Methods. The inhibition study was based on a disk-diffusion method. The periodontitis-associated bacteria were pre-grown for 20 h in Brucella broth or Brucella blood agar at 37oC in anaerobic atmosphere. Standardization of bacterial inocula used in the assay was made by determinations of optical density, microscopic counting of cells, and viable count. Brucella blood agar plates, without or with glycerol (100 mM), were seeded with standardized inocula of the periodontal pathogens Fusobacterium nucleatum (IDH 4186), Porphyromonas gingivalis (ATCC 33277), Prevotella intermedia (ATCC 25611), and Actinobacillus actinomycetemcomitans (SA 1398). The lactobacilli L. reuteri ATCC 55730 and L. reuteri PTA 5289 were grown for 16 h in MRS broth. A 20-L aliquot of the suspension containing 107 CFU/mL was used to soak 6-mm paper disks, which were placed on Brucella agar plates (diameter 14 cm), seeded with each periodontal pathogen separately. The plates were then incubated for 3 - 7 days in anaerobic atmosphere at 37oC before measuring the inhibition zones. Results. On Brucella blood agar plates seeded with periodontal pathogens, no inhibition zones were seen around the paper discs. When glycerol was added to the agar, zones of 26 to 118 mm appeared. Sizes of the zones depended on the L. reuteri strain, the periodontal pathogen, and the sizes of their inocula. L. reuteri PTA 5289 had a stronger (7-30%) inhibitory effect than L. reuteri ATCC 55730 on all periodontal species. P. gingivalis was the most susceptible species among the tested strains. Conclusion. Both L. reuteri strains strongly inhibited or suppressed the growth of the tested periodontitis-associated bacteria in the presence of glycerol. The inhibitory activity of L. reuteri PTA 5289 was consistently higher than that of L. reuteri ATCC 55730. The results suggest that the inhibition activity of the tested lactobacilli was related to reuterin.
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| 4. |
- Sóki, József, et al.
(author)
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Description of Bacteroides strains showing hetero-resistance to cefoxitin and carbapenems
- 2008
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Reports (other academic/artistic)abstract
- Objective: Our aim was to document and characterize the hetero-resistant phenotypes, also known for methicillin and vancomycin-resistant Staphylococcus aureus and penicillin-resistant Streptococcus pneumoniae, of Bacteroides strains to cefoxitin and carbapenems noticed using Etests for antimicrobial susceptibility testing.Methods: Eight hetero-resistant B. fragilis strains collected during our 10 years experience and 100 clinical B. fragilis group strains recently isolated in Hungary were studied. For in vitro susceptibility measurements of cefoxitin and carbapenems agar dilution and Etest were used. Heteroresistant colonies growing in the ellipse between the E-test strip and main population were further analyzed. The occurrence of cfxA and cfiA resistance genes and their regulatory regions were investigated by PCR and nucleotide sequencing. Population analysis profiles were also investigated.Results: We detected 8 B. fragilis strains hetero-resistant to carbapenems using Etest susceptibility measurements (from 0.25-4 µg/ml of continous growth up to 16-32 µg/ml). All of them were cfiA-positive but did not harbour insertion sequence elements in the upstream region of the resistance genes. Of 100 recently isolated Bacteroides strains, 21 strains hetero-resistant to cefoxitin were observed. Their Etest patterns usually displayed a continuous growth of the less susceptible subpopulation from 8-128 µg/ml up to 256 µg/ml. Of these 21 isolates 11 harbored cfxA genes and their upstream regions were usually altered to the common 1.2 kb fragment, as seen in our previous studies. The population profile analysis demonstrated presence of more resistant subpopulations in the culture of strains corresponding to the more resistant colonies in the Etest ellipse zones. Repeated experiments of subcultures from single colonies taken from the heteroresistant zones resulted in the original hetero-resistant appearance using the Etest method.Conclusion: Hetero-resistance to important β-lactam antibiotics appear among Bacteroides strains but the phenotype could not yet be linked to any particular genetic constitution.This study was supported by a Hungarian National Research Fund grant (K69044).
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