Influence of abiotic factors on the bacteriocinogenic activity of Actinobacillus actinomycetemcomitans

Partial Characterization of Novel Bacteriocin SF1 Produced by Shigella flexneri and Their Lethal Activity on Members of Gut Microbiota

A strain of Shigella flexneri producing bacteriocin was isolated from a patient with diarrhea. The main objective of this study was to isolate and partially characterize the bacteriocin. The producing microorganism was identified using biochemical, serological, and molecular methods. The lethal activity of the S. flexneri strain was studied using the drop method. This bacterial strain showed activity against different strains of E. coli and B. fragilis. Using immunological techniques, it was determined that S. flexneri belongs to serotype 2a, and by PCR, the presence of the ipaH plasmid was determined. By chromatographic techniques, it was determined that the bacteriocin is a peptide of high purity with a molecular weight of 66294.094 Da. The amino acid composition and sequence were determined by the Edman reaction, and a sequence of 619 amino acid residues was obtained. Only in five positions of this sequence, the amino acid glutamine changed to glutamic acid with respect to colicin U produced by S. boydii. From an ecological point of view, it could be assumed that SF1 bacteriocin contributes to eliminate some members of the normal microbiota of the human intestine, facilitating colonization and then producing the invasion process that characterizes the pathogenicity of Shigella.

Do probiotics offer opportunities to manipulate the periodontal oral microbiota?

BACKGROUND

As in other fields of healthcare, probiotics have been introduced for prevention and treatment of periodontal diseases.

OBJECTIVE

This review was initiated to explore whether the use of probiotics can influence the periodontal microbiota and periodontal health.

MATERIALS AND METHODS

Literature on the mode of action of oral probiotics was reviewed and a systematic review was performed on the microbiological and clinical effects of oral probiotics on periodontal health.

RESULTS

Three animal and 11 in vivo human studies were retrieved. Six studies reported on microbiological effects whereas eight studies report on clinical effects. Seven studies were performed on healthy or gingivitis patients and four studies on periodontitis patients. Many of the retrieved studies are pilot in nature and with low quality. The high degree of heterogeneity between studies hampered analysis.

CONCLUSION

Taking into consideration all limitations, the currently available data indicate an effect of probiotics on the oral microbiota and a more limited effect on clinical periodontal outcome measures. However, there is an urgent need for properly conducted clinical trials where probiotics are used as adjuncts to standard periodontal care, similar to antibiotics, using probiotic strains with, at least at an in vitro level, proven periodontal probiotic effects.

Antagonism and synergism in Gardnerella vaginalis strains isolated from women with bacterial vaginosis

Antagonistic and synergistic substances are important for interactions between micro-organisms associated with human body surfaces, either in healthy or in diseased conditions. In the present study, such compounds produced by Gardnerella vaginalis strains isolated from women with bacterial vaginosis (BV) were detected in vitro and the antagonistic ones were partially characterized. Among 11 G. vaginalis strains tested, all showed antagonistic activity against at least one of the 22 indicator bacteria assayed. Interestingly, for some of these strains, antagonism reverted to synergism, favouring one of the indicator strains (Peptostreptococcus anaerobius) when the growth medium was changed. Partial characterization of antagonistic substances suggested a bacteriocin-like chemical nature. Depending on growth conditions, G. vaginalis isolated from women with BV produced antagonistic or synergistic compounds for other bacterial components of the vaginal ecosystem. This is the first report to our knowledge of the production of antagonistic and/or synergistic substances by G. vaginalis. This ability may be a pivotal factor in understanding BV and the ecological role of this bacterium in the vaginal environment.

Bacteriocin production by Shigella sonnei isolated from faeces of children with acute diarrhoea

Shigella is a common agent of diarrhoea, a worldwide major health problem. The bacterium produces bacteriocins; however, the role of these substances as a virulence factor is completely unknown. With the aim to search for colicin production by Shigella sonnei, to evaluate the influence of culture conditions on bacteriocin expression, and to characterize the substance partially, 16 S. sonnei strains isolated from children with diarrhoea were tested for antagonism against members of the intestinal microbiota or agents of diarrhoea. Nine strains exhibited isoantagonism and heteroantagonism against S. flexneri and diarrhoeagenic Escherichia coli. Autoantagonism and antagonism against the intestinal microbiota were not detected. Culture medium and incubation conditions influenced antagonism expression. Antagonism resulting from bacteriophages, low pH, fatty acids, hydrogen peroxide, and chloroform was excluded. The activity of the intracellular fraction obtained with 75% ammonium sulphate was preserved at pH 1.0-11.0, and was found to be reduced by organic solvents and affected by high temperatures and proteases. The antagonistic spectrum and the in vitro conditions for better antagonism expression suggest that the role of colicin in S. sonnei virulence, if any, would be expressed prior to infection, and may regulate population density of enteropathogens by helping in organism transmission.

Production of antagonistic substance by Eikenella corrodens isolated from the oral cavity of human beings with and without periodontal disease

AIMS

Antagonistic abilities may confer ecological advantages for micro-organisms in competitive ecosystems. However, reports regarding this phenomenon in Eikenella corrodens are not available.

METHODS AND RESULTS

Nineteen E. corrodens strains, isolated from the oral cavity of human beings without periodontal disease (n = 5) and with aggressive (n = 9) and chronic (n = 5) periodontitis, as well as a reference strain (E. corrodens ATCC23834), were evaluated for antagonistic activity. The following indicators were used: Porphyromonas gingivalis FDC381, Prevotella intermedia ATCC25611, Actinomyces israelii ATCC12102, Eubacterium lentum ATCC25559, Peptostreptococcus anaerobius ATCC27337, Actinobacillus actinomycetemcomitans FDCY4, Fusobacterium nucleatum ATCC10953, Streptococcus sanguinis ATCC10557, Streptococcus uberis ATCC9927, Streptococcus mutans IM/UFRJ, Staphylococcus aureus ATCC33591 and Candida albicans ATCC18804. All the strains showed antagonism against at least one of the indicator strains. This phenomenon was more frequently observed for strains isolated from patients with chronic periodontitis (36.4%), than those from healthy subjects (20.6%) and those with aggressive periodontitis (10.8%).

CONCLUSIONS

The heterogeneous antagonistic spectrum exhibited by E. corrodens isolates suggests their ability to produce more than one antagonistic substance, whose ecological relevance is yet to be demonstrated.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first description of antagonistic compound production by E. corrodens and its relationships with the clinical status of the patients.