URL: http://www.clinicaltrials.gov. Unique identifier: NCT01994720.

AimAlveolar resorption is one of the most important events in periodontitis. Osteoclast activity is regulated by the ratio between receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG). The aim of this study was to evaluate changes in the RANKL/OPG ratio in crevicular fluid after periodontal treatment. Material and methodsA total of 15 patients with periodontitis were included in the study group. Samples were collected from an area with active periodontitis and a healthy area. The RANKL and OPG levels were measured before and after periodontal scaling and root planing (SRP) treatment. The study group was compared to the control group, which included 10 patients without periodontitis. ID Clinicaltrial.gov: NCT03787875. ResultsA decrease in the RANKL level was found in areas with active periodontitis after periodontal treatment, but no change in the OPG level was observed.Therefore, the treatment induced a decrease in the RANKL/OPG ratio in sites with destructive periodontal activity. ConclusionsPeriodontal treatment acts on the RANKL/OPG ratio by decreasing osteoclastogenesis. These results encourage the use of these molecules for periodontal diagnosis, monitoring and treatment.

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Background. Sequencing variable regions of the 16S rRNA gene (≃300bp) with Illumina technology is commonly used to study the composition of human microbiota. Unfortunately, short reads are unable to differentiate between highly similar species. Considering that species from the same genus can be associated with health or disease it is important to identify them at the lowest possible taxonomic rank. Third-generation sequencing platforms such as PacBio SMRT, increase read lengths allowing to sequence the whole gene with the maximum taxonomic resolution. Despite its potential, full length 16S rRNA gene sequencing is not widely used yet. The aim of the current study was to compare the sequencing output and taxonomic annotation performance of the two approaches (Illumina short read sequencing and PacBio long read sequencing of 16S rRNA gene) in different human microbiome samples. Results. DNA from saliva, oral biofilms and faeces of 9 volunteers was isolated. Regions V3-V4 and V1-V9 were amplified and sequenced by Illumina Miseq and by PacBio Sequel II sequencers, respectively. With both platforms, a similar percentage of reads was assigned to the genus level (94.79% and 95.06% respectively) but with PacBio a higher proportion of reads were further assigned to the species level (55.23% vs 74.14%). Regarding overall bacterial composition, samples clustered by niche and not by sequencing platform. In addition, all genera with > 0.1% abundance were detected in both platforms for all types of samples. Although some genera such as Streptococcus tended to be observed at higher frequency in PacBio than in Illumina (20.14% vs 14.12% in saliva, 10.63% vs 6.59% in biofilm samples) none of the differences were statistically significant when correcting for multiple testing. Conclusions. The results presented in the current manuscript suggest that samples sequenced using Illumina and PacBio are mostly comparable. Considering that PacBio reads were assigned at the species level with higher accuracy than Illumina, our data support the use of PacBio technology for future microbiome studies, although a higher cost is currently required to obtain an equivalent number of reads per sample.

Infectious endocarditis (IE) by Bartonella species is an emerging problem worldwide. We report two cases of native valve Bartonella-associated IE events, both affecting adult male patients with a history of alcohol abuse and a low socioeconomic status. Admissions were due to pancytopenia and bleeding in one case and embolic stroke in the other. Blood cultures were negative and IgG indirect immunofluorescence assays (IFA) were positive for B. henselae/B. quintana in high titers (1/16,384-1/16,384, and 1/32,768-1/16,384, respectively). Cases were classified as definitive IE events according to modified Duke criteria due to the presence of valve vegetations with at least three minor criteria. One patient required aortic mechanical valve replacement and survived, and the other died after a massive hemorrhagic transformation of his stroke. PCR amplification and sequencing of the 16S ribosomal bacterial DNA from a valve tissue sample obtained at surgery in the patient who survived, confirmed B. quintana as the etiological agent. Bartonella-associated IE is an emerging problem in Chile, present in disadvantaged populations. It should be suspected in patients with culture-negative IE. IFA does not discriminate between B. henselae and B. quintana infection, but high titers suggest IE. Complementary PCR techniques may help to elucidate the final causative agent.