Ecology of the Oral Microbiome: Beyond Bacteria Baker, Jonathon L; Bor, Batbileg; Agnello, Melissa ...
Trends in microbiology (Regular ed.),
05/2017, Letnik:
25, Številka:
5
Journal Article
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Although great strides have been made in understanding the complex bacterial community inhabiting the human oral cavity, for a variety of (mainly technical) reasons the ecological contributions of ...oral fungi, viruses, phages, and the candidate phyla radiation (CPR) group of ultrasmall bacteria have remained understudied. Several recent reports have illustrated the diversity and importance of these organisms in the oral cavity, while TM7x and Candida albicans have served as crucial paradigms for CPR species and oral fungi, respectively. A comprehensive understanding of the oral microbiota and its influence on host health and disease will require a holistic view that emphasizes interactions among different residents within the oral community, as well as their interaction with the host.
Pseudomonas aeruginosa is a leading pathogen that has become increasingly resistant to the fluoroquinolone antibiotics due to widespread prescribing. Adverse outcomes have been shown for patients ...infected with fluoroquinolone-resistant strains. The type III secretion system (TTSS) is a major virulence determinant during acute infections through the injection of effector toxins into host cells. Most strains exhibit a unique TTSS virulence genotype defined by the presence of either exoS or exoU gene encoding two of the effector toxins, ExoS and ExoU, respectively. Specific TTSS effector genotype has been shown previously to differentially impact virulence in pneumonia. In this study, we examined the relationship between TTSS effector genotype and fluoroquinolone resistance mechanisms in a collection of 270 respiratory isolates. We found that a higher proportion of exoU+ strains were fluoroquinolone-resistant compared to exoS+ strains (63% vs 49%, p = 0.03) despite its lower overall prevalence (38% exoU+ vs 56% exoS+). Results from sequencing the quinolone resistance determining regions (QRDRs) of the 4 target genes (gyrA, gyrB, parC, parE) indicated that strains containing the exoU gene were more likely to acquire ≥ 2 mutations than exoS+ strains at MICs ≤ 8 µg/ml (13% vs none) and twice as likely to have mutations in both gyrA and parC than exoS+ strains (48% vs 24% p = 0.0439). Our findings indicate that P. aeruginosa strains differentially develop resistance-conferring mutations that correlate with TTSS effector genotype and the more virulent exoU+ subpopulation. Differences in mutational processes by virulence genotype that were observed suggest co-evolution of resistance and virulence traits favoring a more virulent genotype in the quinolone-rich clinical environment.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Candida albicans and Fusobacterium nucleatum are well-studied oral commensal microbes with pathogenic potential that are involved in various oral polymicrobial infectious diseases. Recently, we ...demonstrated that F. nucleatum ATCC 23726 coaggregates with C. albicans SN152, a process mainly mediated by fusobacterial membrane protein RadD and Candida cell wall protein Flo9. The aim of this study was to investigate the potential biological impact of this inter-kingdom interaction. We found that F. nucleatum ATCC 23726 inhibits growth and hyphal morphogenesis of C. albicans SN152 in a contact-dependent manner. Further analysis revealed that the inhibition of Candida hyphal morphogenesis is mediated via RadD and Flo9 protein pair. Using a murine macrophage cell line, we showed that the F. nucleatum-induced inhibition of Candida hyphal morphogenesis promotes C. albicans survival and negatively impacts the macrophage-killing capability of C. albicans. Furthermore, the yeast form of C. albicans repressed F. nucleatum-induced MCP-1 and TNFα production in macrophages. Our study suggests that the interaction between C. albicans and F. nucleatum leads to a mutual attenuation of virulence, which may function to promote a long-term commensal lifestyle within the oral cavity. This finding has significant implications for our understanding of inter-kingdom interaction and may impact clinical treatment strategies.
Diet modulates gut microbiota and plays an important role in human health. The aim of this study was to test the effect of a low-fat vegan diet on gut microbiota and its association with weight, body ...composition, and insulin resistance in overweight men and women. We enrolled 168 participants and randomly assigned them to a vegan (
= 84) or a control group (
= 84) for 16 weeks. Of these, 115 returned all gut microbiome samples. Gut microbiota composition was assessed using uBiome Explorer™ kits. Body composition was measured using dual energy X-ray absorptiometry. Insulin sensitivity was quantified with the predicted clamp-derived insulin sensitivity index from a standard meal test. Repeated measure ANOVA was used for statistical analysis. Body weight decreased in the vegan group (treatment effect -5.9 kg 95% CI, -7.0 to -4.9 kg;
< 0.001), mainly due to a reduction in fat mass (-3.9 kg 95% CI, -4.6 to -3.1 kg;
< 0.001) and in visceral fat (-240 cm
95% CI, -345 to -135 kg;
< 0.001). PREDIcted M, insulin sensitivity index (PREDIM) increased in the vegan group (treatment effect +0.83 95% CI, +0.48 to +1.2;
< 0.001). The relative abundance of Faecalibacterium prausnitzii increased in the vegan group (+5.1% 95% CI, +2.4 to +7.9%;
< 0.001) and correlated negatively with changes in weight (r = -0.24;
= 0.01), fat mass (r = -0.22;
= 0.02), and visceral fat (r = -0.20;
= 0.03). The relative abundance of Bacteroides fragilis decreased in both groups, but less in the vegan group, making the treatment effect positive (+18.9% 95% CI, +14.2 to +23.7%;
< 0.001), which correlated negatively with changes in weight (r = -0.44;
< 0.001), fat mass (r = -0.43;
< 0.001), and visceral fat (r = -0.28;
= 0.003) and positively with PREDIM (r = 0.36;
< 0.001), so a smaller reduction in Bacteroides fragilis was associated with a greater loss of body weight, fat mass, visceral fat, and a greater increase in insulin sensitivity. A low-fat vegan diet induced significant changes in gut microbiota, which were related to changes in weight, body composition, and insulin sensitivity in overweight adults, suggesting a potential use in clinical practice.
Fluoroquinolone (FQ) resistance is highly prevalent among clinical strains of
, limiting treatment options. We have reported previously that highly virulent strains containing the
gene of the type ...III secretion system are more likely to be FQ-resistant than strains containing the
gene, as well as more likely to acquire resistance-conferring mutations in
and
. We hypothesize that FQ-resistance imposes a lower fitness cost on
compared to
strains, thus allowing for better adaptation to the FQ-rich clinical environment. We created isogenic mutants containing a common FQ-resistance conferring point mutation in
from three
to three
clinical isolates and tested fitness
using head-to-head competition assays. The mutation differentially affected fitness in the
and
strains tested. While the addition of the
mutation dramatically increased fitness in one of the
strains leaving the other two unaffected, all three
strains displayed a general decrease in fitness. In addition, we found that
strains may be able to compensate for the fitness costs associated with the mutation through better regulation of supercoiling compared to the
strains. These results may provide a biological explanation for the observed predominance of the virulent
genotype in FQ-resistant clinical subpopulations and represent the first investigation into potential differences in fitness costs of FQ-resistance that are linked to the virulence genotype of
. Understanding the fitness costs of antibiotic resistance and possibilities of compensation for these costs is essential for the rational development of strategies to combat the problem of antibiotic resistance.
The anticariogenic activity of the extract of Glycyrrhiza uralensis (licorice) has been well documented. We recently developed an herbal lollipop containing licorice extracts with Glycyrrhizol A, the ...compound displaying strong antimicrobial activity against Streptococcus mutans. Preliminary testing showed that the herbal lollipop reduced salivary S. mutans counts in vivo. In this study, we aimed to further test the efficacy of this herbal lollipop for reducing salivary S. mutans levels, and investigate its impact on salivary microbiome. Using a well-established in vitro oral microbiome model, we showed that licorice extract displays targeted killing against S. mutans without affecting the biodiversity of the community. In vivo study corroborated in vitro findings, showing for high caries-risk children aged 3-6 with salivary S. mutans levels >5x105 cells/ml, daily use of 2 licorice-containing lollipops for 3 weeks significantly reduced salivary S. mutans levels compared to the control group. Salivary microbiome analysis showed either no change or even increase in phylogenetic diversity of the oral community following herbal lollipop usage. Although further study with longer term observation is needed, these results suggest that use of licorice extract-containing lollipops can be as a simple and effective way to reduce the risk of dental caries in children.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Dental caries remains the most common chronic disease in children, and the respective etiology is not fully understood. Though
is an important factor in the initiation and progression of caries, its ...presence is not always associated with the disease. The existence of caries discordant populations, in which
counts do not correlate with caries experience, poses a challenging problem. This study explored the possible correlation of S.
and other microorganism levels on caries-associated ecology of caries-concordant and discordant populations. A total of forty-seven children were analyzed in this study and stratified into four clinical groups based on their
levels in saliva (HS/LS: High/low
) and caries experience.
levels were determined by culture-based selective plating. The salivary microbiome of caries concordant and discordant populations was investigated by 16S rRNA gene sequencing and downstream bioinformatics analysis. The salivary microbial communities significantly clustered based on
levels and independent of their caries experience. In addition to
levels, significant differences in the abundance of other species were observed between HS and LS groups. Interestingly, disease-associated species such as
spp., and
spp. were significantly increased in HS groups and may contribute, in combination with
, to the caries progression. Furthermore, health-associated species exhibited higher abundance in the LS groups, such as
sp., and
spp. but their possible contribution to the caries process remains to be elucidated. This study provides evidence that
may play a role in shaping the salivary microbial community. Our results highlight that future caries research should consider additional species as health/disease microbial markers in conjunction with
to improve diagnosis and caries management of the caries-discordant population.
OBJECTIVES:To determine the differential association of host characteristics, antimicrobial resistance, and type III secretion system virulence of Pseudomonas aeruginosa isolates with respiratory ...syndromes in hospitalized adult patients.
DESIGN:Retrospective, cohort study.
SETTING:Community teaching hospital.
PATIENTS:Two hundred eighteen consecutive adult patients with respiratory culture positive for P. aeruginosa between January 2005 to January 2010.
INTERVENTIONS:Medical charts were reviewed to obtain demographic, laboratory, radiographic, and clinical information. Isolates were assayed by polymerase chain reaction for genes encoding the type III secretion system effectors (ExoU, ExoS, and PcrV) and for strain relatedness using randomly amplified polymorphic DNA analysis. Levofloxacin susceptibility was determined by broth microdilution. Patients were grouped by colonization, bronchitis, or pneumonia and were compared for differential risk of developing the clinical syndrome with respect to host and microbial characteristics.
MEASUREMENTS AND MAIN RESULTS:Half of the study cohort (54%, 117 of 218) had pneumonia, 32% (70 of 218) had bronchitis, and 14% (31 of 218) had colonization; in-hospital mortality was 35%, 11%, and 0%, respectively. Host factors strongly associated with pneumonia development were residence in long-term care facility, healthcare-associated acquisition of P. aeruginosa, higher Acute Physiology and Chronic Health Evaluation II score, presence of enteral feeding tube, mechanical ventilation, and recent history of pneumonia. Fluoroquinolone-resistant (57% vs 34%, 16%; p < 0.0001) and multidrug-resistant (36% vs 26%, 7%; p = 0.0045) strains were more likely to cause pneumonia than bronchitis or colonization, respectively. Analysis of host and microbial factors in a multivariate regression model yielded the combined traits of fluoroquinolone resistance and gene encoding the type III secretion system ExoU effector in P. aeruginosa as the single most significant predictor of pneumonia development.
CONCLUSIONS:These results suggest that fluoroquinolone-resistant phenotype in a type III secretion system exoU strain background contributes toward the pathogenesis of P. aeruginosa in pneumonia.
Halitosis refers to malodor emanating from the oral cavity. Several mouthrinses with halitosis-reduction exist on the market, but their effect on the oral microbiome is largely unknown. In this ...study, we used an efficient in vitro model system to investigate a test mouthrinse's impact on the oral microbiome.
Single halitosis-associated species and other common oral microorganism cultures were exposed to the test mouthrinse over time, and their viability was determined by culture-based selective plating. Next, the saliva-derived microbiome from healthy and halitosis-associated individuals was cultured in the presence of the test mouthrinse over time using the previously developed in vitro model system. The microbiome composition was assessed with 16S rRNA gene sequencing and downstream bioinformatics analyses.
The test mouthrinse displayed antimicrobial activity against known anaerobic bacterial species producing halitosis-related compounds such as Fusobacterium nucleatum, F. periodonticum, and Prevotella intermedia but not against other common oral microorganisms. In the multispecies, saliva-derived cultures, mouthrinse exposure decreased the relative abundance of the Fusobacterium and Prevotella genera while not affecting overall diversity.
The test mouthrinse had promising anti-halitosis characteristics at the microbiome level, as demonstrated by the reduction in the relative abundance of halitosis-associated taxa while maintaining microbial diversity.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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