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Journal of Alzheimer's Disease : JAD 2023Pre-clinical evidence implicates oral bacteria in the pathogenesis of Alzheimer's disease (AD), while clinical studies show diverse results. (Meta-Analysis)
Meta-Analysis
BACKGROUND
Pre-clinical evidence implicates oral bacteria in the pathogenesis of Alzheimer's disease (AD), while clinical studies show diverse results.
OBJECTIVE
To comprehensively assess the association between oral bacteria and AD with clinical evidence.
METHODS
Studies investigating the association between oral bacteria and AD were identified through a systematic search of six databases PubMed, Embase, Cochrane Central Library, Scopus, ScienceDirect, and Web of Science. Methodological quality ratings of the included studies were performed. A best evidence synthesis was employed to integrate the results. When applicable, a meta-analysis was conducted using a random-effect model.
RESULTS
Of the 16 studies included, ten investigated periodontal pathobionts and six were microbiome-wide association studies. Samples from the brain, serum, and oral cavity were tested. We found over a ten-fold and six-fold increased risk of AD when there were oral bacteria (OR = 10.68 95% CI: 4.48-25.43; p < 0.00001, I2 = 0%) and Porphyromonas gingivalis (OR = 6.84 95% CI: 2.70-17.31; p < 0.0001, I2 = 0%) respectively in the brain. While AD patients exhibited lower alpha diversity of oral microbiota than healthy controls, the findings of bacterial communities were inconsistent among studies. The best evidence synthesis suggested a moderate level of evidence for an overall association between oral bacteria and AD and for oral bacteria being a risk factor for AD.
CONCLUSION
Current evidence moderately supports the association between oral bacteria and AD, while the association was strong when oral bacteria were detectable in the brain. Further evidence is needed to clarify the interrelationship between both individual species and bacterial communities and the development of AD.
Topics: Humans; Alzheimer Disease; Cognitive Dysfunction; Risk Factors; Microbiota; Porphyromonas gingivalis
PubMed: 36404545
DOI: 10.3233/JAD-220627 -
CNS Neuroscience & Therapeutics Jan 2023Recent advances have highlighted the relationships between gut dysbiosis and Parkinson's disease (PD). Microbiota transplantation from PD patients to mice can induce... (Review)
Review
INTRODUCTION
Recent advances have highlighted the relationships between gut dysbiosis and Parkinson's disease (PD). Microbiota transplantation from PD patients to mice can induce increased alpha-synuclein-mediated motor deficits. Human studies have identified differences in the gut microbiota of PD patients compared to healthy controls. We undertook a systematic review to evaluate the available evidence for the involvement of gut bacteria in the etiology of PD.
METHODS
The PubMed databank, the China National Knowledge Infrastructure databank, and Wanfang Data were searched from inception until June 2021 to identify human case-control studies that investigated relationships between PD and microbiota quantified from feces. We evaluated the resulting studies focusing on bacterial taxa that were different between PD patients and healthy controls.
RESULTS
Twenty-six studies were found in which 53 microbial families and 98 genera exhibited differences between patients with PD and healthy controls. The genera identified by more than two studies as increased in PD were Bifidobacterium, Alistipes, Christensenella, Enterococcus, Oscillospira, Bilophila, Desulfovibrio, Escherichia/Shigella, and Akkermansia, while Prevotella, Blautia, Faecalibacterium, Fusicatenibacter, and Haemophilus had three or more reports of being lower in PD patients. More than one report demonstrated that Bacteroides, Odoribacter, Parabacteroides, Butyricicoccus, Butyrivibrio, Clostridium, Coprococcus, Lachnospira, Lactobacillus, Megasphaera, Phascolarctobacterium, Roseburia, Ruminococcus, Streptococcus, and Klebsiella were altered in both directions.
CONCLUSION
Our review shows that the involvement of the gut microbiome in the etiology of PD may involve alterations of short-chain fatty acids (SCFAs)-producing bacteria and an increase in putative gut pathobionts. SCFAs-producing bacteria may vary above or below an "optimal range," causing imbalances. Considering that Bifidobacterium, Lactobacillus, and Akkermansia are beneficial for human health, increased Bifidobacterium and Lactobacillus in the PD gut microbiome may be associated with PD medications, especially COMT inhibitors, while a high level of Akkermansia may be associated with aging.
Topics: Humans; Animals; Mice; Parkinson Disease; Gastrointestinal Microbiome; Bacteria; Feces; Fatty Acids, Volatile
PubMed: 36284437
DOI: 10.1111/cns.13990 -
Andrology Jan 2021Male factor is attributable in up to 50% of cases of infertility. In vitro studies demonstrate that bacteria can negatively impact sperm function. The use of... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Male factor is attributable in up to 50% of cases of infertility. In vitro studies demonstrate that bacteria can negatively impact sperm function. The use of next-generation sequencing techniques has provided a better understanding of the human microbiome, and dysbiosis has been reported to impact health. Evidence regarding the impact of the semen microbiome on sperm function and fertility remains conflicting.
MATERIALS AND METHODS
A systematic search was conducted in accordance with the Preferred Reporting Items for Reviews and Meta-analysis (PRISMA) statement. The databases MEDLINE, OVID and PubMed were searched to identify English language studies related to the identification of bacteria in the semen of infertile and fertile men, between 1992 and 2019. Fifty-five observational studies were included, with 51 299 subjects. We included studies identifying bacteria using next-generation sequencing, culture or polymerase chain reaction.
RESULTS
The semen microbiome was rich and diverse in both fertile and infertile men. Three NGS studies reported clustering of the seminal microbiome with a predominant species. Lactobacillus and Prevotella were dominant in respective clusters. Lactobacillus was associated with improvements in semen parameters. Prevotella appeared to exert a negative effect on sperm quality. Bacteriospermia negatively impacted sperm concentration and progressive motility, and DNA fragmentation index (DFI; MD: 3.518, 95% CI: 0.907 to 6.129, P = .008). There was an increased prevalence of ureaplasma urealyticum in infertile men (OR: 2.25, 95% CI: 1.47-3.46). Ureaplasma urealyticum negatively impacted concentration and morphology. There was no difference in the prevalence of chlamydia trachomatis between fertile and infertile men and no significant impact on semen parameters. Enterococcus faecalis negatively impacted total motility, and Mycoplasma hominis negatively impacted concentration, PM and morphology.
DISCUSSION AND CONCLUSIONS
Ureaplasma urealyticum, Enterococcus faecalis, Mycoplasma hominis and Prevotella negatively impact semen parameters, whereas Lactobacillus appears to protect sperm quality. These findings may facilitate the development of novel therapies (eg probiotics), although the evidence regarding the impact of the seminal microbiome on fertility is inconclusive and further studies are needed to investigate this association.
Topics: Fertility; Humans; Infertility, Male; Male; Microbiota; Semen; Spermatozoa
PubMed: 32794312
DOI: 10.1111/andr.12886 -
International Journal of Molecular... Nov 2022There is a growing body of evidence highlighting there are significant changes in the gut microbiota composition and relative abundance in various neurological... (Review)
Review
There is a growing body of evidence highlighting there are significant changes in the gut microbiota composition and relative abundance in various neurological disorders. We performed a systematic review of the different microbiota altered in a wide range of neurological disorders (Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis, and stroke). Fifty-two studies were included representing 5496 patients. At the genus level, the most frequently involved microbiota are Akkermansia, Faecalibacterium, and Prevotella. The overlap between the pathologies was strongest for MS and PD, sharing eight genera (Akkermansia, Butyricicoccus, Bifidobacterium, Coprococcus, Dorea, Faecalibacterium, Parabacteroides, and Prevotella) and PD and stroke, sharing six genera (Enterococcus, Faecalibacterium, Lactobacillus, Parabacteroides, Prevotella, and Roseburia). The identification signatures overlapping for AD, PD, and MS raise the question of whether these reflect a common etiology or rather common consequence of these diseases. The interpretation is hampered by the low number and low power for AD, ALS, and stroke with ample opportunity for false positive and false negative findings.
Topics: Humans; Gastrointestinal Microbiome; Nervous System Diseases; Parkinson Disease; Microbiota; Akkermansia; Multiple Sclerosis; Prevotella; Clostridiaceae; Clostridiales; Stroke
PubMed: 36430144
DOI: 10.3390/ijms232213665 -
International Journal of Infectious... Dec 2022To describe the global trends of pulmonary nontuberculous mycobacteria (NTM) infection and disease. (Review)
Review
OBJECTIVES
To describe the global trends of pulmonary nontuberculous mycobacteria (NTM) infection and disease.
METHODS
A systematic review of studies including culture-based NTM data over time. Studies reporting on pulmonary NTM infection and/or disease were included. Information on the use of guideline-based criteria for disease were collected, in which, infection is defined as the absence of symptoms and radiological findings compatible with NTM pulmonary disease. The trends of change for incidence/prevalence were evaluated using linear regressions, and the corresponding pooled estimates were calculated.
RESULTS
Most studies reported increasing pulmonary NTM infection (82.1%) and disease (66.7%) trends. The overall annual rate of change for NTM infection and disease per 100,000 persons/year was 4.0% (95% confidence interval [CI]: 3.2-4.8) and 4.1% (95% CI: 3.2-5.0), respectively. For absolute numbers of NTM infection and disease, the overall annual change was 2.0 (95% CI: 1.6-2.3) and 0.5 (95% CI: 0.3-0.7), respectively. An increasing trend was also seen for Mycobacterium avium complex infection (n = 15/19, 78.9%) and disease (n = 10/12, 83.9%) and for Mycobacterium abscessus complex (n = 15/23, 65.2%) infection (n = 11/17, 64.7%) but less so for disease (n = 2/8, 25.0%).
CONCLUSION
Our data indicate an overall increase in NTM worldwide for both infection and disease. The explanation to this phenomenon warrants further investigation.
Topics: Humans; Nontuberculous Mycobacteria; Mycobacterium Infections, Nontuberculous; Mycobacterium avium Complex; Mycobacterium avium-intracellulare Infection; Mycobacterium abscessus; Lung Diseases; Pneumonia
PubMed: 36244600
DOI: 10.1016/j.ijid.2022.10.013 -
BJOG : An International Journal of... Jan 2020Persistent infection with high-risk human papillomavirus can lead to cervical dysplasia and cancer. Recent studies have suggested associations between the composition of...
BACKGROUND
Persistent infection with high-risk human papillomavirus can lead to cervical dysplasia and cancer. Recent studies have suggested associations between the composition of the vaginal microbiota, infection with human papillomavirus (HPV) and progression to cervical dysplasia and cancer.
OBJECTIVE
To assess how specific cervico-vaginal microbiota compositions are associated with HPV infection, cervical dysplasia and cancer, we conducted a systematic review and network meta-analysis (registered in PROSPERO: CRD42018112862).
SEARCH STRATEGY
PubMed, Web of science, Embase and Cochrane database.
SELECTION CRITERIA
All original studies describing at least two community state types of bacteria (CST), based on molecular techniques enabling identification of bacteria, and reporting the association with HPV infection, cervical dysplasia and/or cervical cancer.
DATA COLLECTION AND ANALYSIS
For the meta-analysis, a network map was constructed to provide an overview of the network relationships and to assess how many studies provided direct evidence for the different vaginal microbiota compositions and HPV, cervical dysplasia or cancer. Thereafter, the consistency of the model was assessed, and forest plots were constructed to pool and summarise the available evidence, presenting odds ratios and 95% confidence intervals.
MAIN RESULTS
Vaginal microbiota dominated by non-Lactobacilli species or Lactobacillus iners were associated with three to five times higher odds of any prevalent HPV and two to three times higher for high-risk HPV and dysplasia/cervical cancer compared with Lactobacillus crispatus.
CONCLUSIONS
These findings suggest an association between certain bacterial community types of the vaginal microbiota and HPV infection and HPV-related disease. This may be useful for guiding treatment options or serve as biomarkers for HPV-related disease.
TWEETABLE ABSTRACT
This network meta-analysis suggests an association between different vaginal bacterial community types and the risk of HPV.
Topics: Female; Humans; Lactobacillus; Microbiota; Network Meta-Analysis; Papillomaviridae; Papillomavirus Infections; RNA, Ribosomal, 16S; Uterine Cervical Neoplasms; Vagina; Uterine Cervical Dysplasia
PubMed: 31237400
DOI: 10.1111/1471-0528.15854 -
Oral Diseases Jan 2023Periodontitis is a chronic non-communicable disease caused by a dysbiotic microbiota. Pathogens can spread to the bloodstream, colonize other tissues or organs, and... (Review)
Review
Periodontitis is a chronic non-communicable disease caused by a dysbiotic microbiota. Pathogens can spread to the bloodstream, colonize other tissues or organs, and favor the onset of other pathologies, such as Alzheimer's disease (AD). Pathogens could permanently or transiently colonize the brain and induce an immune response. Thus, we analyzed the evidence combining oral bacteria's detection in the brain, both in animals and humans affected with AD. This systematic review was carried out following the PRISMA guideline. Studies that detected oral bacteria at the brain level were selected. The search was carried out in the Medline, Latindex, SciELO, and Cochrane Library databases. SYRCLE tool and Newcastle-Ottawa Scale were used for the risk of bias assessment. 23 studies were selected according to the eligibility criteria. Infection with oral pathogens in animals was related to developing neuropathological characteristics of AD and bacteria detection in the brain. In patients with AD, oral bacteria were detected in brain tissues, and increased levels of pro-inflammatory cytokines were also detected. There is evidence of a microbiological susceptibility to develop AD when the most dysbiosis-associated oral bacteria are present. The presence of bacteria in the brain is related to AD's pathological characteristics, suggesting an etiological oral-brain axis.
Topics: Animals; Humans; Alzheimer Disease; Periodontitis; Bacteria; Microbiota; Brain; Dysbiosis
PubMed: 34698406
DOI: 10.1111/odi.14054 -
Experimental Dermatology Oct 2021Seborrheic dermatitis (SD) and dandruff (DF) are common chronic inflammatory skin diseases characterized by recurrent greasy scales, sometimes with erythema and...
Seborrheic dermatitis (SD) and dandruff (DF) are common chronic inflammatory skin diseases characterized by recurrent greasy scales, sometimes with erythema and itchiness. Although the exact pathophysiology of the disease is still unclear, current theories highlight the role of microbes on the skin surface in the pathogenesis of SD. Here, we conducted a systematic review to investigate the skin microbiome alterations in patients with SD/DF. We searched Medline/PubMed, Embase and Web of Science for research studies published in English between 1 January 2000 and 31 December 2020. A total of 12 studies with 706 SD/DF samples and 379 healthy samples were included in this study. The scalp and face were predominated by the fungi of Ascomycota and Basidiomycota and the bacteria of Actinobacteria and Firmicutes. In general, the included studies demonstrated an increased Malassezia restricta/Malassezia globosa ratio and a reduction in the Cutibaterium/Staphylococcus ratio in the setting of SD/DF. Staphylococcus was associated with epidermal barrier damage, including elevated levels of trans-epidermal water loss and pH, while Cutibacterium had a positive correlation with water content. Malassezia was also found to be related to an increased itching score and disease severity. Further studies focusing on the interactions between various microbes and the host and microbes can help us to better understand the pathogenesis of SD/DF.
Topics: Dandruff; Dermatitis, Seborrheic; Humans; Microbiota; Skin
PubMed: 34415635
DOI: 10.1111/exd.14450 -
International Journal of Molecular... Apr 2022Bacteriophages offer an alternative for the treatment of multidrug-resistant bacterial diseases as their mechanism of action differs from that of antibiotics. However,... (Review)
Review
Bacteriophages offer an alternative for the treatment of multidrug-resistant bacterial diseases as their mechanism of action differs from that of antibiotics. However, their application in the clinical field is limited to specific cases of patients with few or no other alternative therapies. This systematic review assesses the effectiveness and safety of phage therapy against multidrug-resistant bacteria through the evaluation of studies published over the past decade. To that end, a bibliographic search was carried out in the PubMed, Science Direct, and Google Scholar databases. Of the 1500 studies found, 27 met the inclusion criteria, with a total of 165 treated patients. Treatment effectiveness, defined as the reduction in or elimination of the bacterial load, was 85%. Except for two patients who died from causes unrelated to phage therapy, no serious adverse events were reported. This shows that phage therapy could be an alternative treatment for patients with infections associated with multidrug-resistant bacteria. However, owing to the phage specificity required for the treatment of various bacterial strains, this therapy must be personalized in terms of bacteriophage type, route of administration, and dosage.
Topics: Anti-Bacterial Agents; Bacteria; Bacterial Infections; Bacteriophages; Drug Resistance, Multiple, Bacterial; Humans; Phage Therapy
PubMed: 35562968
DOI: 10.3390/ijms23094577 -
The Journal of Infection Aug 2020In previous influenza pandemics, bacterial co-infections have been a major cause of mortality. We aimed to evaluate the burden of co-infections in patients with COVID-19. (Meta-Analysis)
Meta-Analysis
OBJECTIVES
In previous influenza pandemics, bacterial co-infections have been a major cause of mortality. We aimed to evaluate the burden of co-infections in patients with COVID-19.
METHODS
We systematically searched Embase, Medline, Cochrane Library, LILACS and CINAHL for eligible studies published from 1 January 2020 to 17 April 2020. We included patients of all ages, in all settings. The main outcome was the proportion of patients with a bacterial, fungal or viral co-infection. .
RESULTS
Thirty studies including 3834 patients were included. Overall, 7% of hospitalised COVID-19 patients had a bacterial co-infection (95% CI 3-12%, n=2183, I=92·2%). A higher proportion of ICU patients had bacterial co-infections than patients in mixed ward/ICU settings (14%, 95% CI 5-26, I=74·7% versus 4%, 95% CI 1-9, I= 91·7%). The commonest bacteria were Mycoplasma pneumonia, Pseudomonas aeruginosa and Haemophilus influenzae. The pooled proportion with a viral co-infection was 3% (95% CI 1-6, n=1014, I=62·3%), with Respiratory Syncytial Virus and influenza A the commonest. Three studies reported fungal co-infections.
CONCLUSIONS
A low proportion of COVID-19 patients have a bacterial co-infection; less than in previous influenza pandemics. These findings do not support the routine use of antibiotics in the management of confirmed COVID-19 infection.
Topics: Bacterial Infections; Betacoronavirus; COVID-19; Coinfection; Coronavirus Infections; Humans; Mycoses; Pandemics; Pneumonia, Viral; SARS-CoV-2; Virus Diseases
PubMed: 32473235
DOI: 10.1016/j.jinf.2020.05.046