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Risk factors – Treatable traits
Published in Vibeke Backer, Peter G. Gibson, Ian D. Pavord, The Asthmas, 2023
Vibeke Backer, Peter G. Gibson, Ian D. Pavord
The area of respiratory infection undergoes a major information surge as modern molecular methods are applied to pathogen detection. There have been significant advances in the detection of individual pathogens through the use of PCR-based methods that are now applied in clinical practice, especially around respiratory viral detection. In addition, metagenomics has allowed recognition of multiple bacterial organisms at the taxa/phyla levels and is contributing to the understanding of disease pathogenesis. In patients with asthma who were not using inhaled corticosteroids, direct airway sampling identified that eosinophilic airway inflammation was associated with an altered airway microbiome. In severe asthma, patients with neutrophilic asthma have a greater frequency of pathogenic taxa at high relative abundance and reduced Streptococcus, Gemella and Porphyromonas taxa relative abundance.
Commensal Flora
Published in Firza Alexander Gronthoud, Practical Clinical Microbiology and Infectious Diseases, 2020
The commensal flora in the oropharynx consists mainly of anaerobes and streptococci. Coliforms can be transient colonizers, mainly in hospitalized patients. The most common anaerobes are Actinomyces, Bacteroides, Prevotella, Fusobacterium, Corynebacterium, Veillonella, Rothia and Capnocytophaga. Other members of the commensal flora are streptococci, Gemella and Granulicatella, Neisseria spp. and Haemophilus spp. Infections with oropharyngeal flora are seen in periodontal diseases, endocarditis and aspiration pneumonia. Oropharyngeal flora associated with endocarditis are viridans streptococci, Haemophilus spp. and members belonging to the HACEK group. Periodontal infections, perioral abscesses, sinusitis and mastoiditis may involve predominantly P. melaninogenica, Fusobacterium spp. and Peptostreptococcus spp. Aspiration of saliva may result in necrotizing pneumonia, lung abscess and empyema. Streptococcus mutans plays a particularly important role in dental plaques and caries. Eikenella corrodens is an important pathogen in human bites.
Composition and Diversity of Human Oral Microbiome
Published in Chaminda Jayampath Seneviratne, Microbial Biofilms, 2017
Preethi Balan, Chaminda Jayampath Seneviratne and Wim Crielaard
In one of the earliest studies on the human oral microbiome, Aas and colleagues analysed nine oral sites from five clinically healthy subjects to determine the site and subject specificity of bacterial colonisation using ABI 3100 DNA sequencer [10]. The species that were found to be common to all oral sites belonged to the genera Streptococcus, Veillonella, Gemella, and Granulicatella. However, some species were site specific. The predominant species on the tooth surface were Streptococcus sp. clone EK048, S. sanguinis, and S. gordonii, and Rothia dentocariosa, G. hemolysans, G. adiacens, Actinomyces sp. clone BL008 and Abiotrophia defectiva. In subgingival plaque, several species of Streptococcus and Gemella were often detected. S. mitis biovar 2 was present at the lateral side of the tongue while being absent on the tongue dorsum. On the hard palate, the predominant bacterial species included S. mitis, S. mitis biovar 2, Streptococcus sp. clone FN051, Streptococcus infantis, Granulicatella elegans, G. hemolysans, and Neisseria subflava. On the soft palate, S. mitis, other cultivable and not-yet-cultivable species of Streptococcus, G. adiacens and G. hemolysans were predominant. Following this study, Egija Zaura and colleagues examined the diversity and uniqueness of individual oral microbiomes using pyrosequencing for the first time [18]. In this study it was observed that the cheek samples were the least diverse while the dental samples showed the highest diversity. Principal component analysis discriminated the profiles of the samples originating from shedding mucosal surfaces from the samples that were obtained from the non-shedding surfaces [18].
Site-specialization of human oral Gemella species
Published in Journal of Oral Microbiology, 2023
Julian Torres-Morales, Jessica L. Mark Welch, Floyd E. Dewhirst, Gary G. Borisy
Members of the genus Gemella are core species of the human oral microbiome [1] found in healthy subjects and are therefore regarded as commensals, although they are known to cause opportunistic infections. Compared to other members of the human microbiota, the genus has not attracted much attention: a search in PubMed for ‘Gemella’ yielded 634 publications (as of March 24, 2023), mostly about its presence in or isolation from clinical samples of patients with endocarditis, oral diseases, wound infections, vaginosis, or other conditions. The basic microbiology literature indicates that members of this genus are non-motile cocci, facultatively anaerobic, capnophilic, of low G+C content, catalase-negative, oxidase-negative, with a tendency to grow in pairs, tetrads, or short chains [2–4]. Gemella species are capable of fermenting glucose into lactate and acetate as major metabolic end products [5]. However, the roles that species of Gemella play in the human microbiome as a whole remain to be established.
Oral microbiome in older adults with mild cognitive impairment
Published in Journal of Oral Microbiology, 2023
Dongxin Da, Qianhua Zhao, Hao Zhang, Wanqing Wu, Xiaoli Zeng, Xiaoniu Liang, Yiwei Jiang, Zhenxu Xiao, Jin Yu, Saineng Ding, Li Zheng, Ying Zhang, Xiaogang Xu, Ding Ding
Despite the overall similarity of alpha and beta diversity, we characterized some differently abundant taxa in both groups. In the results of LEfSe, Gemella haemolysans and Streptococcus gordonii were two species significantly enriched in cognitively normal individuals with the maximal AUC. Gemella haemolysans was a Gram-indeterminate bacteria found in the human oral, intestinal and respiratory tracts. Tomohiro Miyoshi et al. have found the protein components in the culture supernatant of Gemella haemolysans directly suppressed the growth of P. gingivalis [27]. P. gingivalis was the major pathogens of periodontitis. Several studies had proved the association between these periodontal pathogens and cognitive dysfunction [28–30]. In the brains of AD patients, Dominy et al. found P. gingivalis and its virulence factor, gingipains, whose levels were correlated with amyloid plaques [28]. Bacteria of the genus Streptococcus are acquired at birth and the first to colonize the oral cavity. Streptococcus gordonii could produce much alkali that neutralize the acid-producing action of Streptococcus mutans [31]. Streptococcus gordonii also possesses two paralogs of AgI/II, SspA and SspB, mediating its adhesion to human and bacterial receptors [32].