Microbioma oral: variabilidad entre regiones y poblaciones / Oral Microbiome: Variability Between Regions and Populations

Resumen De acuerdo con la Organización Mundial de la Salud (OMS), 3.58 billones de personas son afectadas por desórdenes orales, donde la caries, seguida de la enfermedad periodontal son las más frecuentes y las principales causas de daño al tejido pulpar y pérdida de órganos dentales. En México, el Sistema de Vigilancia Epidemiológica de Patologías Bucales (SIVEPAB) reportó que el 53% de la población se ve afectada por algún grado de enfermedad periodontal, mientras que en promedio la caries afecta al 93.3% de la población de entre 20 a 85 años y más, así como a alrededor del 50.0% de niños y adolescentes, por lo que ambos padecimientos son considerados un problema de salud pública importante en este país. Adicionalmente, se sabe que el microbioma oral humano está asociado con la salud y la enfermedad bucodental. Entre los géneros bacterianos que comúnmente habitan la cavidad oral humana destacan Streptococcus spp., Lactobacillus spp. y Porphyromonas spp. que, a través del desequilibrio del microbioma oral (disbiosis), se asocian con la caries o la enfermedad periodontal. En vista de que estamos constantemente expuestos a este tipo de infecciones crónicas inflamatorias, se sabe que las bacterias orales se trasladan a otras partes del cuerpo contribuyendo al desarrollo y exacerbación de la inflamación sistémica y otras enfermedades. Ya que existen factores como la ubicación geográfica, además de la disbiosis, la edad, la dieta y la genética, que influyen en la variabilidad del microbioma humano. Es importante analizar la diversidad del microbioma oral desde esta perspectiva, ya que el conocimiento que se tiene hasta el momento aún es escaso; por lo anterior se realizó una búsqueda de artículos publicados entre 2010 y 2020 en poblaciones de Asia, África, América y Europa, con el fin de responder la siguiente pregunta: ¿el factor geográfico tiene un impacto en la composición de la variabilidad del microbioma oral humano?

Abstract According to the World Health Organization (WHO), 3.58 billion people were affected by oral disorders, where caries, followed by periodontal disease are the most frequent and the main causes of damage to pulp tissue and loss of dental organs. In Mexico, the Epidemiological Surveillance System for Oral Pathologies (SIVEPAB) reported that 53% of the population is affected by some degree of periodontal disease, while on average caries affects 93.3% of the population between 20 and 85 years old and older, as well as about 50.0% of children and adolescents, so both conditions are considered an important public health problem in this country. Additionally, the human oral microbiome is known to be associated with oral health and disease. An imbalance in the oral microbiome (dysbiosis) can result in the proliferation of Streptococcus mutans and Porphyromonas gingivalis, linked to caries and periodontal disease. The latter two conditions, the most prevalent oral diseases worldwide, are the main causes of damage to pulp tissue and loss of dental organs. In the presence of these pathologies, constant exposure to the corresponding inflammatory chronic infection could lead to the translocation of oral bacteria to other parts of the body, where they may contribute to the development and/or exacerbation of systemic inflammation and trigger disease. Since age, diet, genetics, and geographical location are known to influence the variability of the human microbiome, it is important to analyze differences in the oral microbiome between distinct populations. Up to now, little attention has been given to this task. The current review carried out for articles published between 2010 and 2020 and describes the human oral microbiome in populations of Asia, Africa, America and Europa, to explore whether geographical differences have an impact on the variability of the human oral microbiome.

Análise do perfil microbiano de lesões orais potencialmente malignas / The microbial profile of potentially malignant oral disorders

As lesões orais potencialmente malignas são alterações que exibem maior risco de transformação maligna em comparação com a mucosa saudável. Apesar de sua relevância, a literatura ainda não definiu o papel da microbiota na etiologia e no processo de malignização dessas lesões. Assim, neste trabalho, realizamos um estudo do tipo caso controle de caráter longitudinal, prospectivo e quantitativo onde avaliamos as populações bacterianas do microbioma oral em pacientes com lesões orais potencialmente malignas. Para isso, utilizamos um questionário estruturado e coletamos swabs orais em pacientes portadores de leucoplasia, eritroplasia, líquen plano, lesão liquenóide oral e também controles saudáveis. Participaram do estudo 60 indivíduos, no período de coleta de 2018 à 2020,sendo 39 do grupo caso e 21 do grupo controle. A maioria dos pacientes era do sexo feminino (42/60; 70%) com média de idade de 57 anos, e mais da metade dos indivíduos eram não fumantes (35/60; 58,3%) e etilistas (36/60; 60%). Dentre os diagnósticos, observamos a maioria dos indivíduos com líquen plano oral/lesão liquenóide oral (13/39), seguidos de leucoplasia homogênea (10/39), eritroleucoplasia (8/39), leucoplasia verrucosa proliferativa (6/39) ou eritroplasia (2/39). A borda da língua foi o local mais comumente acometido, com a maioria apresentando múltiplos sítios (21/39). A displasia epitelial foi avaliada nas lesões, exceto líquen plano e lesões liquenóides, e 18 pacientes tiveram algum grau de displasia. Um total de 73 amostras tiveram a região V3-V4 do gene 16S rRNA amplificada e sequenciada, sendo 60 amostras referentes à primeira coleta e 13 ao segundo momento de coleta dos participantes do grupo caso, sendo que 3/13 desses indivíduos vieram a ter um diagnóstico de carcinoma espinocelular oral. Identificamos maior quantidade de genomas bacterianos por genomas humanos nas amostras do grupo caso, no entanto, a diversidade e composição bacteriana foram semelhantes entre casos e controles. No total, identificamos 9 filos, 15 classes, 24 ordens, 47 famílias e 67 gêneros bacterianos. O gênero mais abundante foi Streptococcus em ambos os grupos, com menor frequência nos casos. Encontramos ainda alta abundância dos gêneros Granulicatella e Blautia nos indivíduos com lesões orais e menor abundância de Methylobacterium, Lautropia e Oribacterium. Observamos também que a abundância de Granulicatella e Bergeyella foi maior nas lesões com displasia epitelial. A transformação maligna em carcinoma espinocelular oral ocorreu em 10/39 (25,6%) dos casos, onde a presença de displasia epitelial aparentou ser um fator de risco relevante. A diversidade bacteriana foi semelhante entre os indivíduos do grupo caso que sofreram ou não malignização, porém, a abundância dos gêneros Capnocytophaga, Finegoldia, Prevotella e Prevotella 2 foi maior nas amostras que sofreram malignização, mesmo antes do processo acontecer. Não encontramos diferenças na composição bacteriana entre os dois tempos de coleta, ao diagnóstico e após aproximadamente um ano, e também não observamos diferenças significativas na quantidade de DNA bacteriano e humano. Ao inferirmos as vias metabólicas derivadas das bactérias identificadas nas amostras, observamos também similaridade entre os grupos caso e controle, e apenas duas vias preditas apresentaram abundância com diferenças estatisticamente significativas entre ambos. Dessa maneira, nossos resultados sugerem que distúrbios orais potencialmente malignos podem estar associados a uma disbiose do microbioma oral, e que alguns gêneros bacterianos podem ser potenciais biomarcadores ou agentes importantes neste processo biológico.

Oral potentially malignant disorders have a higher risk of becoming cancer than healthy mucosal tissues. However, up until now, the literature did not define the role of the microbiota in the origin and development of malignancy in these lesions. Thus, here we conducted a longitudinal, prospective, and quantitative case-control study where we evaluated the bacterial composition of the oral microbiome in patients with potentially malignant lesions. Therefore, we used a structured questionnaire and performed oral swabs on patients with leukoplakia, erythroplakia, lichen planus, oral lichenoid lesion, and healthy controls. A total of 60 individuals, collected between 2018 to 2020, were enrolled in the study, of which 39 were cases and 21 were controls. The majority of patients were female (42/60; 70%) with a mean age of 57 years and over half of the individuals were non-smokers (35/60; 58.3%) and alcoholics (36/60; 60%). Among the diagnoses, there were oral lichen planus/oral lichenoid lesion (13/39), homogeneous leukoplakia (10/39), erythroleukoplakia (8/39), proliferative verrucous leukoplakia (6/39) and erythroplakia (2/39). The tongue edge was the most common location affected, with the majority having multiple sites (21/39). Epithelial dysplasia was assessed in the lesions, except for lichen planus and lichenoid lesions, and 18 patients had some degree of dysplasia. A total of 73 samples had the V3-V4 region of the 16S rRNA gene amplified and sequenced, in which 60 samples were collected at diagnosis (first collection point) and 13 samples were collected after approximately a year (second moment of collection). At least 03/13 of these patients were later diagnosed with oral squamous cell carcinoma. We identified a higher amount of bacterial per human genomes in the samples of the case group, however, the bacterial diversity and composition were similar between cases and controls. We identified 9 phyla, 15 classes, 24 orders, 47 families, and 67 bacterial genera. The most abundant genus was Streptococcus in both groups, with lower relative frequency in the individuals with potentially malignant lesions. We found a higher abundance of the genera Granulicatella and Blautia in the cases and lower abundance of Methylobacterium, Lautropia, and Oribacterium. We also observed that the abundance of Granulicatella and Bergeyella increased in the lesions with epithelial dysplasia. Malignant transformation into oral squamous cell carcinoma occurred in 10/39 (25.6%) of the cases patients, where the presence of epithelial dysplasia was a relevant risk factor. The bacterial diversity was similar between the individuals in the case group regardless if they malignized or not, however, the abundance of the genera Capnocytophaga, Finegoldia, Prevotella, and Prevotella 2 was higher in the samples that underwent malignization, even before this process took place. We did not find significant differences in the bacterial composition between the two collection points and we also did not observe significant differences in their amount of bacterial and human DNA. When inferring the metabolic pathways derived from the bacteria identified in the samples, we also observed similarity between the case and control groups, and only two predicted pathways showed abundance with statistically significant differences between them. Thus, our results suggest that potentially malignant oral disorders may be associated with a dysbiosis of the oral microbiome, and that some bacterial genera may be potential biomarkers or important agents in this biological process.

Enfermedad periodontal asociada al embarazo / Periodontal disease associated with pregnancy

La gingivitis es la enfermedad más prevalente, pues afecta entre un 5% y un 70% de la población mundial, y puede incluso llegar hasta un 90%. En cambio, la enfermedad periodontal (EP) alcanza un promedio del 30% al 80%, y es más frecuente a partir del segundo trimestre de embarazo. En América Latina, afecta entre un 30% y un 40% de la población. Se estima que durante el embarazo hay un mayor riesgo a contraer enfermedad periodontal en una proporción de 1 de cada 5 mujeres. La enfermedad periodontal es una enfermedad inflamatoria que perjudica a los tejidos de soporte del diente (encía, cemento radicular, ligamento periodontal y hueso alveolar).Se ha demostrado que existe una relación directa entre el agravamiento de la EP con el embarazo. Esto se debe a la variación hormonal que ocurre en este periodo, la cual promueve el crecimiento excesivo de microorganismos patógenos responsables de la inflamación gingival. Entre estos microorganismos patógenos encontramos a Prevotella intermedia y Porphyromonas gingivalis. Esta última, junto a Fusobacterium nucleatum, son capaces de atravesar la barrera placen-taria y causar infecciones y resultados adversos en el embarazo, tales como parto prematuro, preeclampsia y muerte fetal. (AU)

Gingivitis is the most prevalent disease worldwide, affecting from 5 to 70% of the population and reaching up to 90%. On the other hand, the mean prevalence of periodontal disease (PD) is 30 to 80%, being more frequent in the second trimester of pregnancy. Periodontal disease is an inflammatory disease of the tissues supporting (gingiva, root cement, periodontal ligament and alveolar bone). In Latin America, PD affects between 30 and 40% of the population, and it is estimated that 1 to 5 women will develop PD during pregnancy. It has been shown that there is a direct relationship between the aggravation of PD and pregnancy. This is due to hormonal changes during gestation, which promote the excessive growth of pathogenic microorganisms responsible for gingival inflammation.These pathogenic microorganisms include Prevotella intermedia and Porphyromonas gingivalis. The latter, together with Fusobacterium nucleatum. are able to cross the placental barrier causing infections and adverse preg-nancy outcomes, such as premature birth, preeclampsia, fetal death and metrial arteritis. (AU)

Microbioma humano y microbioma oral. Una revisión / Human and oral microbiome. A review

EL microbioma humano es definido como el genoma colectivo de una población compuesta por bacterias, hongos, virus y protozoos que residen en los diferentes nichos ecológicos del cuerpo humano. El microbioma contribuye a mantener las funciones metabólica, proteger el cuerpo contra los patógenos, es esencial para el desarrollo de la inmunidad y de la nutrición. Muchas enfermedades pueden ser explicadas debido a la alteración en el equilibrio del microbioma. (AU)

The human microbiome is defined as the colective genomes of the microbes composed of bacteria, fungi, viruses and protozoa that residen in the human body. These microbes have the potential to impact the physiology, both in health and desease. Microbiome contribute methabolic functions, protect tha body against pathogens, is essential for development of inmunity and nutrition. Many deseases may possibly be explained by alterations in the microbiome. (AU)

Avances en el Estudio de la Diversidad Bacteriana Oral Asociada a Caries Dental Mediante el Estudio Genómico / Advances in the Study of Oral Bacterial Diversity Associated with Dental Caries by Genomic Study

La caries es una enfermedad infecciosa, transmisible y multifactorial, que conduce a la pérdida de minerales reversible o irreversible de los tejidos duros susceptibles del diente, por acción de productos ácidos provenientes de la fermentación de los hidratos de carbono de la dieta por la actividad metabólica del biofilm adherido a la superficie dentaria. Aunque tradicionalmente se ha considerado al Streptococcus mutans como el responsable de la enfermedad, actualmente otras bacterias, denominadas no mutans, se han asociado con el inicio, progresión y actividad de la enfermedad en esmalte, dentina y cemento radicular. Para profundizar el estudio de la diversidad bacteriana oral asociada a caries dental se han aplicado diversas metodologías, dentro de las cuales destaca el estudio del metagenoma oral. Este nos permite estudiar comunidades bacterianas completas mediante el análisis del DNA, en un determinado ambiente sin necesidad de aislar y cultivar las especies, entregando información sobre la diversidad taxonómica y filogenética de estas comunidades. Existen diferentes métodos de análisis de la diversidad bactariana, entre los que tenemos el análisis del ARNr 16S mediante electroforésis, PCR, microarreglos, secuenciamiento de última generación, entre otros. El estudio del metagenoma oral ha permitido identificar especies que no han podido ser aisladas por métodos convencionales, además de identificar su presencia o ausencia en las distintas etapas del desarrollo de la enfermedad de caries dental, permitiendo un mejor conocimiento del desarrollo de esta patología. El estudio basado en el metagenoma ha dado a conocer una diversidad microbiana oral inesperada, dando información relevante para la actualización de los conocimientos y así identificar nuevos objetivos terapéuticos. El propósito de esta revisión bibliográfica es exponer los principales resultados que ha aportado el estudio del metagenoma sobre la diversidad microbiana, aplicado específicamente a la comunidad bacteriana oral.

Dental caries is an infectious, transmissible and multifactorial disease, which leads towards a reversible and irreversible loss of minerals found in hard tissues of a tooth, caused by acids from carbohydrates fermentation due to metabolic activity of the biofilm attached to the tooth surface. Although Streptococcus mutans has been thought to be responsible for tooth decay, another bacterium named no mutans has been linked to the beginning, progression and activity of the disease in the enamel, dentine and cement. One of the methodologies put into practice to deepen the study of oral bacteria diversity related to carious cavities is oral metagenome. This methodology allows the study of whole bacterial groups by the analysis of DNA in a particular environment without the need of isolating and cultivating species, providing information about the taxonomical and phylogenetic diversity of these groups. There are different methods to study the bacterial diversity, including 16 S rRNA analysis through electrophoresis, PCR, microarrays, next generation sequence (NGS). The metagenome tool permits to recognize species that have not been able to be isolated by conventional methods. As well as identify its presence or absence in the different stages of the dental caries development, which allows a better understanding of development of the disease. The metagenome-based study has revealed an unexpected oral microbial diversity, giving information relevant to the updating of knowledge and identifies new therapeutic targets. The purpose of this review is to present the main results has brought the study of the metagenome on microbial diversity, applied specifically to the oral bacterial community in health and caries disease.