Microbiological study of periodontal disease in populations with HIV: a systematic review and meta-analysis

Background: No systematic review/meta-analysis has been conducted on the microbiological prole associated with the occurrence of periodontitis in patients with HIV. The aim of this study was to evaluate the prevalence of identied bacteria in HIV-infected patients with periodontal disease. Methods: Three English electronic databases (MEDLINE (via PubMed), SCOPUS, and Web of Science) were searched systematically from the beginning to 13 February 2021. The frequency of each identied bacteria in HIV-infected patients with periodontal disease was extracted. All meta-analysis methods were performed using STATA software. Results: Twenty-two articles met inclusion criteria and enrolled into the systematic review. This review analyzed a total of 965 HIV-infected patients with periodontitis. The prevalence of periodontitis was higher in HIV-infected male patients (83% (CI95%: 76-88%)) compared to females (28% (CI95%: 17-39%)). In our study, the pooled prevalence of necrotizing ulcerative periodontitis and necrotizing ulcerative gingivitis in patients with HIV infection was 67% (CI95%: 52-82%) and 60% (CI95%: 45-74%), while a lower prevalence of linear gingivitis erythema was reported (11% (CI95%: 5-18%)). More than 140 bacterial species were identied from HIV-infected patients with periodontal disease. High prevalence of Tannerella forsythia (51% (CI95%: 5-96%)), Fusobacterium nucleatum (50% (CI95%: 21-78%)), Prevotella intermedia (50% (CI95%: 32-68%)), Peptostreptococcus micros (44% (CI95%: 25-65%)), Campylobacter rectus (35% (CI95%: 25-45%)), and Fusobacterium spp. (35% (CI95%: 3-78%)) in HIV-infected patients with periodontal disease was found. Conclusion: Our study demonstrated that the prevalence of red and orange complex of bacteria in HIV patients with


Background
Globally, the number of individuals infected with the human immunode ciency virus (HIV) continues to rise. At the end of 2019, nearly 38.0 million people worldwide were diagnosed with HIV, with 1.7 million being newly infected (http://www.who.int/news-room/fact-sheets/detail/hiv-aids) [1].
HIV periodontal manifestations were rst identi ed in 1987 [2]. At least 24 distinct oral lesions have been identi ed in the HIV literature, but only ten of these are observed consistently. In decreasing order of prevalence, they are oral candidiasis, oral hairy leucoplakia, herpes simplex virus infection, Kaposi's sarcoma, nonspeci c ulceration, aphthous ulcers, periodontal disease, and salivary gland disease, oral melanotic hyperpigmentation, and oral warts [3].
Periodontal disease is closely linked to HIV infection and refers to a group of in ammatory-based diseases that include gingivitis and periodontitis [4]; however, it is unclear if the combination of HIV infection and periodontitis raises the risk of aggravation of their periodontitis [5,6].
Numbers of scienti c research has been dedicated to the study of periodontal-disease-associated micro ora, ranging from traditional cultural techniques to new genetic, whole-genome, and proteomic approaches [8].
Bacteria that cause periodontal disease can be categorized based on how they interact with each other when colonizing the gingival sulcus [9]. There is a balance between microbial challenge and host immune response; any change to that with the presence of other modifying factors is responsible for periodontal infection clinical manifestation. [10].
For several years, scientists have recognized that studying oral health and disease requires recognizing and comprehending the pathogenic potential of all bacteria that colonize the oral cavity [11]. More than 700 bacterial species have been identi ed in the subgingival plaque, and some of these microorganisms have been linked to the initiation /progression of periodontal diseases. Porphyromonas gingivalis, Tannerella forsythia (previously known as Bacteroides forsythia), and Actinobacillus actinomycetemcomitans were classi ed as key pathogens. In 1998, Socransky et al. proposed that understanding oral diseases could be enhanced by concentrating on consortia of species rather than individual pathogens. They discovered ve groups of bacteria, or complexes, that were present together in periodontitis on several occasions. They hypothesized that the most pathogenic complex included P. gingivalis, T. forsythia, and Treponema denticola (the red complex) and was dependent on earlier colonization of the pocket by the orange complex, a group of less pathogenic species [11,12].
There are several unanswered questions in dental science [13], especially in the microbiology, immunology, in ammatory host response, and epidemiological developments of periodontal disease in HIV-infected populations. No systematic review/meta-analysis has been conducted on the microbiological pro le associated with the occurrence of periodontitis in patients with HIV. The aim of this study was to evaluate the prevalence of identi ed bacteria in HIV-infected patients with periodontal disease.

Methods
Search method and selection criteria Three English electronic databases (MEDLINE (via PubMed), SCOPUS, and Web of Science) were searched systematically from the beginning to 13 February 2021. Publication searches were performed by various combinations of the following terms: "Immunode ciency" or "Human immunode ciency virus" AND "Periodontitis" AND "Bacteria" or "Oral microbiota" or "Oral microbial" or "Aggregatibacter actinomycetemcomitans" or "Porphyromonas gingivalis" or "Tannerella forsythia" or "Prevotella intermedia" or "Treponema denticola" or "Fusobacterium nucleatum" or "Campylobacter rectus" or "Eikenella corrodens" or "Eikenella corrodens" or "Peptostreptococcus micros". The reference lists of selected articles were also screened manually and applicable articles were included. Abstracts of papers presented at conferences were not reviewed because they lacked su cient details data. Dissertations and thesis were not included. The study was conducted according to the guidelines of PRISMA (the preferred reporting items for systematic reviews and meta-analyses.

Inclusion criteria
Titles and abstracts of all articles were screened by one reviewer, and eligibility of the screened articles was assessed by two independent investigators using the following criteria: titles, abstracts, and full texts. When necessary, authors were contacted for additional information. Studies were excluded if they had insu cient data.

Periodontal diseases
A periodontal diseases related to HIV was categorized as necrotizing ulcerative periodontitis, necrotizing ulcerative gingivitis, and linear gingivitis erythema [14].

Bacterial complex de nition
Six closely related classes of bacterial species were included for meta-analysis. Colors ranging from red to yellow have distinct connotations. The most pathogenic color is red, while yellow represents commensales. A red complex composed of P. gingivalis, T. denticola, and T. forsythia that is highly correlated with the clinical progression of chronic periodontitis [15], an orange complex included anaerobic gram-negative species such as Prevotella intermedia, Prevotella nigrescens, Prevotella micros, and Fusobacterium nucleatum, a yellow complex consisting of members of the genus Streptococcus, a green complex included Capnocytophaga species, A. actinomycetemcomitans serotype A, Eikenella corrodens and Campylobacter and a purple complex containing of Veillonella parvula and Actinomyces odontolyticus [16].

Exclusion criteria
Investigations with not-relevant topics, review and case report articles, books, non-english articles or the ones worked on non-human subjects were excluded.
The articles, in which bacterial information was given in a graph/phylogenetic tree or as mean value or relative distribution, were deleted. The articles, in which bacterial frequency data was reported among the sites or isolates studied, were also omitted.

Data extraction
Data from eligible studies was extracted independently by 2 reviewers and checked by a third reviewer. Disagreements among the reviewers were resolved through discussion. The following data were extracted from included studies; rst author and publication year, country region, sample size, sex and age of patients, number of HIV-positive patients diagnosed with periodontal diseases, type of sampling, type of the periodontal diseases, diagnostic methods used, and the frequency of each type of microorganisms. If the data was reported as a percentage, the number was calculated through the use of proportions. The frequency of each identi ed bacteria in HIV-infected patients with periodontal disease was extracted.

Data analysis
All meta-analysis methods were performed using STATA (Release 12. statistical software. College Station, Texas: STATA Corp LP). Results of the metaanalysis were illustrated by a forest plot diagram, which demonstrated the pooled prevalence of each microorganism and their relevant 95% con dence interval (CI).
The Cochrane Q-test and the inverse variance index (I 2 ) were used to evaluate the heterogeneity in this study. The I 2 values of 25%, 50%, and 75% were representatives of low, moderate and high heterogeneity, respectively [17].
Publication bias was estimated by a funnel plot diagram based on Egger's regression test [18].

Quality assessment
The quality of the studies included in this study was independently evaluated by two reviewers using the Joanna Briggs Institute's updated Critical Appraisal Checklist for Prevalence Studies, which includes nine questions that the reviewers answered for each of the qualifying studies. Any dispute was resolved through discussion [19].

Results
Of the 2075 records identi ed in the mentioned electronic databases, 559 and 252 articles remained after duplicates removal and title-based screening. By screening of full-texts, 230 records were excluded for various reasons including reported bacterial data in graph/phylogenetic tree or as mean value or relative distribution. Twenty-two articles met inclusion criteria and enrolled into the systematic review (Fig. 1).
This review analyzed a total of 965 HIV-infected patients with periodontitis. Demographic and clinical information is presented in Table 1. Sample sizes of the HIV-infected group with periodontitis ranged from 7 to 82. With regard to the applied method for organism identi cation, the majority of the studies used the culture method [20][21][22][23][24][25][26][27][28][29][30][31], while ve studies used the polymerase chain reaction (PCR) method [26,[32][33][34][35]. No study considered children exclusively. The age groups of the investigated patients were > 15 years in 13 papers, respectively. However, the age group of the study population was not mentioned in the remaining 9 studies. Regarding sampling, in the majority of the studies (n = 11), subgingival plaque was used as the specimen for analysis. However, the periodontal pocket (n = 3), saliva (n = 3), gingival papilla and contiguous supragingival plaque (n = 1), gingival pockets (n = 1), bio lm samples (n = 1), and plaque (n = 2), and feces (n = 1) were also applied in other studies.
To calculate the pooled prevalence of associated groups of bacterial species of each complex (if the number of studies were more than 3), the cumulative meta-analysis was performed and the forest plots indicated separately.
Based on the results of Egger's regression test, the publication bias among included studies could not be ignored (p-value < 0.0001).

Discussion
To our knowledge, this is the rst systematic review and meta-analysis to determine the periodontal conditions and the distribution of associated groups of bacterial species in HIV-infected patients with periodontal disease.
We found a high prevalence of red complex bacteria, particularly T. forsythia in HIV-infected patients with periodontal disease, which is basically in agreement with some previous studies [41,42].
Periodontal infections have been linked to an increased risk of HIV-1 reactivation in infected people, as well as the progression of acquired immunode ciency syndrome (AIDS). Furthermore, it would suggest that preventing and treating periodontitis induced by red complex infection could effectively inhibit further clinical progression of AIDS [43].
The periodontal clinical parameters are closely linked to the occurrence of the red complex [44]. T. forsythia, P. gingivalis, and A. actinomycetemcomitans are strongly related to the onset of periodontal infection, disease development, and failed periodontal therapy [42,45]. However, in this study, the pooled prevalence of T. forsythia was higher than P. gingivalis (23% (CI95%: 11-39%)) and A. actinomycetemcomitans (15% (CI95%: 8-24%)), respectively. Despite the fact that P. gingivalis is one of the most common microbial diseases in humans [43], it was found to have a lower prevalence in HIV-infected patients with periodontal disease (23% (CI95%: 11-39%)). Moreover, P. gingivalis can be present even though there is no disease, ruling out its position as an exogenous pathogen [46].
F. nucleatum has been shown to be a major marker for destructive periodontal disease in adult subjects. It is also likely to play a role in bio lm colonization and lead to the reducing conditions required for the emergence of oxygen-intolerant anaerobes [46]. It has also been mentioned that F. nucleatum promotes P. gingivalis invasion of host cells [47].
Bacterial organisms should be able to colonize the subgingival region and develop virulence factors that either directly (enzymes and toxins) or indirectly (antigens and activators) cause an individual's destructive in ammatory response and periodontal tissue injury. Proteases, alkali and acid phosphatases produced by microorganisms, fatty and organic acids, IgG-and IgA-proteases, chondroitinsulfatase, and toxic products including endotoxins, leukotoxin, mucopeptides of the bacterial wall, and end-products of metabolism are types of agents that directly damage periodontal tissues [42].
On the other hand, certain variations in cellular immunity can also promote the proliferation of virulent commensals or combinations of bacterial species, and possible symbiotic relationship between the species [48]. The role of all recognized periodontal bacteria in various periodontal diseases is unknown, but it is known that these bacteria can function in a variety of ways, including passively occupying niches, restricting a periodontal pathogen's ability to bind to suitable tissue surfaces, improving a pathogen's vitality and growth, and enhancing a pathogen's ability to produce virulence factors [42].
Increased oral health knowledge and the discovery of different disease-causing pathogens contribute in the reduction of risk factors for oral diseases. Certain treatments have demonstrated promising results, and could be investigated further in prospective clinical trials [16].
Poor oral hygiene is a typical clinical nding in HIV patients. Despite the obvious need for oral health services, these patients are not provided with proper dental care due to the HIV-related stigma that exists in many settings, putting them at a greater risk for developing oral and systemic diseases [49,50].
Therefore, designing and implementing of low-cost and easily available diagnostic and therapeutic methods for periodontal diseases is highly recommended [51].
This study has several limitations. The stage of HIV infection and its progression was not mentioned in the studies and this can affect the nal evaluation. There are evident gaps in knowledge in relation to periodontal diseases in patients with HIV in some countries in Africa, Asia and Europe. Data heterogeneity within these studies can be explained by differences in detection strategies, genetic history, behavioral and/or environmental factors.

Conclusion
In conclusion, our study demonstrated that the prevalence of red and orange complex of bacteria in HIV patients with periodontal disease is relatively high.
This information will eventually lead to the implementation of innovative and/or more effective preventive and therapeutic methods, as well as diagnostic applications in periodontics. Early diagnosis, e cient periodontal management, proper oral hygiene maintenance is the key for the treatment of periodontal manifestation of HIV.

Consent for publication
Not applicable.

Availability of data and materials
All data obtained

Competing interests
The authors declare that they have no competing interests.     Forest plot analysis of the prevalence of bacterial species of blue complex group in HIV-infected cases with periodontal disease (A= Actinomyces israelii, B= Actinomyces naeslundii, C= Actinomyces viscosus)

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