Microorganisms: crucial players of smokeless tobacco for several health attributes

16S rDNA-Based Amplicon Analysis Unveiled a Correlation Between the Bacterial Diversity and Antibiotic Resistance Genes of Bacteriome of Commercial Smokeless Tobacco Products

The distribution of bacterial-derived antibiotic resistance genes (ARGs) in smokeless tobacco products is less explored and encourages understanding of the ARG profile of Indian smokeless tobacco products. Therefore, in the present investigation, ten commercial smokeless tobacco products were assessed for their bacterial diversity to understand the correlation between the inhabitant bacteria and predicted ARGs using a 16S rDNA-based metagenome analysis. Overall analysis showed the dominance of two phyla, i.e., Firmicutes (43.07%) and Proteobacteria (8.13%) among the samples, where Bacillus (9.76%), Terribacillus (8.06%), Lysinibacillus (5.8%), Alkalibacterium (5.6%), Oceanobacillus (3.52%), and Dickeya (3.1%) like genera were prevalent among these phyla. The phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt)-based analysis revealed 217 ARGs which were categorized into nine groups. Cationic antimicrobial polypeptides (CAMP, 33.8%), vancomycin (23.4%), penicillin-binding protein (13.8%), multidrug resistance MDR (10%), and β-lactam (9.3%) were among the top five contributors to ARGs. Staphylococcus, Dickeya, Bacillus, Aerococcus, and Alkalibacterium showed their strong and significant correlation (p value < 0.05) with various antibiotic resistance mechanisms. ARGs of different classes (blaTEM, blaSHV, blaCTX, tetX, vanA, aac3-II, mcr-1, intI-1, and intI2) were also successfully amplified in the metagenomes of SMT samples using their specific primers. The prevalence of ARGs in inhabitant bacteria of smokeless tobacco products suggests making steady policies to regulate the hygiene of commercial smokeless tobacco products.

Oral microbiome and its relationship with oral cancer

ABSTRACT

As the initial point for digestion, the balance of oral microorganisms plays an important role in maintaining local and systemic health. Oral dysbiosis, or an imbalance in the oral microbial community, may lead to the onset of various diseases. The presence or abnormal increase of microbes in the oral cavity has attracted significant attention due to its complicated relationship with oral cancer. Oral cancer can remodel microbial profiles by creating a more beneficial microenvironment for its progression. On the other hand, altered microbial profiles can promote tumorigenesis by evoking a complex inflammatory response and affecting host immunity. This review analyzes the oncogenic potential of oral microbiome alterations as a driver and biomarker. Additionally, a potentially therapeutic strategy via the reversal of the oral microbiome dysbiosis in oral cancers has been discussed.

Smokeless Tobacco Harbors Bacteria Involved in Biofilm Formation as Well as Salt and Heavy Metal Tolerance Activity

In our previous culture-independent study on smokeless tobacco products, we have observed a strong positive correlation between several bacteria and genes involved in nitrate/nitrite reduction, biofilm formation, and pro-inflammation. Therefore, the present investigation was carried out to analyze the inhabitant bacterial population of the Indian ST products for assessing the health-associated risk attributes using culture-dependent approach. Traditional cultivation approaches recovered several bacterial isolates from commercial ST products on different culture media. A high colony formation unit (CFU) count was observed that ranged from 173 × 104 to 630.4 × 105 per gram of ST products. Of the 74 randomly selected and distinct bacterial isolates, 17 isolates showed a significantly enhanced growth (p-value < 0.05) in the presence of the aqueous tobacco extract. On biochemical characterization, these bacteria were identified as the member of Bacillus, Enterobacter, Micrococcus, Providencia, Serratia, Pantoea, Proteus, and Pseudomonas. Most of these bacteria also exhibited biofilm-forming activity, where eight bacterial isolates were identified for strong biofilm-forming action. 16S rRNA-based molecular characterization of these bacteria identified them as Bacillus subtilis, Bacillus paralicheniformis, Enterobacter sp., Serratia marcescens, Pantoea anthophila, and Enterobacter cloacae. Moreover, these bacteria also exhibited the potential to withstand high salt and heavy metal concentrations. The findings demonstrate that Indian ST products are heavily populated with wide bacterial species exhibiting potential in biofilm formation, heavy metal resistance, and salt tolerance.

Smokeless Tobacco Cessation Support in Dental Hospitals in Pakistan: Dentists and Dental Patients' Perspectives on Current Practices, Support Needed, and Opportunities Available

INTRODUCTION

Despite evidence on the effectiveness of tobacco cessation interventions in dental settings, the implementation remains low, especially for smokeless tobacco (ST). The purpose of this study was to develop an understanding of the influences governing the implementation of ST cessation support in dental hospitals.

AIMS AND METHODS

A multicenter qualitative study was conducted at two tertiary-care dental hospitals, in Pakistan. Semi-structured interview guide, guided by the Capability-Opportunity-Motivation-Behavior (COM-B) model, were used to capture the views of dentists (n = 12) and dental patients (n = 12), regarding ST cessation support in dental hospitals. Framework approach was used to thematically analyze the data.

RESULTS

Screening of ST users in routine dental practice was seldom practiced and the cessation support offered was brief advice. Barriers identified by dentists included: Fear of offending and stereotyping patients; lack of knowledge and skills; lack of privacy; lack of belief in the effectiveness of behavioral support; lack of time and workload pressure; ST use amongst dentists; lack of referral systems and; the absence of a mandatory requirement of offering ST cessation support. Facilitators included: Delivering support through junior dentists and the length of interaction between the dentist and the patient. Naswar was the most common ST product used by dental patients. Patients reported receiving negligible cessation support from any healthcare provider.

CONCLUSIONS

A range of influences governing the implementation of ST cessation support in dental hospitals were identified. These findings can inform the implementation of behavioral interventions for ST cessation in dental and other clinical settings, in low and middle-income countries.

IMPLICATIONS

Smokeless tobacco control considerably lags, in comparison to the control of combustible tobacco. This is the first study that qualitatively explores the implementation of ST cessation support in dental settings in Pakistan. Utilizing the "Capability-Opportunity-Motivation-Behavior" model, it provides an in-depth understanding of the inability of dentists in implementing effective behavioral interventions for ST cessation support in routine dental practice. Highlighting the striking discrepancy between the patient's need for and receptivity towards cessation support and the dentists' concerns over their patients' receptivity towards cessation support, it calls for the need for effective implementation strategies to optimize dentist-led tobacco cessation interventions in low-resource settings.

Effects of fermentation chamber temperature on microbes and quality of cigar wrapper tobacco leaves

The natural fermentation of cigar tobacco leaves usually utilizes natural temperature and humidity for fermentation. Cigars produced in China are often fermented in winter, and the low environmental temperatures can lead to slow heating of the tobacco stack, affecting the cigar tobacco leaves quality. This study aimed to determine the minimum chamber temperature required to initiate the process of fermentation for cigar tobacco leaves and to explore the impact of temperature on the microbial community of tobacco leaves. Here, the cigar variety "Dexue 1" were subjected to stacking fermentation under three temperature parameters (20 ℃, 27 ℃, 34 ℃). With an increase in environmental temperature, the temperature inside the stack of cigar leaves increased significantly, the protein, total sugar, starch, and total alkaloid content in fermented tobacco leaves decreased, and the aroma components and amino acid content increased. Microbial richness and community diversity associated with fermented tobacco were highest at chamber temperatures of above 27 ℃. The relative abundance of Chryseobacterium and Rhodococcus was significantly negatively correlated with protein, alkaloids, total sugar, and starch, and positively correlated with amino acids and aroma components. Chryseobacterium and Rhodococcus may be responsible for the degradation of macromolecular substances and the conversion of favorable aromatic substances, thus improving the tobacco leaves quality. This study demonstrated that increasing the fermentation chamber temperature above 27 ℃ was conductive to raising the inner-stack temperature, increased microbial diversity and aromatic quality, reduced the strength and irritation, and extremely enhanced the overall quality of fermented cigar tobacco leaves. KEY POINTS: • The environmental temperature of the fermentation chamber has a significant impact on the quality of tobacco • Temperature > 27 ℃ can initiate the process of cigar tobacco leaves fermentation and increase inner-stack temperature and microbial diversity and abundance • Chryseobacterium and Rhodococcus may be related to the degradation of macromolecular substances and the transformation of aromatic substances, thereby improving the quality of tobacco leaves.

Alteration of oral bacteriome of smokeless tobacco users and their association with oral cancer

Smokeless tobacco (SLT) is certainly one of the major risk factors associated with oral cancer. Disruption of oral microbiota-host homeostasis contributes to the progression of oral cancer. Here, we profiled SLT users' oral bacterial composition and inferred their functions by sequencing 16S rDNA V₃-V₄ region and PICRUSt2, respectively. Oral bacteriome of SLT users (with or without oral premalignant lesions), SLT with alcohol co-users, and non-SLT consumers were compared. Oral bacteriome is shaped primarily by SLT use and the incidence of oral premalignant lesions (OPL). A significantly increased bacterial α-diversity was monitored in SLT users with OPL compared to in SLT users without OPL and non-users, whereas β-diversity was significantly explained by OPL status. Overrepresented genera were Prevotella, Fusobacterium, Veillonella, Haemophilus, Capnocytophaga, and Leptotrichia in SLT users having OPL. LEfSe analysis identified 16 genera as a biomarker that were differentially abundant in SLT users having OPL. The functional prediction of genes significantly increased for several metabolic pathways, more importantly, were nitrogen metabolism, nucleotide metabolism, energy metabolism, and biosynthesis/biodegradation of secondary metabolites in SLT users having OPL. Furthermore, HPV-16 and EBV, but not HPV-18, were considerably connected with the SLT users having OPL. Overall, this study provides evidence that SLT utilization and OPL development are associated with oral bacteriome dysbiosis indicating the enrichment of bacterial species known for their contribution to oral carcinogenesis. Therefore, delineating the cancer-inducing bacterial population in SLT users will facilitate the future development of microbiome-targeted therapies. KEY POINTS: • SLT consumption significantly elevates oral bacterial diversity. • Prevalent significant genera are Prevotella, Veillonella, and Haemophilus in SLT users with OPL. • SLT promotes the occurrence of the cancer-inducing bacterial population.

Altered oral microbiome in Sudanese Toombak smokeless tobacco users carries a newly emerging risk of squamous cell carcinoma development and progression

There are an estimated 6-10 million smokeless tobacco (Toombak) users in Sudan, the majority being males. Toombak is known to be a carcinogenic product that is likely to modify the oral microbiome spatiality into a high-risk potential for the development and progression of oral cancer, but previous studies are lacking in this field. Here, we endeavour for the first time the exploration of the oral microbiome in key mucosal areas of the oral cavity and assess the microbiome variations in premalignant and oral squamous cell carcinoma (OSCC) samples from both users and non-users of Toombak. 16S rRNA sequencing was performed on DNA obtained from pooled saliva, oral mucosa and supragingival plaque from 78 Sudanese users and non-users of Toombak, aged between 20 and 70 years. In 32 of the pooled saliva samples, the mycobiome (fungal) environment was analysed through ITS sequencing. Then, 46 formalin-fixed paraffin-embedded samples of premalignant and OSCC samples were collected, and their associated microbiomes sequenced. The oral Sudanese microbiome was found to be enriched in Streptococcaceae, but Staphylococcaceae were significantly more abundant amongst Toombak users. Genera enriched in the oral cavity of Toombak users included Corynebacterium_1 and Cardiobacterium while in non-users, Prevotella, Lactobacillus and Bifidobacterium were prominent. Aspergillus was the most abundant fungus in the mouths of Toombak users with a marked loss of Candida. The genus Corynebacterium_1 was abundant in the buccal, floor of the mouth and saliva microbiomes as well as in oral cancer samples from Toombak users indicating a possible role for this genus in the early stages of oral cancer development. An oral cancer microbiome that favours poor survival and metastasis in those who use Toombak also emerged that includes the genera Stenotrophomonas and Schlegelella. Those utilising Toombak carry an altered oral microbiome that may be an additional risk factor for this products carcinogenicity to the oral structures. These significant microbiome modulations are a newly emerging key driving factor in oral cancer development and progression in Toombak users while it is also shown that Toombak users carry an oral cancer microbiome that may increase the potential for a poorer prognosis.

Emerging Oral Nicotine Products and Periodontal Diseases

Oral nicotine pouches are emerging as a new "modern oral" nicotine product. These prefilled pouches contain nicotine, flavorings, and filling agents that dissolve in the mouth. Nicotine can be derived from tobacco leaf or chemical synthesis. Traces of TSNAs and toxic chromium were detected in the pouch products. This raises the concern about general and periodontal health. This review aims to update the current oral nicotine products research relating to periodontal disease and its relevance in periodontal inflammation. Nicotine interacts with host cells and affects inflammatory responses to microbial challenges. It may directly or indirectly deteriorate periodontal tissues by activating nicotinic acetylcholine receptors, repressing PDL fibroblasts cells, increasing cellular ROS and cytokines/chemokines, growth factors, breaking microbiota balance, and dysregulating miRNAs expression. Studies show that appealing flavorings contained in nicotine pouches pose harm to periodontal innate immune responses and increase penetration of nitrosamines. In addition, flavored ONPs increase the risk of dual or poly-tobacco products among young adults, stacking up detrimental effects on the periodontium. Given the recent growth of users, further studies are needed to elucidate the impact of ONPs, even poly-tobacco use, on systemic and periodontal health. Moreover, policymakers should ensure to avoid generating a new wave of nicotine addiction among youths in the U.S.

Taxonomic and functional profiling of Indian smokeless tobacco bacteriome uncovers several bacterial-derived risks to human health

Smokeless tobacco (ST) consumption keeps human oral health at high risk which is one of the major reasons for oral tumorigenesis. The chemical constituents of the ST products have been well discussed; however, the inhabitant microbial diversity of the ST products is less explored especially from south Asian regions. Therefore, the present investigation discusses the bacteriome-based analysis of indigenous tobacco products. The study relies on 16S amplicon-based bacteriome analysis of Indian smokeless tobacco (ST) products using a metagenomic approach. A total of 59,15,143 high-quality reads were assigned to 34 phyla, 82 classes, 176 orders, 256 families, 356 genera, and 154 species using the SILVA database. Of the phyla (> 1%), Firmicutes dominate among the Indian smokeless tobacco followed by Proteobacteria, Bacteroidetes, and Actinobacteria (> 1%). Whereas, at the genera level (> 1%), Lysinibacillus, Dickeya, Terribacillus, and Bacillus dominate. The comparative analysis between the loose tobacco (LT) and commercial tobacco (CT) groups showed no significant difference at the phyla level, however, only three genera (Bacillus, Aerococcus, and Halomonas) were identified as significantly different between the groups. It indicates that CT and LT tobacco share similar bacterial diversity and poses equal health risks to human oral health. The phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt 2.0) based analysis uncovered several genes involved in nitrate/nitrite reduction, biofilm formation, and pro-inflammation that find roles in oral pathogenesis including oral cancer. The strong correlation analysis of these genes with several pathogenic bacteria suggests that tobacco products pose a high bacterial-derived risk to human health. The study paves the way to understand the bacterial diversity of Indian smokeless tobacco products and their putative functions with respect to human oral health. The study grabs attention to the bacterial diversity of the smokeless tobacco products from a country where tobacco consumers are rampantly prevalent however oral health is of least concern.

Smokeless tobacco consumption induces dysbiosis of oral mycobiome: a pilot study

Smokeless tobacco (SLT) alters the oral microbiome of smokeless tobacco users. Dysbiosis of oral bacteriome has been determined; however, the mycobiome of SLT users has not been characterized. The oral mycobiome was assayed by amplification and sequencing of the fungal internal transcribed spacer (ITS1) region from oral swab samples of non-SLT users, SLT users (with or without oral lesions), and SLT with alcohol users. We observed that the richness and diversity of oral mycobiome were significantly decreased in SLT with oral lesions users than in non-users. The β-diversity analysis showed significant dissimilarity of oral mycobiome between non-users and SLT with oral lesions users. Linear discriminant analysis effect size and random forest analysis of oral mycobiome affirm that the genus Pichia was typical for SLT with oral lesions users. Prevalence of the fungal genus Pichia correlates positively with Starmerella, Mortierella, Fusarium, Calonectria, and Madurella, but is negatively correlated with Pyrenochaeta, Botryosporium, and Alternaria. Further, the determination of oral mycobiome functionality showed a high abundance of pathotroph-saprotroph-symbiotroph and animal pathogen-endophyte-epiphyte-undefined saprotroph at trophic and guild levels, respectively, indicating possibly major changes in normal growth repression of types of fungi. The oral mycobiome in SLT users was identified and comprehensively analyzed for the first time. SLT intake is associated with oral mycobiome dysbiosis and such alterations of the oral mycobiome may contribute to oral carcinogenesis in SLT users. This study will provide a basis for further large-scale investigations on the potential role of the mycobiome in SLT-induced oral cancer. KEY POINTS: • SLT induces dysbiosis of the oral microbiome that can contribute to oral cancer. • Oral mycobiome diversity is noticeably reduced in SLT users having oral lesions. • Occurrence of Pichia can be used as a biomarker for SLT users having oral lesions.

Delineating the Bacteriome of Packaged and Loose Smokeless Tobacco Products Available in North India

Smokeless tobacco product (STP) consumption is a significant public health threat across the globe. STPs are not only a storehouse of carcinogens and toxicants but also harbor microbes that aid in the conversion of tobacco alkaloids to carcinogenic tobacco-specific nitrosamines (TSNAs), thereby posing a further threat to the health of its consumers. The present study analyzed the bacterial diversity of popular dry and loose STPs by 16S rRNA gene sequencing. This NGS-based investigation revealed four dominant phyla Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria and identified 549 genera, Prevotella, Bacteroides, and Lactobacillus constituting the core bacteriome of these STPs. The most significantly diverse bacteriome profile was displayed by the loose STP Mainpuri kapoori. The study further predicted the functional attributes of the prevalent genera by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) algorithm. Genes encoding for nitrate and nitrite reduction and transport enzymes, antibiotic resistance, multi-drug transporters and efflux pumps, secretion of endo- and exotoxin, and other pro-inflammatory molecules were identified. The loose STPs showed the highest level of nitrogen metabolism genes which can contribute to the synthesis of TSNAs. This study reveals the bacteriome of Indian domestic loose STPs that stagger behind in manufacturing and storage stringencies. Our results raise an alarm that the consumption of STPs harboring pathogenic genera can potentially lead to the onset of several oral and systemic diseases. Nevertheless, an in-depth correlation analysis of the microbial diversity of STPs and their elicit impact on consumer health is warranted. KEY POINTS: • Smokeless tobacco harbors bacteria that aid in synthesis of carcinogenic nitrosamines. • Most diverse bacteriome profile was displayed by loose smokeless tobacco products. • Pathogenic genera in these products can harm the oral and systemic health of users.

Comparative and analytical characterization of the oral bacteriome of smokeless tobacco users with oral squamous cell carcinoma

Oral cavity squamous cell carcinoma (OSCC) is the most common type of head and neck cancer worldwide. Smokeless tobacco (SLT) has been well proven for its role in oral carcinogenesis due to the abundance of several carcinogens. However, the role of inhabitant microorganisms in the oral cavity of smokeless tobacco users has not yet been well explored in the context of OSCC. Therefore, the present investigation was conceived to analyze the oral bacteriome of smokeless tobacco users having OSCC (CP group). With the assistance of illumina-based sequencing of bacterial-specific V3 hypervariable region of 16S rDNA gene, 71,969 OTUs (operational taxonomic units) were categorized into 18 phyla and 166 genera. The overall analysis revealed that the oral bacteriome of the patients with OSCC, who were smokeless tobacco users, was significantly different compared to the healthy smokeless tobacco users (HTC group) and non-users (HI users). The appearance of 14 significantly abundant genera [FDR (false discovery rate) adjusted probability value of significance (p value) < 0.05] among the CP group showed the prevalence of tobacco-specific nitrosamines forming bacteria (Staphylococcus, Fusobacterium, and Campylobacter). The functional attributes of the oral bacteriome of the CP group can also be correlated with the genes involved in oncogenesis. This study is the first report on the oral bacteriome of Indian patients with OSCC who were chronic tobacco chewers. The results of the present study will pave the way to understand the influence of smokeless tobacco on the oral bacteriome of OSCC patients. KEY POINTS: • Oral bacteriome of OSCC patients differ from healthy smokeless tobacco (SLT) users and SLT non-users. • Smokeless tobacco influences the oral bacteriome of OSCC group. • Oral bacteriome specific diagnostics may be developed for pre-diagnosis of oral cancer.

Shotgun metagenome sequencing of a Sudanese toombak snuff tobacco: genetic attributes of a high tobacco-specific nitrosamine containing smokeless tobacco product

The most alarming aspect of the Sudanese toombak smokeless tobacco is that it contains high levels of highly toxic tobacco-specific nitrosamines (TSNAs). Understanding the microbiology of toombak is of relevance because TSNAs are an indirect result of microbial-mediated nitrate reductions. We conducted shotgun metagenomic sequencing on a toombak product for which relevant features are presented here. The microbiota was composed of over 99% Bacteria. The most abundant taxa included Actinobacteria, specifically the genera Enteractinococcus and Corynebacterium, while Firmicutes were represented by the family Bacillaceae and the genus Staphylococcus. Selected gene targets were nitrate reduction and transport, antimicrobial resistance, and other genetic transference mechanisms. Canonical nitrate reduction and transport genes (i.e. nar) were found for Enteractinococcus and Corynebacterium while various species of Staphylococcus exhibited a notable number of antimicrobial resistance and genetic transference genes. The nitrate reduction activity of the microbiota in toombak is suspected to be a contributing factor to its high levels of TSNAs. Additionally, the presence of antimicrobial resistance and transference genes could contribute to deleterious effects on oral and gastrointestinal health of the end user. Overall, the high toxicity and increased incidences of cancer and oral disease of toombak users warrants further investigation into the microbiology of toombak.

Characteristics of fungal communities and the sources of mold contamination in mildewed tobacco leaves stored under different climatic conditions

Tobacco mildew is a common postharvest problem caused by fungal growth. It can directly decrease product quality and cause serious economic loss in the tobacco industry. However, the fungal community characteristics of mildewed tobacco leaves and the related influencing factors remain unknown. Here, next-generation sequencing was used to characterize the fungal communities present in mildewed and healthy tobacco leaves stored under three different climatic conditions. Mildewed leaves showed a higher pH and total nitrogen content as well as a lower carbon nitrogen ratio than healthy leaves. Fungal diversity and richness were significantly lower in the mildewed tobacco leaves than in healthy tobacco leaves, with saprophytic fungi such as Xeromyces, Aspergillus, and Wallemia being the dominant molds. Network analysis showed that the complexity, connectivity, and stability of the fungal network were significantly poorer in heavy mildew tobacco leaves than in healthy leaves. NMDS and PERMANOVA analysis showed that the distribution of fungal communities in warehoused tobacco leaves differed significantly across different regions, and temperature and humidity were the key factors affecting these differences. Mildew-causing fungi were significantly enriched in tobacco leaf samples collected in the period between the completion of flue-curing and the start of pre-re-curing. This study demonstrated that mildew is an irreversible process that destroys the balance of the tobacco ecosystem, and that environmental factors play important roles in shaping fungal communities in tobacco leaves.Key points• The diversity and composition of the fungal communities in mildewed tobacco leaves were significantly different from those in healthy tobacco leaves.• Climatic factors may play an important role in shaping fungal communities in tobacco leaves.• Tobacco leaves were most vulnerable to mold contamination between the post-flue-curing and pre-re-curing period.