Methylcellulose Hydrogel with Melissa officinalis Essential Oil as a Potential Treatment for Oral Candidiasis.

Candida spp. are the most prevalent fungi of the human microbiota and are opportunistic pathogens that can cause oral candidiasis. Management of such infections is limited due to the low number of antifungal drugs available, their relatively high toxicity and the emergence of antifungal resistance. Therefore, much interest in the antimicrobial potential of natural compounds has recently been evident. The use of hydrogels in the delivery of biocides has been explored due to their biocompatibility, ease with drug encapsulation, and due to their potential to confer mechanical and structural properties similar to biological tissue. Methylcellulose hydrogels (10% (w/v)) with 1% (v/v) and 2% (v/v) Melissa officinalis oil were synthesised. The rheological properties and gelation time of the hydrogels were evaluated. Antimicrobial action, the antifungal potential and ability to displace Candida were determined. Rheological tests revealed that the hydrogel jellified in three minutes at 37 °C. Loaded hydrogels successfully inhibited Candida albicans growth as evident by zone of inhibition and time-kill assays. A significant reduction in retained C. albicans was demonstrated with the hydrogel at 2% Melissa officinalis concentration. This work demonstrated that an essential oil-loaded hydrogel had the potential to provide a novel antimicrobial therapy for the treatment of oral candidiasis.

Molecular community profiling of the bacterial microbiota associated with denture-related stomatitis.

Denture-associated stomatitis (DS) affects over two-thirds of denture-wearers. DS presents as erythema of the palatal mucosa in areas where denture-surface associated polymicrobial biofilms containing the fungus Candida albicans exist. The contribution of the oral bacterial microbiota toward the infection is unknown. Therefore, this study characterised the bacterial microbiota of sites within the oral cavity to identify potential associations with occurrence of DS. Denture-wearing patients were recruited (denture stomatitis (DS) n = 8; non-denture stomatitis (NoDS) n = 11) and the oral bacterial microbiota of the tongue, palate and denture-fitting surface was characterised using next-generation sequencing. Operational taxonomic units (OTUs) were identified to bacterial genera and species, and presence/absence and relative abundances were examined. A significant (P = 0.007) decrease in the number of OTUs and thus, diversity of the microbiota was observed in tongue samples of DS patients (vs non-DS). The microbiota of denture-fitting surfaces and palatal mucosae were similar. Large differences in the abundance of bacterial genera and species were observed at each sample site, and unique presence/absence of bacteria was noted. Presence/absence and relative abundance of specific bacteria associated with DS warrants further in vitro and in vivo evaluation, particularly as our previous work has shown C. albicans virulence factor modulation by oral bacteria.

Denture-associated biofilm infection in three-dimensional oral mucosal tissue models.

PURPOSE: In vitro analyses of virulence, pathogenicity and associated host cell responses are important components in the study of biofilm infections. The Candida-related infection, denture-associated oral candidosis, affects up to 60 % of denture wearers and manifests as inflammation of palatal tissues contacting the denture-fitting surface. Commercially available three-dimensional tissue models can be used to study infection, but their use is limited for many academic research institutions, primarily because of the substantial purchase costs. The aim of this study was to develop and evaluate the use of in vitro tissue models to assess infections by biofilms on acrylic surfaces through tissue damage and Candida albicans virulence gene expression. METHODOLOGY: In vitro models were compared against commercially available tissue equivalents (keratinocyte-only, SkinEthic; full-thickness, MatTek Corporation). An in vitro keratinocyte-only tissue was produced using a cancer-derived cell line, TR146, and a full-thickness model incorporating primary fibroblasts and immortalised normal oral keratinocytes was also generated. The in vitro full-thickness tissues incorporated keratinocytes and fibroblasts, and have potential for future further development and analysis. RESULTS: Following polymicrobial infection with biofilms on acrylic surfaces, both in-house developed models were shown to provide equivalent results to the SkinEthic and MatTek models in terms of tissue damage: a significant (P<0.05) increase in LDH activity for mixed species biofilms compared to uninfected control, and no significant difference (P>0.05) in the expression of most C. albicans virulence genes when comparing tissue models of the same type. CONCLUSION: Our results confirm the feasibility and suitability of using these alternative in vitro tissue models for such analyses.

IL-34 Suppresses Candida albicans Induced TNFα Production in M1 Macrophages by Downregulating Expression of Dectin-1 and TLR2.

Candida albicans is a fungus that is an opportunistic pathogen of humans. Normally, C. albicans exists as a harmless commensal and does not trigger inflammatory responses by resident macrophages in skin mucosa, which may be caused by a tolerance of skin macrophage to C. albicans. IL-34 is a recently discovered cytokine, constitutively expressed by keratinocytes in the skin. IL-34 binds to the receptor of M-CSF, thereby stimulating tissue macrophage maturation and differentiation. Resident macrophages exhibit phenotypic plasticity and may transform into inflammatory M1 macrophages for immunity or anti-inflammatory M2 macrophages for tissue repair. M1 macrophages produce higher levels of inflammatory cytokines such as TNFα in response to C. albicans stimulation. In this study, it was demonstrated that IL-34 attenuated TNFα production by M1 macrophages challenged with heat killed Candida (HKC). The molecular mechanism of IL-34 mediated suppression of HKC induced TNFα production by M1 macrophages was by the inhibition of M1 macrophage expression of key C. albicans pattern recognition receptors (PPRs), namely, Toll-like receptor (TLR) 2 and Dectin-1. The results of this study indicated that constitutive IL-34 expressed by skin keratinocytes might suppress resident macrophage responses to C. albicans colonisation by maintaining low levels TLR2 and Dectin-1 expression by macrophages.

Effect of progesterone on Candida albicans vaginal pathogenicity.

Candida albicans is responsible for the majority of cases of vulvovaginal candidiasis (VVC), an infection which occurs mainly during the luteal phase of the menstrual cycle or during the pregnancy, when levels of progesterone are elevated. One of the most important candidal virulence factors is the ability to adhere to host surfaces and form biofilms. The aim of this study was to determine the influence of progesterone on C. albicans virulence, namely biofilm formation and colonisation/invasion of a reconstituted human vaginal epithelium (RHVE). Biofilm formation on the RHVE was evaluated by enumeration of culturable cells, total mass quantification and scanning electron microscopy. The capacity of C. albicans strains to invade and colonise the tissue was examined by fluorescence microscopy using species-specific peptide nucleic acid (PNA) probe hybridisation, and quantitatively evaluated by RT-PCR Candida quantification methodology. Furthermore, gene (BCR1 and HWP1) expression of biofilm and RHVE-colonising cells was evaluated by quantitative RT-PCR. Results confirmed that progesterone reduced the capacity of C. albicans strains to form biofilms and to colonise and invade RHVE. Additionally, it was demonstrated that progesterone decreased expression of BCR1 and HWP1, which are important virulence determinants of C. albicans. In conclusion, it was evident that progesterone can have a major influence on C. albicans pathogenicity on vaginal epithelial cells and may partly explain susceptibility of women to VVC at different stages of the menstrual cycle.

Comparative adherence of Candida albicans and Candida dubliniensis to human buccal epithelial cells and extracellular matrix proteins.

Candida albicans and Candida dubliniensis are very closely related pathogenic yeast species. Despite their close relationship, C. albicans is a far more successful colonizer and pathogen of humans. The purpose of this study was to determine if the disparity in the virulence of the two species is attributed to differences in their ability to adhere to human buccal epithelial cells (BECs) and/or extracellular matrix proteins. When grown overnight at 30°C in yeast extract peptone dextrose, genotype 1 C. dubliniensis isolates were found to be significantly more adherent to human BECs than C. albicans or C. dubliniensis genotypes 2-4 (P < 0.001). However, when the yeast cells were grown at 37°C, no significant difference between the adhesion of C. dubliniensis genotype 1 and C. albicans to human BECs was observed, and C. dubliniensis genotype 1 and C. albicans adhered to BECs in significantly greater numbers than the other C. dubliniensis genotypes (P < 0.001). Using surface plasmon resonance analysis, C. dubliniensis isolates were found to adhere in significantly greater numbers than C. albicans to type I and IV collagen, fibronectin, laminin, vitronectin, and proline-rich peptides. These data suggest that C. albicans is not more adherent to epithelial cells or matrix proteins than C. dubliniensis and therefore other factors must contribute to the greater levels of virulence exhibited by C. albicans.

Lipopolysaccharide-induced M2 to M1 macrophage transformation for IL-12p70 production is blocked by Candida albicans mediated up-regulation of EBI3 expression.

Macrophages are heterogeneous cell populations that are present in all tissues. Macrophages can be divided into classically activated inflammatory macrophages (M1) and alternatively activated anti-inflammatory macrophages (M2). It has been generally accepted that M1 macrophages are polarised in an inflammatory environment to produce pro-inflammatory cytokines, whilst M2 macrophages are involved in anti-inflammation and aid tissue repair in wound healing. Bacterial endotoxin (lipopolysaccharide; LPS) is a potent factor in infection, which induces M1 macrophages resulting in higher levels of iNOS, TNFα and IL-12p70 which dictate inflammatory T cell responses. M2 macrophages can be transformed into M1 macrophages following LPS stimulation to promote inflammation. Candida albicans is a commensal fungal microorganism, which has been suggested to induce immune tolerance; however, the mechanism of C. albicans-induced immune tolerance has not been investigated in detail. IL-35 is a recently identified anti-inflammatory cytokine which is a heterodimeric protein consisting of the Epstein-Barr virus-induced gene 3 (EBI3) and IL-12p35. IL-35 shares the protein subunit p35, with IL-12p70. IL-12p70 is the most potent cytokine to induce Th1 responses during inflammation. In this study, we demonstrate that heat-killed C. albicans (HKC) strongly suppressed LPS-induced IL-12p70 production in M2 macrophages. Candida albicans induced a high level of EBI3 expression in M2 macrophages, which served as a mechanism for IL-12p70 suppression by competitive binding of the common protein subunit (p35) of IL-35 and IL-12p70. To demonstrate that EBI3 expression had the ability to block IL-12p70 production intracellularly, a Chinese Hamster Ovary (CHO) cell line with biscistronic expression of IL-12p40 and p35 was constructed, followed by ectopic over-expression of EBI3. The over-expression of EBI3 in the IL-12p70 producing cell line effectively suppressed IL-12p70 production. IL-35 secretion was also detected in the cell line, with suppressed IL-12p70 production by immune-precipitation Western blotting. However, this secretion was not evident in M2 macrophages following stimulation by HKC. This can be explained by the constitutive expression of IL-35 receptors (gp130 and IL-12Rß2) in M2 macrophages for cytokine consumption. Our results have indicated that C. albicans can suppress host inflammatory responses in mucosal skin by suppressing LPS-induced IL-12p70 production. Lower IL-12p70 production may avoid an unnecessary Th1 response in order to retain immune tolerance, which may be one of the mechanisms by which C. albicans achieves a successful commensal lifestyle without having a detrimental effect on the host's health.

Differential cellular and microbial responses to nano-/micron-scale titanium surface roughness induced by hydrogen peroxide treatment.

This study investigated the effects of combined titanium nano-/micron-scale roughness, induced by hydrogen peroxide pre-treatments, on bone marrow stromal cell responses and Porphyromonas gingivalis adherence in vitro. Untreated surfaces exhibited nano-scale features, while hydrogen peroxide treatments promoted increased nano-/micron-scale roughness. Bone marrow stromal cell attachment and proliferation were maintained with 6 h and 24 h treatments, but significantly decreased on 1-week and 4-week-treated surfaces. Bone marrow stromal cells on 6 h-4 week-treated titanium demonstrated enhanced osteogenic differentiation versus untreated surfaces. P. gingivalis adherence was significantly increased on 24 h-4 week surfaces. Results suggest that 6 h but less than 24 h treatments maintain or promote bone marrow stromal cell responses while minimizing microbial adherence, potentially enhancing titanium surface bio-activation for osseointegration.

Candida glabrata and Candida albicans co-infection of an in vitro oral epithelium.

BACKGROUND: Candida albicans is regarded as the leading of candidosis. However, Candida glabrata has emerged as an important pathogen of oral mucosa, occurring both singly or in mixed species infections, often with C. albicans. Compared with C. albicans, little is known about the role of C. glabrata in oral infection. The aim of this study was to examine single and mixed species infection of oral epithelium involving C. glabrata and establish its ability to invade and damage tissue. METHODS: A reconstituted human oral epithelium (RHOE) was infected only with C. glabrata, or simultaneously with C. glabrata and C. albicans. The ability of both species to invade the tissue was examined using species specific peptide nucleic acid (PNA) probe hybridization and confocal laser scanning microscopy. Epithelial damage was assessed by measuring lactate dehydrogenase (LDH) activity. RESULTS: Candida glabrata strains were able to colonize the RHOE, in a strain dependent manner. Candida glabrata single infection after 12 h, generally revealed no invasion of the RHOE, which contrasted with extensive tissue invasion demonstrated by C. albicans. Mixed infection showed that C. albicans enhanced the invasiveness of C. glabrata, and led to increased LDH release by the RHOE, which paralleled the observed histological damage. CONCLUSIONS: The results obtained demonstrating enhanced invasion and increased tissue damage caused by mixed C. glabrata and C. albicans infections have important clinical significance and highlight the need to identify Candida species involved in oral candidosis.

Effects of atomoxetine on self-reported high-risk behaviors and health-related quality of life in adolescents with ADHD.

OBJECTIVE: This study measured the effects of atomoxetine HCl on high-risk behaviors and health-related quality of life in adolescents with attention-deficit/hyperactivity disorder (ADHD), using a subgroup analysis of data from a previous clinical trial. RESEARCH DESIGN AND METHODS: In the base study, which was conducted at 26 sites in the United States, patients ages 13-16 years were randomized in a double-blind manner to atomoxetine treatment by one of two dose titration schedules for 8 weeks. Patients who responded to treatment were rerandomized to atomoxetine at a daily dose of 0.8 or 1.4 mg/kg for 40 weeks. Patients in the highest-risk quartile for each category of behavior or domain were included and the dosing groups combined. MAIN OUTCOME MEASURES: Efficacy measures included the Youth Risk Behavior Surveillance (YRBS) and Child Health and Illness Profile - Adolescent Edition (CHIP-AE). The YRBS has six categories of behavior, and the CHIP-AE has six domains. Data for mean change from baseline were analyzed using a last-observation-carried-forward analysis. RESULTS: A total of 267 patients were randomized, but the high-risk subgroup analyzed in the present study was much smaller (range of n = 5-68 per group). YRBS scores for tobacco use, unhealthful dietary behaviors, inadequate physical activity, and behaviors contributing to unintentional injuries showed statistically significant improvements (p < 0.05) by atomoxetine treatment at Week 8. At the end of the 40-week maintenance period, unhealthful dietary behaviors, inadequate physical activity, and behaviors contributing to unintentional injuries continued to show statistically significant improvements (p < 0.001). When the highest-risk quartile of the CHIP-AE data was analyzed, there were statistically significant improvements on all six domains after atomoxetine treatment at 8 weeks (p < 0.001) and on five of the six domains at 40 weeks (p < or = 0.01). CONCLUSIONS: Atomoxetine improved self-reported high-risk behaviors and overall health-related quality of life in adolescents with ADHD. Potential limitations of this study include small sample sizes and the fact that it involved a subgroup analysis, which is by nature hypothesis-generating. Further, well-controlled, prospective studies in larger and more heterogeneous ADHD populations, including older patients, are warranted to confirm or reject these findings.

The multiple sclerosis whole blood mRNA transcriptome and genetic associations indicate dysregulation of specific T cell pathways in pathogenesis.

Multiple sclerosis (MS) is an autoimmune disease with a genetic component, caused at least in part by aberrant lymphocyte activity. The whole blood mRNA transcriptome was measured for 99 untreated MS patients: 43 primary progressive MS, 20 secondary progressive MS, 36 relapsing remitting MS and 45 age-matched healthy controls. The ANZgene Multiple Sclerosis Genetics Consortium genotyped more than 300 000 SNPs for 115 of these samples. Transcription from genes on translational regulation, oxidative phosphorylation, immune synapse and antigen presentation pathways was markedly increased in all forms of MS. Expression of genes tagging T cells was also upregulated (P < 10(-12)) in MS. A T cell gene signature predicts disease state with a concordance index of 0.79 with age and gender as co-variables, but the signature is not associated with clinical course or disability. The ANZgene genome wide association screen identified two novel regions with genome wide significance: one encoding the T cell co-stimulatory molecule, CD40; the other a region on chromosome 12q13-14. The CD40 haplotype associated with increased MS susceptibility has decreased gene expression in MS (P < 0.0007). The second MS susceptibility region includes 17 genes on 12q13-14 in tight linkage disequilibrium. Of these, only 13 are expressed in leukocytes, and of these the expression of one, FAM119B, is much lower in the susceptibility haplotype (P < 10(-14)). Overall, these data indicate dysregulation of T cells can be detected in the whole blood of untreated MS patients, and supports targeting of activated T cells in therapy for all forms of MS.

Managing earthworm casts (Oligochaeta: Lumbricidae) in turfgrass using a natural byproduct of tea oil (Camellia sp.) manufacture.

BACKGROUND: Earthworm casts are a worldwide problem on golf courses and sports fields when they disrupt the playability, aesthetics and maintenance of closely mowed playing surfaces. Currently, no pesticides are labeled for earthworms in the United States. Tea seed pellets (TSPs), a saponin-rich byproduct of Camellia oleifera Abel oil manufacture, were tested for expelling earthworms and reducing casts on creeping bentgrass turf. The fate of expelled worms, methods for removing them and impacts on pest and beneficial arthropods were also evaluated. RESULTS: Application of TSPs at 2.93 kg 100 m(-2), followed by irrigation, quickly expelled earthworms from the soil. A single application reduced casts by 80-95% for at least 5 weeks. Mowing or sweeping removed expelled earthworms from putting green surfaces. Most expelled earthworms burrowed down when transferred to untreated turf, but few survived. Bioassay-guided fractionation confirmed the vermicidal activity results from a mix of saponins. TSPs did not reduce the abundance of beneficial soil arthropods, nor did they control black cutworms or white grubs in treated turf. CONCLUSION: TSPs are an effective botanical vermicide that could be useful for selectively managing earthworm casts on closely mowed turfgrass. They might also be used to suppress earthworms in grassy strips alongside runways to reduce bird strike hazard at airports.

Detection and identification of specific bacteria in wound biofilms using peptide nucleic acid fluorescent in situ hybridization (PNA FISH).

Biofilms provide a reservoir of potentially infectious micro-organisms that are resistant to antimicrobial agents, and their importance in the failure of medical devices and chronic inflammatory conditions is increasingly being recognized. Particular research interest exists in the association of biofilms with wound infection and non-healing, i.e. chronic wounds. In this study, fluorescent in situ hybridization (FISH) was used in combination with confocal laser scanning microscopy (CLSM) to detect and characterize the spatial distribution of biofilm-forming bacteria which predominate within human chronic skin wounds (Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus sp. and Micrococcus sp.). In vitro biofilms were prepared using a constant-depth film fermenter and a reconstituted human epidermis model. In vivo biofilms were also studied using biopsy samples from non-infected chronic venous leg ulcers. The specificity of peptide nucleic acid (PNA) probes for the target organisms was confirmed using mixed preparations of planktonic bacteria and multiplex PNA probing. Identification and location of individual bacterial species within multi-species biofilms demonstrated that P. aeruginosa was predominant. CLSM revealed clustering of individual species within mixed-species biofilms. FISH analysis of archive chronic wound biopsy sections showed bacterial presence and allowed bacterial load to be determined. The application of this standardized procedure makes available an assay for identification of single- or multi-species bacterial populations in tissue biopsies. The technique provides a reliable tool to study bacterial biofilm formation and offers an approach to assess targeted biofilm disruption strategies in vivo.

Association of oral yeast carriage with specific host factors and altered mouth sensation.

OBJECTIVES: The aim of this study was to determine if there was a significant association between the presence of altered mouth and taste sensations with oral carriage of yeasts and to assess the factors that influence the yeast carriage. STUDY DESIGN: The oral and dental status including unstimulated (USFR) and stimulated (SSFR) whole salivary flow rates of a total of 509 subjects was recorded. Saliva specimens were collected for microbiologic examination. Multiple logistic regression analysis was performed to identify any factors that were significantly associated with the prevalence of oral yeasts. RESULTS: Old age, clinical signs of oral dryness, denture wearing, and a reduction in USFR increased the prevalence of yeasts, whereas patient gender, levels of dentition, the sensation of dry or burning mouth, taste disorders, and SSFR were not associated with increased prevalence of oral yeasts. CONCLUSIONS: An increased prevalence of oral yeasts was not found to relate to changes in mouth sensation alone. Other factors, most notably patient age, the wearing of dentures, clinical signs of oral dryness, and salivary flow rate under rest conditions, were, however, found to be closely associated with oral yeast carriage.

Proteinase activity of prevotella species associated with oral purulent infection.

Prevotella intermedia and Prevotella nigrescens are often regarded as principal causes of acute dentoalveolar infection; however, other species within the genus are also known to be associated with such infection. The aim of this study was to determine the in vitro proteolytic activity of these different Prevotella species that have been implicated with dentoalveolar infection. A total of 234 strains were obtained from pus specimens from dentoalveolar infection and from the plaque of healthy volunteers. Prevotella loescheii, Prevotella oralis, Prevotella melaninogenica, Prevotella buccae, and Prevotella denticola were all shown to have a proteolytic activity (8.5-10.5 x 10(-8) A-units) lower than that of P. intermedia and P. nigrescens (21.1-23.5 x 10(-8) A-units). In the case of P. loescheii, P. melaninogenica, and P. intermedia, the level of proteolytic activity for clinical strains was significantly (P < 0.05) higher than that recorded for commensal strains. Proteolytic activity for all species of Prevotella examined was inhibited by N-ethylmaleimide and phenymethylsulfonyl fluoride. This study suggests that Prevotella species associated with oral purulent infection produce cysteine and serine proteinases and that in certain species of Prevotella, the strains involved in infection exhibit higher proteolytic activity when compared with strains from healthy sites.

Evaluation of the recurrence of denture stomatitis and Candida colonization in a small group of patients who received itraconazole.

OBJECTIVES: The aim of the study was to determine the recurrence rate of denture stomatitis and persistence of Candida in 22 patients (5 male and 17 female, mean age 71 years) over a 3-year period. STUDY DESIGN: Denture hygiene practice, denture cleanliness, and the presence of palatal erythema were assessed for each patient at the start of the study (baseline). The oral cavity was sampled for yeasts by imprint culture and denture discs. Ten patients received a capsular form of itraconazole (100 mg twice daily for 15 days) and 12 patients were provided with 100 mg of itraconazole in the form of a mouthwash (10 mL twice daily), which was then swallowed. No further antifungal treatment was administered to any of the patients. Clinical and microbiological assessments were repeated for each patient at 6 months and 3 years after the original appointment. Yeasts were identified by colony color on CHROMagar Candida, germ-tube formation, and API-32C profiling. Selected isolates were then typed by inter-repeat polymerase chain reaction (IR PCR). RESULTS: Candida albicans was isolated at baseline from all patients either alone (12 patients) or in combination with another species (10 patients). Other yeast species recovered were C glabrata (5 patients), C tropicalis (1 patient), C guilliermondii (1 patient), C krusei (1 patient), C parapsilosis (1 patient), C kefyr (1 patient), and Saccharomyces cerevisiae (2 patients). Candida albicans and/or C glabrata were recovered from 11 of the 22 patients after 6 months or 3 years. A complete and consistent change of yeast species from baseline was observed in 6 patients after 6 months and at 3 years. The remaining 5 patients were yeast-free at the follow-up assessments. PCR fingerprinting of C albicans and C glabrata indicated strain persistence over 6 months in 10 patients and in 4 patients after 3 years. A switch in strain type occurred for 1 patient after 6 months and for 3 patients after 3 years. CONCLUSIONS: The recurrence of denture stomatitis in patients who maintained a high standard of denture cleanliness was low. Although itraconazole was beneficial in reducing the fungal load, there may be strain persistence or subsequent recolonization of the oral cavity by a broader range of potentially less sensitive yeast species.

Host pathogen interaction and the development of oral lesions.

The aetiologies of oral ulceration, disseminated interstitial lymphocytosis syndrome and oral lymphomas have been reviewed, with emphasis on the role of HIV infection in the primary causation or modification of the presentation of these entities. There is a paucity of evidence to explain why oral ulceration is so severe in HIV infection, and why major ulceration affects the oropharynx. A number of mechanisms have been proposed to account for the development of lymphomas in patients with HIV infection, including a genetic predisposition, decreased immunosurveillance due to HIV infection, alteration of endothelial cell function and dysregulation of cytokine networks. From this review, it was concluded that there is a need for a prospective multicentre study, to elucidate the aetiological mechanisms involved in lymphomas of the oral regions in this patient group. It was concluded that, although there is anecdotal evidence implicating tobacco use in the aetiology of the lesions reviewed, this is insufficient to allow definitive statements to be made and further systematic evaluation is indicated.