Daily variation of oral malodour and related factors in community-dwelling elderly Thai

doi: 10.1111/j.1741‐2358.2011.00593.x Daily variation of oral malodour and related factors in community‐dwelling elderly Thai Objectives: The purposes of this study were (i) to estimate the prevalence of oral malodour, (ii) to evaluate the daily variation of oral malodour and (iii) to assess associations of volatile sulphur compound (VSC) concentrations with socio‐demographics, health behaviours and oral health status in community‐dwelling elderly Thai. Methods: The subjects were 428 dentate elderly people (67.6 ± 5.6 years) living in Phitsaulok, Thailand. Information on their socio‐demographics, general health and health behaviours was obtained by a questionnaire. Their dental condition, periodontal status and tongue coating were clinically examined. Their flow rates and the pH of unstimulated saliva were also assessed. Oral malodour was measured at four different times of day using an Oral Chroma?. Results: The proportions of subjects diagnosed with oral malodour using the thresholds of H₂S, CH₃SH and (CH₃)₂S were 60.5%, 62.9% and 80.7%, respectively. Concentrations of H₂S showed significant daily variation. Linear regression analysis demonstrated the following significant associations: (i) oral malodour from H₂S and thickness of the tongue coating, (ii) oral malodour from CH₃SH and periodontal pocket depth of 5 mm or more and the presence of gingival bleeding and (iii) oral malodour from (CH₃)₂S and systemic disease, medications and thickness of the tongue coating. Discussion: Oral malodour was shown to be prevalent among the elderly. Daily variation was observed in the concentration of H₂S. Tongue coating, periodontal disease, systemic diseases and medications were related to oral malodour. Therefore, these factors should be taken into consideration in oral malodour treatment and prevention programmes for the elderly.     

Oral microbial flora and oral malodour of the institutionalised elderly in Japan

Objectives: To determine the oral health status, especially the level of oral microbial flora and oral malodour, of institutionalised elderly people compared with non‐institutionalised elderly people. Setting: Three institutions and numerous private homes. Subjects: 56 institutionalised and 56 non‐institutionalised elderly people. Main Outcome Measures: Institutionalised elderly people had higher levels of Candida, staphylococci, and oral malodour. Results: Institutionalised elderly people had a higher level of Candida in denture wearers, and a higher level of staphylococci and oral malodour compared with the non‐institutionalised elderly. Conclusion: The institutionalised elderly have a higher risk of opportunistic infections and oral health care should be improved to protect them from these infections and to reduce oral malodour.     

Photosynthetic rates of citronella and lemongrass

Ten selections of citronella (Cymbopogon nardus [L.] Rendle) were grown at 32/27, 27/21, or 15/10 C day/night temperatures, and plants from three populations of lemongrass (Cymbopogon citratus [D.C.] Stapf from Japan or Sri Lanka and Cymbopogon flexuosus [D.C.] Stapf from India) were grown at 8- or 15-hour photoperiods. Net photosynthetic rates of mature leaves were measured in a controlled environment at 25 C and 260 microeinsteins per meter² per second. Rates declined with increasing leaf age, and from the tip to the base of the leaf blade. Rates for citronella leaves grown at 15/10 C were extremely low for all selections. Highest rates of net photosynthesis were recorded for four selections grown at 27/21 C and for two selections grown at 32/27 C. Lemongrass grown at 8-hour photoperiod had higher photosynthetic rates than that grown at 15-hour photoperiod.     

A preliminary study of the effect of probiotic Streptococcus salivarius K12 on oral malodour parameters

AIMS: To determine whether dosing with bacteriocin-producing Streptococcus salivarius following an antimicrobial mouthwash effects a change in oral malodour parameters and in the composition of the oral microbiota of subjects with halitosis. MATERIALS AND RESULTS: Twenty-three subjects with halitosis undertook a 3-day regimen of chlorhexidine (CHX) mouth rinsing, followed at intervals by the use of lozenges containing either S. salivarius K12 or placebo. Assessment of the subjects' volatile sulphur compound (VSC) levels 1 week after treatment initiation showed that 85% of the K12-treated group and 30% of the placebo group had substantial (>100 ppb) reductions. The bacterial composition of the saliva was monitored by culture and PCR-denaturing gradient gel electrophoresis (PCR-DGGE). Changes in the PCR-DGGE profiles occurred in most subjects following K12 treatment. In vitro testing showed that S. salivarius K12 suppressed the growth of black-pigmented bacteria in saliva samples and also in various reference strains of bacteria implicated in halitosis. CONCLUSIONS: Administration of bacteriocin-producing S. salivarius after an oral antimicrobial mouthwash reduces oral VSC levels. SIGNIFICANCE AND IMPACT OF THE STUDY: The outcome of this preliminary study indicates that the replacement of bacteria implicated in halitosis by colonization with competitive bacteria such as S. salivarius K12 may provide an effective strategy to reduce the severity of halitosis.     

Carbon dioxide compensation values in citronella and lemongrass

Carbon dioxide compensation values of mature leaves from 10 selections of citronella (Cymbopogon nardus [L.] Rendle) grown at 32/27 or 27/21 C day/night temperatures and three strains of lemongrass (Cymbopogon citratus [D.C.] Stapf. and Cymbopogon flexuosus [D.C.] Stapf.) grown at 8- or 15-hour photoperiods were measured in a controlled environment at 25 C. All leaves had low compensation values but citronella varied from 1.3 to 9.7 μl/liter and lemongrass from 0.7 to 3.5 μl/liter. Lower growing temperature generally resulted in lower compensation values for citronella but there was no consistent photoperiod effect on lemongrass.     

In vitro biofilm model for studying tongue flora and malodour

AIMS: To develop a perfusion biofilm system to model tongue biofilm microflora and their physiological response to sulfur-containing substrates (S-substrates) in terms of volatile sulfide compound (VSC) production. METHODS AND RESULTS: Tongue-scrape inocula were used to establish in vitro perfusion biofilms which were examined in terms of ecological composition using culture-dependent and independent (PCR-DGGE) approaches. VSC-specific activity of cells was measured by a cell suspension assay, using a portable industrial sulfide monitor which was also used to monitor VSC production from biofilms in situ. Quasi steady states were achieved by 48 h and continued to 96 h. The mean (+/-SEM) growth rate for 72-h biofilms (n=4) was micro=0.014 h(-1) (+/-0.005 h(-1)). Comparison of biofilms, perfusate and original inoculum showed their ecological composition to be similar (Pearson coefficient>0.64). Perfusate and biofilm cells derived from the same condition (co-sampled) were equivalent with regard to VSC-specific activities which were up-regulated in the presence of S-substrates. CONCLUSIONS: The model maintained a stable tongue microcosm suitable for studying VSC production; biofilm growth in the presence of S-substrates up-regulated VSC activity. SIGNIFICANCE AND IMPACT OF THE STUDY: The method is apt for studying ecological and physiological aspects of oral biofilms and could be useful for screening inhibitory agents.     

Heritability estimates of citral content in East Indian lemongrass

Summary Citral content in oil obtained from 80 representative clones, chosen randomly from a population raised from open-pollinated seeds of clonally propagated East Indian lemongrass variety SD-68 and their half-sib progenies was estimated by gas chromatography. Heritability estimates were determined by variance component and parent-offspring regression analyses. Broad-sense heritability was 0.49 while narrow sense heritabilities by variance and regression analyses were 0.37 and 0.24, respectively. Phenotypic and genotypic correlations between citral content in oil and oil content were very low both among the parental clones (-0.01 and -0.01, respectively) and among their progenies (0.13 and 0.08, respectively) indicating that selection for either of these traits would not have much effect on the other.     

Alleviation of salt stress in lemongrass by salicylic acid

Soil salinity is one of the key factors adversely affecting the growth, yield, and quality of crops. A pot study was conducted to find out whether exogenous application of salicylic acid could ameliorate the adverse effect of salinity in lemongrass (Cymbopogon flexuosus Steud. Wats.). Two Cymbopogon varieties, Krishna and Neema, were used in the study. Three salinity levels, viz, 50, 100, and 150 mM of NaCl, were applied to 30-day-old plants. Salicylic acid (SA) was applied as foliar spray at 10^?5 M concentration. Totally, six SA-sprays were carried out at 10-day intervals, following the first spray at 30 days after sowing. The growth parameters were progressively reduced with the increase in salinity level; however, growth inhibition was significantly reduced by the foliar application of SA. With the increase in salt stress, a gradual decrease in the activities of carbonic anhydrase and nitrate reductase was observed in both the varieties. SA-treatment not only ameliorated the adverse effects of NaCl but also showed a significant improvement in the activities of these enzymes compared with the untreated stressed-plants. The plants supplemented with NaCl exhibited a significant increase in electrolyte leakage, proline content, and phosphoenol pyruvate carboxylase activity. Content and yield of essential oil was also significantly decreased in plants that received salinity levels; however, SA overcame the unfavorable effects of salinity stress to a considerable extent. Lemongrass variety Krishna was found to be more adapted to salt stress than Neema, as indicated by the overall performance of the two varieties under salt conditions.     

The potential impact of washing machines on laundry malodour generation

A multidisciplinary approach has been adopted to investigate and identify the source of malodour in washing machines and the potential for cross‐contamination of laundry. Four washing machines were olfactively graded, and the number of colony‐forming units (CFUs) bacteria was determined in four specific locations. Then, samples of terry‐towel and fleece were washed, without the use of detergent, in the machines, and the occurrence of malodour over a 52‐h period was assessed. Analysis of the scrapings from the four locations in the two malodorous machines identified a plethora of volatile organic compounds (VOCs) by either olfactory detection or mass spectral identification post‐gas chromatographic separation. In addition, microbiological analysis from the swabs from the four locations within all four washing machines was carried out. Quantitative analysis of VOCs from 66 microbiological isolates from either the washing machines or fabrics was carried out. In total, 10 VOCs were identified: dimethyl disulfide, 3‐methyl‐1‐butanol, 2,4‐dithiapentane, dimethyl trisulfide, 2‐tridecanone, indole, 2‐phenylethanol, isovaleric acid, isobutyric acid and 1‐undecene.

Significance and Impact of the Study

The data presented in this study highlight that the environment and odour of the washing machine can lead to cross‐contamination of laundry.     

Microbial pathways leading to steroidal malodour in the axilla

Odorous steroids, specifically the 16-androstenes, 5alpha-androstenol and 5alpha-androstenone, are widely accepted as being contributors to underarm odour, but the precursors and pathways to these odorous steroids were unclear. This study demonstrated that the axillary microflora could only generate odorous 16-androstenes from precursors that already contain the C16 double bond, such as 5,16-androstadien-3-ol and 4,16-androstadien-3-one. In incubations containing 5,16-androstadien-3-ol, mixed populations of Corynebacterium spp., isolated from the axilla, could generate many different 16-androstene metabolites, several of which were odorous. Isolation of individual Corynebacterium strains, followed by pure culture incubations with 5,16-androstadien-3-ol, revealed organisms capable of efficient, rapid reactions. However, no single isolate could carry out a full complement of the observed biotransformations. 16-Androstene metabolites were identified by gas chromatography-mass spectrometry (GC-MS), either by comparison with known standards, or by prediction from molecular ion and fragmentation patterns. Based on detection of these metabolites, a metabolic map for axillary corynebacterial 16-androstene biotransformations was proposed, detailing potential enzyme activities. In summary, the formerly implicated 4,16-androstadien-3-one, 5alpha-androstenone and 5alpha-androstenol were detected, along with previously unreported hydroxy- and keto-substituted 16-androstenes, 16-androstatrienones and 16-androstatrienols. Additionally, many other metabolites with steroidal fragmentation patterns were present, but have remained unidentified.A key observation was that very low prevalences of microorganisms capable of biotransforming 16-androstenes were present on skin. For example, from a panel of 21 individuals, only 4 of 18 mixed populations of corynebacteria, and only 4 of 45 Corynebacterium isolates, could biotransform 5,16-androstadien-3-ol.This study has increased understanding of the metabolic pathways involved in steroidal malodour formation, and has demonstrated that the biotransformations are more complex than previously anticipated. However, it is clear that further research is required, both to assess the level of contribution of 16-androstenes to underarm odour, and to further elucidate the pathways and odour molecules formed by corynebacteria.     

Fatty acid metabolism by cutaneous bacteria and its role in axillary malodour

It is generally accepted that short (C₂-C₅) and medium (C₆-C₁₁) chain volatile fatty acids (VFAs) are among the primary causal molecules of axillary malodour. It is also widely acknowledged that malodour generation is attributable to the biotransformation of odourless natural secretions, into volatile odorous products, by cutaneous bacteria. However, little information is available on the biochemical origins of VFAs on axillary skin. In these studies, assay systems were developed to investigate the generation of VFAs from lipid substrates readily available to the bacteria resident on axillary skin. A major route to short and medium chain VFAs in the axilla was shown to be the partial catabolism of structurally unusual (e.g. methyl-branched) longer chain fatty acids by a previously uncharacterized sub-group of the Corynebacterium genus, corynebacteria (A). In contrast, corynebacteria (B) are incapable of growth on fatty acid. Structurally unusual fatty acids originate from the triacylglycerol component of sebum, and probably also apocrine sweat, by the action of bacterial lipases. Interestingly, VFA formation in the axilla is a dynamic process, with some cutaneous microorganisms, specifically micrococci and brevibacteria, capable of fully catabolizing these odorants. The results of these studies provide new understanding on the biochemical origins of VFA-based axillary malodour.     

Salicylic acid-induced physiological and biochemical changes in lemongrass varieties under water stress

Abstract

Salicylic acid (SA) treatment reduces the damaging action by water deficit on growth and accelerates a restoration of growth processes. The aim of the present work was to study the physiological and biochemical alteration induced by SA in lemongrass plants under stress conditions. Therefore, a pot culture experiment was conducted to test whether SA application at concentration of (10^?5 M) through foliar spray could protect lemongrass (Cymbopogon flexuosus Steud. Wats.) varieties (Neema and Krishna), subjected to drought stress on the basis of growth parameters and biochemical constituents, proline metabolism and quality attributes including citral content. The treatments were as follows: (i) 100% FC + 0 SA; (ii) 75% FC + 0 SA; (iii) 50% FC + 0 SA; (iv) 75% FC + 10^?5 M SA; and (v) 50% FC + 10^?5 M SA. The growth parameters were significantly reduced under the applied water stress levels; however, foliar application of salicylic acid (10^?5 M) improved the growth parameters in stress-affected plants. The plants under water stress exhibited a significant increase in activities of nitrate reductase and carbonic anhydrase, and electrolyte leakage, proline content, free amino acid and in PEP carboxylase activity. Content and yield of essential oil also significantly decreased in plants that faced water stress. Thus, it was concluded that variety Neema is the more tolerant variety as compared to Krishna on the basis of content and oil yield and well adapted to drought stress conditions.     

Antimicrobial activity of lemongrass oil against Salmonella enterica on organic leafy greens

Aims: We investigated the antimicrobial effectiveness of lemongrass essential oil on organic leafy greens, romaine and iceberg lettuces and mature and baby spinach, inoculated with Salmonella Newport. The influences of exposure times and abuse temperatures on bacterial survival were also investigated. Methods and Results: Leaf samples were washed, inoculated with Salm. Newport (6‐log CFU ml^?1) and dried. Inoculated leaves were immersed in solutions containing 0·1, 0·3 or 0·5% lemongrass oil in phosphate‐buffered saline for 1 or 2 min and then individually incubated at 4 or 8°C. Samples were taken at day 0, 1 and 3 for the enumeration of survivors. Compared to the PBS control, romaine and iceberg lettuces, and mature and baby spinach samples showed between 0·6–1·5‐log, 0·5–4·3‐log, 0·5–2·5‐log and 0·5–2·2‐log CFU g^?1 reductions in Salm. Newport by day 3, respectively. Conclusions: The antimicrobial activity of lemongrass oil against Salm. Newport was concentration and time dependent. The antimicrobial activity increased with exposure time; iceberg samples treated for 2 min generally showed greater reductions (P < 0·05) than those treated for 1 min (c. 1‐log reduction difference for 0·3 and 0·5% treatments). Few samples showed a difference between refrigeration and abuse temperatures. Significance and Impact of the Study: This study demonstrates the potential of lemongrass oil solutions to inactivate Salm. Newport on organic leafy greens.     

Determination of antibacterial activity of vacuum distillation fractions of lemongrass essential oil

Essential oils are natural substances composed of terpenoids and phenylpropanoid molecules that have many biological activities. Because of their activity, essential oils are widely used in foods, cosmetics, and pharmaceutical products, but new applications of such mixtures are still dependent on separation processes that are able to produce compounds with specific standardized and reproducible compositions. This work studies the fractionation of lemongrass essential oil by vacuum distillation with the goal of obtaining an antimicrobial fraction that acts against Salmonella choleraesuis, Pseudomonas aeruginosa and Staphylococcus aureus. The samples were analyzed by gas chromatography–mass spectrometry and evaluated for antimicrobial activity using the indirect bioautography method and minimum inhibitory concentrations. Vacuum distillation was found to be an efficient method for obtaining distinct fractions with increased antimicrobial activity. The fractions that showed the best response against the three microorganisms tested were F3b, F3a1, F2, F3a2 and F1, with the most effective being F3a2, which also presented the highest yield.     

Antibiofilm activity and post antifungal effect of lemongrass oil on clinical Candida dubliniensis isolate

Candidal infections are often difficult to eradicate due to the resistance of biofilms to antifungal agents. This study aimed at determining the effects of lemongrass (Cymbopogon citratus DC) oil against Candida dubliniensis in both planktonic and biofilms form. The results from broth microdilution method revealed that the minimum inhibitory and minimum fungicidal concentration of lemongrass oil on C. dubliniensis were 0.43 and 0.86 mg/ml, respectively. Employing a formazan salt (XTT tetrazolium) reduction assay for biofilm study, the results showed that the average percentage (mean ± SD) inhibition of lemongrass oil (0.43 mg/ml) on biofilm formation was 91.57 ± 1.31%, while it exhibited more than 80% killing activity against C. dubliniensis in biofilm at concentrations of 1.7 mg/ml. In addition, a significant reduction (P = 0.03) of candidal adhesion to acrylic occurred after a 15 min exposure to 1.7 mg/ml of lemongrass oil. Moreover, limited exposure of yeasts to lemongrass oil at subcidal concentration can suppress growth for more than 24 h. Altogether, the results obtained indicate that lemongrass oil possessed antifungal and antibiofilm activities and could modulate candidal colonization. Therefore, the efficacy of lemongrass oil merits further development of this agent for the therapy of oral candidiasis.     

Effects of lemongrass oil on the morphological characteristics and peptidoglycan synthesis of Escherichia coli cells

The antibacterial effect of lemongrass oil, obtained from the aerial part of Cymbopogon citratus, on cells of Escherichia coli was investigated by electron microscopy and by measuring cell wall formation. Two strains of E. coli K-12 were used, one of which required diaminopimelic acid in the growth medium for its murein formation. Lemongrass oil was found to elicit morphological changes like filamentation, inhibition of septum formation, spheroplast formation, production of 'blisters', 'bulges' or mesosomes, as well as lysis and development of abnormally shaped cells. The incorporation of radioactively labelled diaminopimelic acid into the cell wall murein of strain W7, was inhibited by lemongrass oil in a dose dependent way. The sequence of changes induced by lemongrass oil on bacterial cell morphology and also its interference with murein synthesis in E. coli cells were interpreted to involve the penicillin binding proteins PBP 2 and PBP 3.     

Encapsulation of lemongrass oil with cyclodextrins by spray drying and its controlled release characteristics

Inclusion of the two isomers of citral (E-citral and Z-citral), components of lemongrass oil, was investigated within the confines of various cyclodextrin (α-CD, β-CD and γ-CD) host molecules. Aqueous complex formation constants for E-citral with α-CD, β-CD and γ-CD were determined to be 123, 185, and 204 L/mol, respectively, whereas Z-citral exhibited stronger affinities (157, 206, and 253 L/mol, respectively). The binding trend γ-CD > β-CD > α-CD is a reflection of the more favorable geometrical accommodation of the citral isomers with increasing cavity size. Encapsulation of lemongrass oil within CDs was undertaken through shaking citral:CD (1:1, 1.5:1, and 2:1 molar ratio) mixtures followed by spray drying. Maximum citral retention occurred at a 1:1 molar ratio with β-CD and α-CD demonstrating the highest levels of total E-citral and Z-citral retention, respectively. Furthermore, the β-CD complex demonstrated the slowest release rate of all inclusion complex powders.     

Inhibitory effect of lemongrass oil and its major constituents on Candida biofilm and germ tube formation

Adhesion to a variety of host cells and the surface of biomaterials is a critical step in successful colonization and infection by Candida spp. Several essential oils are known to possess antifungal properties and are potentially used as antifungal agents. By studying the efficacy of essential oils against different pathogenic fungi in the genus Candida, we have evaluated the in vitro antifungal effects of eight essential oils used in aromatherapy, namely holy basil (Ocimum sactum L), lemongrass (Cymbopogon citratus DC), citronella grass (Cymbopogon winterianus Jowitt), kaffir lime (Citrus hystrix DC), sweet basil (Ocimum basilicum Linn), Plai (Zingiber cassumunar Roxb), Curcuma (Curcuma longa Linn), and ginger (Zingiber officinale Rose), against Candida albicans and Candida krusei in both planktonic and biofilm form. The results revealed that among the tested essential oils, lemongrass oil exhibited the most effective killing activity and possessed the strongest inhibitory effect on Candida biofilm formation. In addition, lemongrass oil and its major constituents can inhibit germ tube formation, which might affect adherence. The data in this study indicates that lemongrass oil possessed antibiofilm activity and could modulate candidal colonization. Therefore, it is a promising essential oil to combat candidal colonization and infection.